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Filed Pursant to Rule 424(b)(5)
Registration No. 333-205298

CALCULATION OF REGISTRATION FEE

(1)

Calculated in accordance with Rule 457(r) of the Securities Act of 1933, as amended.     

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PROSPECTUS SUPPLEMENT
(To prospectus dated June 26, 2015)

Senior Housing Properties Trust

$500,000,000 4.750% Senior Notes Due 2028

COMPANY

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We are a real estate investment trust, or REIT, that owns independent and assisted senior living communities, continuing care retirement communities, skilled nursing facilities, wellness centers, and properties leased to medical providers, medical related businesses, clinics and biotech laboratory tenants located throughout the United States.

USE OF PROCEEDS

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We expect to use the net proceeds from this offering to reduce amounts outstanding under our revolving credit facility. See "Use of proceeds."

NOTES

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We are offering $500,000,000 aggregate principal amount of our 4.750% senior notes due 2028, or the notes.



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Interest on the notes will be payable semiannually on February 15 and August 15 of each year, commencing August 15, 2018.



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We may redeem the notes in whole at any time or in part from time to time before they mature at the applicable redemption price described in this prospectus supplement under the caption "Description of the notes—Optional Redemption of the Notes." If the notes are redeemed on or after August 15, 2027 (six months prior to their stated maturity date), the redemption price for the notes will not include a Make-Whole Amount (as defined herein).



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There is no sinking fund.



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The notes will be our senior unsecured obligations and will rank equally with all of our other existing and future unsecured senior indebtedness. The notes will be effectively subordinated to all liabilities of our subsidiaries and to our secured indebtedness. The notes will also be effectively subordinated to any preferred equity that our subsidiaries may issue.



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The notes constitute a new issue of securities with no established trading market and we do not intend to apply for listing of the notes on any securities exchange or for quotation of the notes on any automated dealer quotation system.

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          Investing in the notes involves risks that are described in the "Risk Factors" section of our Annual Report on Form 10-K for the year ended December 31, 2016, or our Annual Report.

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(1)

Plus accrued interest, if any, from the date the notes are issued, if settlement occurs after that date.

          Neither the Securities and Exchange Commission, or the SEC, nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

          The underwriters expect to deliver the notes to purchasers in book-entry form only through The Depository Trust Company on or about February 12, 2018.

Joint Book-Running Managers

Joint Lead Managers

Co-Managers

   

The date of this prospectus supplement is February 8, 2018.

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        References in this prospectus supplement to "we," "us," "our" and "SNH" mean Senior Housing Properties Trust and its consolidated subsidiaries, unless the context otherwise requires. References in this prospectus supplement to the "notes" mean the 4.750% senior notes due 2028 offered hereby.

        This prospectus supplement contains a description of the terms of the notes. A description of the indenture relating to our debt securities is set forth in the accompanying prospectus under the heading "Description of Debt Securities." This prospectus supplement, and the information incorporated by reference herein, may add, update or change information in the accompanying prospectus (or the information incorporated by reference therein). If information in this prospectus supplement is inconsistent with the accompanying prospectus, this prospectus supplement will apply and will supersede that information in the accompanying prospectus.

        It is important for you to read and consider all information contained in this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein in making your investment decision. You should also read and consider the information in the documents to which we have referred you in "Where you can find more information" in this prospectus supplement and the accompanying prospectus.

        You should rely only on the information contained or incorporated by reference in this prospectus supplement, the accompanying prospectus and any related free writing prospectus issued by us. We have not, and the underwriters have not, authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus and any related free writing prospectus issued by us, as well as information we previously filed with the SEC and incorporated by reference, is accurate only as of their respective dates. Our business, financial condition, results of operations, liquidity and prospects may have changed since those dates.

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INFORMATION INCORPORATED BY REFERENCE

        The SEC allows us to "incorporate by reference" the information we file with it, which means that we can disclose important information to you by referring you to documents previously filed with the SEC. The information incorporated by reference is considered to be part of this prospectus supplement and the accompanying prospectus, and information that we subsequently file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below which were filed with the SEC under the Securities Exchange Act of 1934, as amended, or the Exchange Act:

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Our Annual Report;



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Our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2017, June 30, 2017 and September 30, 2017;



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The information identified as incorporated by reference under Items 10, 11, 12, 13 and 14 of Part III of our Annual Report from our definitive Proxy Statement for our 2017 Annual Meeting of Shareholders filed with the SEC on February 28, 2017; and



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Our Current Reports on Form 8-K dated June 26, 2015, March 24, 2017 (Item 8.01 only), May 18, 2017, June 30, 2017 and January 19, 2018.

        We also incorporate by reference each of the following documents that we may file with the SEC after the date of this prospectus supplement but before the termination of the offering of the notes:

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Reports filed under Sections 13(a) and (c) of the Exchange Act;



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Definitive proxy or information statements filed under Section 14 of the Exchange Act in connection with any subsequent shareholders' meeting; and



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Any reports filed under Section 15(d) of the Exchange Act.

        You may request a copy of any of these filings (excluding exhibits other than those which we specifically incorporate by reference in this prospectus supplement or the accompanying prospectus), at no cost, by writing, emailing or telephoning us at the following address:

Investor Relations
Senior Housing Properties Trust
Two Newton Place
255 Washington Street, Suite 300
Newton, Massachusetts 02458-1634
(617) 796-8234
info@snhreit.com

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WARNING CONCERNING FORWARD LOOKING STATEMENTS

        THIS PROSPECTUS SUPPLEMENT, THE ACCOMPANYING PROSPECTUS, AND THE DOCUMENTS INCORPORATED HEREIN OR THEREIN BY REFERENCE CONTAIN STATEMENTS THAT CONSTITUTE FORWARD LOOKING STATEMENTS WITHIN THE MEANING OF THE PRIVATE SECURITIES LITIGATION REFORM ACT OF 1995 AND OTHER SECURITIES LAWS. ALSO, WHENEVER WE USE WORDS SUCH AS "BELIEVE," "EXPECT," "ANTICIPATE," "INTEND," "PLAN," "ESTIMATE," "WILL," "MAY" AND NEGATIVES OR DERIVATIVES OF THESE OR SIMILAR EXPRESSIONS, WE ARE MAKING FORWARD LOOKING STATEMENTS. THESE FORWARD LOOKING STATEMENTS ARE BASED UPON OUR PRESENT INTENT, BELIEFS OR EXPECTATIONS, BUT FORWARD LOOKING STATEMENTS ARE NOT GUARANTEED TO OCCUR AND MAY NOT OCCUR. FORWARD LOOKING STATEMENTS IN THIS PROSPECTUS SUPPLEMENT RELATE TO VARIOUS ASPECTS OF OUR BUSINESS, INCLUDING:

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OUR POLICIES AND PLANS REGARDING INVESTMENTS, FINANCINGS AND DISPOSITIONS,



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OUR ABILITY TO RETAIN OUR EXISTING TENANTS, ATTRACT NEW TENANTS AND MAINTAIN OR INCREASE CURRENT RENTAL RATES,



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THE CREDIT QUALITIES OF OUR TENANTS,



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OUR ABILITY TO COMPETE FOR ACQUISITIONS AND TENANCIES EFFECTIVELY,



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OUR ACQUISITIONS AND SALES OF PROPERTIES,



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THE ABILITY OF THE MANAGER OF OUR MANAGED SENIOR LIVING COMMUNITIES TO MAINTAIN AND INCREASE OCCUPANCY, REVENUES AND OPERATING INCOME AT THOSE COMMUNITIES,



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OUR ABILITY TO PAY DISTRIBUTIONS TO OUR SHAREHOLDERS AND TO SUSTAIN THE AMOUNT OF SUCH DISTRIBUTIONS,



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OUR ABILITY TO RAISE DEBT OR EQUITY CAPITAL,



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THE FUTURE AVAILABILITY OF BORROWINGS UNDER OUR REVOLVING CREDIT FACILITY,



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OUR ABILITY TO PAY INTEREST ON AND PRINCIPAL OF OUR DEBT,



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OUR ABILITY TO APPROPRIATELY BALANCE OUR USE OF DEBT AND EQUITY CAPITAL,



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OUR CREDIT RATINGS,



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OUR EXPECTATION THAT WE BENEFIT FROM OUR OWNERSHIP OF THE RMR GROUP INC., OR RMR INC.,



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OUR EXPECTATION THAT WE BENEFIT FROM OUR OWNERSHIP OF AFFILIATES INSURANCE COMPANY, OR AIC, AND FROM OUR PARTICIPATION IN INSURANCE PROGRAMS ARRANGED BY AIC,



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OUR QUALIFICATION FOR TAXATION AS A REIT,



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OUR BELIEF THAT THE AGING U.S. POPULATION AND INCREASING LIFE SPANS OF SENIORS WILL INCREASE THE DEMAND FOR SENIOR LIVING SERVICES,



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OUR BELIEF THAT FIVE STAR SENIOR LIVING INC., OR FIVE STAR, OUR FORMER SUBSIDIARY AND LARGEST TENANT AND THE MANAGER OF OUR MANAGED

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SENIOR LIVING COMMUNITIES, HAS ADEQUATE FINANCIAL RESOURCES AND LIQUIDITY AND THE ABILITY TO MEET ITS OBLIGATIONS TO US AND TO MANAGE OUR SENIOR LIVING COMMUNITIES SUCCESSFULLY,

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OUR EXPECTED USE OF PROCEEDS FROM THIS OFFERING, AND



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OTHER MATTERS.

        OUR ACTUAL RESULTS MAY DIFFER MATERIALLY FROM THOSE CONTAINED IN OR IMPLIED BY OUR FORWARD LOOKING STATEMENTS AS A RESULT OF VARIOUS FACTORS. FACTORS THAT COULD HAVE A MATERIAL ADVERSE EFFECT ON OUR FORWARD LOOKING STATEMENTS AND UPON OUR BUSINESS, RESULTS OF OPERATIONS, FINANCIAL CONDITION, FUNDS FROM OPERATIONS, NORMALIZED FUNDS FROM OPERATIONS, NOI, CASH BASIS NOI, CASH FLOWS, LIQUIDITY AND PROSPECTS INCLUDE, BUT ARE NOT LIMITED TO:

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THE IMPACT OF CONDITIONS AND CHANGES IN THE ECONOMY AND THE CAPITAL MARKETS ON US AND OUR TENANTS AND MANAGERS,



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THE IMPACT OF THE PATIENT PROTECTION AND AFFORDABLE CARE ACT, OR THE ACA AND OTHER EXISTING OR PROPOSED LEGISLATION OR REGULATIONS ON US, ON OUR TENANTS AND MANAGERS, AND ON THEIR ABILITY TO PAY OUR RENTS AND RETURNS,



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ACTUAL AND POTENTIAL CONFLICTS OF INTEREST WITH OUR RELATED PARTIES, INCLUDING OUR MANAGING TRUSTEES, FIVE STAR, RMR LLC, RMR INC., AIC AND OTHERS AFFILIATED WITH THEM,



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COMPLIANCE WITH, AND CHANGES TO, FEDERAL, STATE AND LOCAL LAWS AND REGULATIONS, ACCOUNTING RULES, TAX LAWS AND SIMILAR MATTERS,



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LIMITATIONS IMPOSED ON OUR BUSINESS AND OUR ABILITY TO SATISFY COMPLEX RULES IN ORDER FOR US TO QUALIFY FOR TAXATION AS A REIT FOR U.S. FEDERAL INCOME TAX PURPOSES,



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COMPETITION WITHIN THE HEALTHCARE AND REAL ESTATE INDUSTRIES, AND



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ACTS OF TERRORISM, OUTBREAKS OF SO CALLED PANDEMICS OR OTHER MANMADE OR NATURAL DISASTERS BEYOND OUR CONTROL.

        FOR EXAMPLE:

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FIVE STAR IS OUR LARGEST TENANT AND THE MANAGER OF OUR MANAGED SENIOR LIVING COMMUNITIES AND IT MAY EXPERIENCE FINANCIAL DIFFICULTIES AS A RESULT OF A NUMBER OF FACTORS, INCLUDING, BUT NOT LIMITED TO:



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CHANGES IN MEDICARE OR MEDICAID POLICIES, INCLUDING THOSE THAT MAY RESULT FROM THE ACA AND OTHER EXISTING OR PROPOSED LEGISLATION OR REGULATIONS, WHICH COULD RESULT IN REDUCED MEDICARE OR MEDICAID RATES OR A FAILURE OF SUCH RATES TO COVER FIVE STAR'S COSTS OR LIMIT THE SCOPE OR FUNDING OF EITHER OR BOTH PROGRAMS,



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THE IMPACT OF CHANGES IN THE ECONOMY AND THE CAPITAL MARKETS ON FIVE STAR AND ITS RESIDENTS AND OTHER CUSTOMERS,



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COMPETITION WITHIN THE SENIOR LIVING SERVICES BUSINESS,

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INCREASES IN TORT AND INSURANCE LIABILITY COSTS,



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INCREASES IN COMPLIANCE COSTS, AND



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INCREASES IN FIVE STAR'S LABOR COSTS OR IN COSTS FIVE STAR PAYS FOR GOODS AND SERVICES.



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IF FIVE STAR'S OPERATIONS CONTINUE TO BE UNPROFITABLE, IT MAY DEFAULT ON ITS RENT OBLIGATIONS TO US,



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IF FIVE STAR FAILS TO PROVIDE QUALITY SERVICES AT SENIOR LIVING COMMUNITIES THAT WE OWN, OUR INCOME FROM THESE COMMUNITIES MAY BE ADVERSELY AFFECTED,



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IN RESPONSE TO COMPETITIVE PRESSURES RESULTING FROM RECENT AND EXPECTED NEW SUPPLY OF SENIOR LIVING COMMUNITIES, WE HAVE BEEN INVESTING IN IMPROVEMENTS TO OUR EXISTING SENIOR LIVING COMMUNITIES. OUR COMMUNITIES MAY FAIL TO BE COMPETITIVE AND THEY MAY FAIL TO ATTRACT RESIDENTS, DESPITE OUR CAPITAL INVESTMENTS,



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OUR OTHER TENANTS MAY EXPERIENCE LOSSES AND DEFAULT ON THEIR RENT OBLIGATIONS TO US,



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SOME OF OUR TENANTS MAY NOT RENEW EXPIRING LEASES, AND WE MAY BE UNABLE TO OBTAIN NEW TENANTS TO MAINTAIN OR INCREASE THE HISTORICAL OCCUPANCY RATES OF, OR RENTS FROM, OUR PROPERTIES,



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OUR ABILITY TO MAKE FUTURE DISTRIBUTIONS TO OUR SHAREHOLDERS AND TO MAKE PAYMENTS OF PRINCIPAL AND INTEREST ON OUR INDEBTEDNESS DEPENDS UPON A NUMBER OF FACTORS, INCLUDING OUR FUTURE EARNINGS, THE CAPITAL COSTS WE INCUR TO LEASE AND OPERATE OUR PROPERTIES AND OUR WORKING CAPITAL REQUIREMENTS. WE MAY BE UNABLE TO PAY OUR DEBT OBLIGATIONS OR TO MAINTAIN OUR CURRENT RATE OF DISTRIBUTIONS ON OUR COMMON SHARES AND FUTURE DISTRIBUTIONS MAY BE REDUCED OR ELIMINATED,



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OUR ABILITY TO GROW OUR BUSINESS AND INCREASE OUR DISTRIBUTIONS DEPENDS IN LARGE PART UPON OUR ABILITY TO BUY PROPERTIES AND ARRANGE FOR THEIR PROFITABLE OPERATION OR LEASE THEM FOR RENTS, LESS THEIR PROPERTY OPERATING EXPENSES, THAT EXCEED OUR CAPITAL COSTS. WE MAY BE UNABLE TO IDENTIFY PROPERTIES THAT WE WANT TO ACQUIRE OR TO NEGOTIATE ACCEPTABLE PURCHASE PRICES, ACQUISITION FINANCING, MANAGEMENT CONTRACTS OR LEASE TERMS FOR NEW PROPERTIES,



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RENTS THAT WE CAN CHARGE AT OUR PROPERTIES MAY DECLINE BECAUSE OF CHANGING MARKET CONDITIONS OR OTHERWISE,



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CONTINGENCIES IN OUR ACQUISITION AND SALE AGREEMENTS MAY NOT BE SATISFIED AND OUR PENDING ACQUISITIONS AND SALES AND ANY RELATED LEASES OR MANAGEMENT ARRANGEMENTS WE MAY EXPECT TO ENTER INTO MAY NOT OCCUR, MAY BE DELAYED OR THE TERMS OF SUCH TRANSACTIONS OR ARRANGEMENTS MAY CHANGE,



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WE PREVIOUSLY AGREED TO ACQUIRE SIX SENIOR LIVING COMMUNITIES FROM FIVE STAR FOR APPROXIMATELY $104.0 MILLION, INCLUDING OUR ASSUMPTION OF APPROXIMATELY $34.0 MILLION OF MORTGAGE DEBT

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SECURING CERTAIN OF THESE SENIOR LIVING COMMUNITIES AND EXCLUDING CLOSING COSTS, AND TO ENTER MANAGEMENT AND POOLING ARRANGEMENTS WITH FIVE STAR FOR THESE SENIOR LIVING COMMUNITIES. IN DECEMBER 2017 AND JANUARY 2018, WE ACQUIRED, AND FIVE STAR BEGAN MANAGING, TWO AND ONE OF THESE SENIOR LIVING COMMUNITIES, RESPECTIVELY, FOR APPROXIMATELY $58.8 MILLION. THE REMAINING ACQUISITIONS ARE EXPECTED TO OCCUR AS THIRD PARTY APPROVALS ARE RECEIVED BETWEEN NOW AND THE END OF THE FIRST QUARTER OF 2018. RECEIPT OF THESE APPROVALS MAY BE DELAYED OR MAY NOT BE OBTAINED. THESE ACQUISITIONS ARE SUBJECT TO OTHER CONDITIONS AS WELL; THESE CONDITIONS MAY NOT BE MET AND SOME OR ALL OF THESE ACQUISITIONS MAY NOT BE COMPLETED, MAY BE DELAYED OR THE TERMS OF THESE ACQUISITIONS OR THE MANAGEMENT AND POOLING ARRANGEMENTS FOR THESE COMMUNITIES MAY CHANGE.

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WE PREVIOUSLY AGREED TO SELL THREE SENIOR LIVING COMMUNITIES CURRENTLY LEASED TO SUNRISE FOR $313.0 MILLION, EXCLUDING CLOSING COSTS. THESE SALES ARE EXPECTED TO BE COMPLETED BEFORE MARCH 31, 2018; HOWEVER, THESE SALES ARE SUBJECT TO CONDITIONS WHICH MAY NOT BE MET AND SOME OR ALL OF THESE SALES MAY NOT BE COMPLETED, MAY BE DELAYED OR THE TERMS OF THESE SALES MAY CHANGE.



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WE EXPECT TO ENTER INTO ADDITIONAL LEASE OR MANAGEMENT ARRANGEMENTS WITH FIVE STAR FOR ADDITIONAL SENIOR LIVING COMMUNITIES THAT WE OWN OR MAY ACQUIRE IN THE FUTURE. HOWEVER, WE CANNOT BE SURE THAT WE WILL ENTER INTO ANY ADDITIONAL LEASES, MANAGEMENT ARRANGEMENTS OR OTHER TRANSACTIONS WITH FIVE STAR,



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CONTINUED AVAILABILITY OF BORROWINGS UNDER OUR REVOLVING CREDIT FACILITY IS SUBJECT TO OUR SATISFYING CERTAIN FINANCIAL COVENANTS AND OTHER CREDIT FACILITY CONDITIONS THAT WE MAY BE UNABLE TO SATISFY,



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ACTUAL COSTS UNDER OUR REVOLVING CREDIT FACILITY OR OTHER FLOATING RATE DEBT WILL BE HIGHER THAN LIBOR PLUS A PREMIUM BECAUSE OF FEES AND EXPENSES ASSOCIATED WITH SUCH DEBT,



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THE MAXIMUM BORROWING AVAILABILITY UNDER OUR REVOLVING CREDIT FACILITY AND TERM LOANS MAY BE INCREASED TO UP TO $3.1 BILLION ON A COMBINED BASIS IN CERTAIN CIRCUMSTANCES. HOWEVER, INCREASING THE MAXIMUM BORROWING AVAILABILITY UNDER OUR REVOLVING CREDIT FACILITY AND TERM LOANS IS SUBJECT TO OUR OBTAINING ADDITIONAL COMMITMENTS FROM LENDERS, WHICH MAY NOT OCCUR,



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WE HAVE THE OPTION TO EXTEND THE MATURITY DATE OF OUR REVOLVING CREDIT FACILITY UPON PAYMENT OF A FEE AND MEETING OTHER CONDITIONS; HOWEVER, THE APPLICABLE CONDITIONS MAY NOT BE MET,



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THE PREMIUMS USED TO DETERMINE THE INTEREST RATE PAYABLE ON OUR REVOLVING CREDIT FACILITY AND TERM LOANS AND THE FACILITY FEE PAYABLE ON OUR REVOLVING CREDIT FACILITY ARE BASED ON OUR CREDIT RATINGS. FUTURE CHANGES IN OUR CREDIT RATINGS MAY CAUSE THE INTEREST AND FEES WE PAY TO INCREASE,



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WE MAY BE UNABLE TO REPAY OUR DEBT OBLIGATIONS WHEN THEY BECOME DUE,

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FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2017, APPROXIMATELY 97% OF OUR NOI WAS GENERATED FROM PROPERTIES WHERE A MAJORITY OF THE REVENUES ARE DERIVED FROM OUR TENANTS' AND RESIDENTS' PRIVATE RESOURCES. THIS MAY IMPLY THAT WE WILL MAINTAIN OR INCREASE THE PERCENTAGE OF OUR NOI GENERATED FROM PRIVATE RESOURCES AT OUR SENIOR LIVING COMMUNITIES. HOWEVER, OUR RESIDENTS AND PATIENTS MAY BECOME UNABLE TO FUND OUR CHARGES WITH PRIVATE RESOURCES AND WE MAY BE REQUIRED OR MAY ELECT FOR BUSINESS REASONS TO ACCEPT OR PURSUE REVENUES FROM GOVERNMENT SOURCES, WHICH COULD RESULT IN AN INCREASED PART OF OUR NOI AND REVENUE BEING GENERATED FROM GOVERNMENT PAYMENTS AND OUR BECOMING MORE DEPENDENT ON GOVERNMENT PAYMENTS,



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CIRCUMSTANCES THAT ADVERSELY AFFECT THE ABILITY OF SENIORS OR THEIR FAMILIES TO PAY FOR OUR TENANTS' AND MANAGER'S SERVICES, SUCH AS ECONOMIC DOWNTURNS, WEAK HOUSING MARKET CONDITIONS, HIGHER LEVELS OF UNEMPLOYMENT AMONG OUR RESIDENTS' FAMILY MEMBERS, LOWER LEVELS OF CONSUMER CONFIDENCE, STOCK MARKET VOLATILITY AND/OR CHANGES IN DEMOGRAPHICS GENERALLY COULD AFFECT THE PROFITABILITY OF OUR SENIOR LIVING COMMUNITIES,



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AS OF SEPTEMBER 30, 2017, WE HAD ESTIMATED UNSPENT LEASING RELATED OBLIGATIONS OF $21.6 MILLION. IT IS DIFFICULT TO ACCURATELY ESTIMATE TENANT SPACE PREPARATION COSTS. OUR UNSPENT LEASING RELATED OBLIGATIONS MAY COST MORE OR LESS AND MAY TAKE LONGER TO COMPLETE THAN WE CURRENTLY EXPECT, AND WE MAY INCUR INCREASING AMOUNTS FOR THESE AND SIMILAR PURPOSES IN THE FUTURE,



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WE MAY NOT BE ABLE TO SELL PROPERTIES THAT WE DETERMINE TO OFFER FOR SALE ON TERMS ACCEPTABLE TO US OR OTHERWISE,



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WE BELIEVE THAT OUR RELATIONSHIPS WITH OUR RELATED PARTIES, INCLUDING FIVE STAR, RMR LLC, RMR INC., ABP TRUST, AIC AND OTHERS AFFILIATED WITH THEM MAY BENEFIT US AND PROVIDE US WITH COMPETITIVE ADVANTAGES IN OPERATING AND GROWING OUR BUSINESS. HOWEVER, THE ADVANTAGES WE BELIEVE WE MAY REALIZE FROM THESE RELATIONSHIPS MAY NOT MATERIALIZE,



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RMR INC. MAY REDUCE THE AMOUNT OF ITS DISTRIBUTIONS TO ITS SHAREHOLDERS, INCLUDING US,



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OUR SENIOR LIVING COMMUNITIES ARE SUBJECT TO EXTENSIVE GOVERNMENT REGULATION, LICENSURE AND OVERSIGHT. WE SOMETIMES EXPERIENCE DEFICIENCIES IN THE OPERATION OF OUR SENIOR LIVING COMMUNITIES AND SOME OF OUR COMMUNITIES MAY BE PROHIBITED FROM ADMITTING NEW RESIDENTS OR OUR LICENSE TO CONTINUE OPERATIONS AT A COMMUNITY MAY BE REVOKED. ALSO, OPERATING DEFICIENCIES OR A LICENSE REVOCATION AT ONE OR MORE OF OUR SENIOR LIVING COMMUNITIES MAY HAVE AN ADVERSE IMPACT ON OUR ABILITY TO OBTAIN LICENSES FOR, OR ATTRACT RESIDENTS TO, OUR OTHER COMMUNITIES,



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THE BUSINESS AND PROPERTY MANAGEMENT AGREEMENTS BETWEEN US AND RMR LLC HAVE CONTINUING 20 YEAR TERMS. HOWEVER, THOSE AGREEMENTS PERMIT EARLY TERMINATION IN CERTAIN CIRCUMSTANCES. ACCORDINGLY, WE

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CANNOT BE SURE THAT THESE AGREEMENTS WILL REMAIN IN EFFECT FOR CONTINUING 20 YEAR TERMS,

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OUR CURRENT INTENT TO REDUCE AMOUNTS OUTSTANDING UNDER OUR REVOLVING CREDIT FACILITY WITH THE NET PROCEEDS FROM THE OFFERING OF THE NOTES IS DEPENDENT ON THE CLOSING OF THE OFFERING AND MAY NOT OCCUR, AND



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THIS PROSPECTUS SUPPLEMENT STATES THAT WE EXPECT TO ISSUE AND DELIVER THE NOTES ON OR ABOUT FEBRUARY 12, 2018. IN FACT, THE ISSUANCE AND DELIVERY OF THE NOTES IS SUBJECT TO VARIOUS CONDITIONS AND CONTINGENCIES AS ARE CUSTOMARY IN UNDERWRITING AGREEMENTS IN THE UNITED STATES. IF THESE CONDITIONS ARE NOT SATISFIED OR THE SPECIFIED CONTINGENCIES DO NOT OCCUR, THIS OFFERING MAY BE DELAYED OR MAY NOT BE COMPLETED.

        CURRENTLY UNEXPECTED RESULTS COULD OCCUR DUE TO MANY DIFFERENT CIRCUMSTANCES, SOME OF WHICH ARE BEYOND OUR CONTROL, SUCH AS NEW LEGISLATION OR REGULATIONS AFFECTING OUR BUSINESS OR THE BUSINESSES OF OUR TENANTS OR MANAGERS, CHANGES IN OUR TENANTS' OR MANAGERS' REVENUES OR COSTS, CHANGES IN OUR TENANTS' OR MANAGERS' FINANCIAL CONDITIONS, DEFICIENCIES IN OPERATIONS BY A TENANT OR MANAGER OF ONE OR MORE OF OUR SENIOR LIVING COMMUNITIES, CHANGED MEDICARE OR MEDICAID RATES, ACTS OF TERRORISM, NATURAL DISASTERS OR CHANGES IN CAPITAL MARKETS OR THE ECONOMY GENERALLY.

        THE INFORMATION CONTAINED ELSEWHERE IN THIS PROSPECTUS SUPPLEMENT AND IN OUR FILINGS WITH THE SEC, INCLUDING UNDER THE CAPTION "RISK FACTORS," OR INCORPORATED HEREIN OR THEREIN, IDENTIFIES OTHER IMPORTANT FACTORS THAT COULD CAUSE DIFFERENCES FROM OUR FORWARD LOOKING STATEMENTS. OUR FILINGS WITH THE SEC ARE AVAILABLE ON THE SEC'S WEBSITE AT WWW.SEC.GOV.

        YOU SHOULD NOT PLACE UNDUE RELIANCE UPON OUR FORWARD LOOKING STATEMENTS.

        EXCEPT AS REQUIRED BY LAW, WE DO NOT INTEND TO UPDATE OR CHANGE ANY FORWARD LOOKING STATEMENTS AS A RESULT OF NEW INFORMATION, FUTURE EVENTS OR OTHERWISE.

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USE OF PROCEEDS

        We estimate that our net proceeds from this offering will be approximately $487.6 million after payment of the underwriting discount and other estimated offering expenses payable by us. We expect to use the net proceeds from this offering to reduce amounts outstanding under our revolving credit facility. Pending such application, we may invest the net proceeds in short term investments, some or all of which may not be investment grade rated.

        The amounts outstanding under our revolving credit facility were incurred, in part, for general business purposes, including to fund acquisitions and to prepay certain mortgage debt. Our revolving credit facility bears interest at LIBOR plus a premium and matures on January 15, 2022. At February 7, 2018, there was $717.0 million outstanding under our revolving credit facility and the interest rate was 2.7% per annum.

        Affiliates of some of the underwriters are lenders under our revolving credit facility and will receive pro rata portions of the net proceeds from this offering used to reduce amounts outstanding thereunder. See "Underwriting (Conflicts of interest)—Conflicts of Interest."

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RATIO OF EARNINGS TO FIXED CHARGES

        The following table sets forth our ratio of earnings to fixed charges for each of the periods shown.

        For purposes of calculating the ratios above, earnings have been calculated by adding fixed charges to income from continuing operations (including gains on sales of properties, if any) before income tax expense and equity in earnings (losses) of an investee. Fixed charges consist of interest expense (including net amortization of debt premiums and discounts and debt issuance costs).

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DESCRIPTION OF THE NOTES

        The following description of the particular terms of the notes supplements and, to the extent inconsistent with, replaces the description of the general terms and provisions of debt securities set forth under "Description of Debt Securities" in the accompanying prospectus. Definitions of certain capitalized words used in discussing the terms of the notes appear below under "Description of the Notes—Certain Defined Terms." References in this section and in the defined terms to "SNH," "we," "our," and "us" mean Senior Housing Properties Trust and not its subsidiaries.

General

        We will issue the notes under a base indenture dated as of February 18, 2016 and a supplemental indenture thereto, together, the Indenture, between us and U.S. Bank National Association, as trustee, or the Trustee. The Indenture is subject to, and governed by, the Trust Indenture Act of 1939, as amended. This prospectus supplement briefly summarizes some of the provisions of the Indenture. This summary is not complete. If you would like more information on these provisions, review the copy of our base indenture dated February 18, 2016 that we have filed with the SEC and the supplemental indenture thereto relating to the notes that we will file with the SEC. See "Information incorporated by reference" and "Where you can find more information" in this prospectus supplement and "Information incorporated by reference" and "Where you can find more information" in the accompanying prospectus for information about how to locate these documents. You may also review the Indenture at the Trustee's corporate trust office at One Federal Street, 3^rd Floor, Boston, Massachusetts 02110.

        The notes will be a separate series under the Indenture, initially in the aggregate principal amount of $500,000,000. The Indenture does not limit the amount of debt securities that we may issue under the Indenture, and we may issue debt securities in one or more series up to the aggregate initial offering price authorized by us for each series. We may, without the consent of the holders of the notes, reopen this series of notes and issue additional notes under the Indenture in addition to the notes initially authorized as of the date of this prospectus supplement. Any additional notes of this series will have the same terms as the notes offered by this prospectus supplement, except for issue date, issue price and, if applicable, date of the first payment of interest thereon and related interest accrual date. Any additional notes of this series would rank equally with the notes offered hereby; provided that if such additional notes are not fungible with the notes offered hereby for U.S. federal income tax purposes, or to the extent required by applicable securities laws or regulations or procedures of The Depository Trust Company, or DTC, such additional notes would have a different CUSIP number. Unless the context otherwise requires, references herein to "notes" are deemed to include any additional notes actually issued, to the extent appropriate.

        The notes will mature on February 15, 2028 (unless previously redeemed). The notes will be issued only in fully registered form without coupons, in denominations of $2,000 and integral multiples of $1,000 in excess thereof. The notes will be evidenced by a global note in book-entry form, except under the limited circumstances described below under "—Book-Entry System and Form of Notes."

        The notes will be our senior unsecured obligations and will rank equally with all of our other existing and future unsecured and unsubordinated indebtedness outstanding from time to time. The notes will not be guaranteed by our subsidiaries. The notes will be effectively subordinated to our mortgages and other secured indebtedness, if any, and to all indebtedness and other liabilities and any preferred equity of our subsidiaries. Accordingly, such senior obligations will have to be satisfied in full before you will be able to realize any value from our secured or indirectly held properties.

        As of February 8, 2018, on an adjusted basis after giving effect to the issuance of the notes and the application of the net proceeds thereof as described herein under "Use of Proceeds," our total outstanding indebtedness would have been approximately $3.8 billion. As of such date, total

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indebtedness of our subsidiaries was approximately $817.0 million. We and our subsidiaries may incur additional indebtedness, including secured indebtedness, subject to the provisions described below under "—Certain Covenants—Limitations on Incurrence of Debt."

        Except as described under "—Certain Covenants" in this prospectus supplement and "Description of Debt Securities—Merger, Consolidation or Sale of Assets" in the accompanying prospectus, the Indenture does not contain any other provisions that would afford you protection in the event of (1) a highly leveraged or similar transaction involving us or any of our affiliates, (2) a change of control, or (3) a reorganization, restructuring, merger or similar transaction involving us that may adversely affect you. In addition, subject to the limitations set forth under "—Certain Covenants" in this prospectus supplement and "Description of Debt Securities—Merger, Consolidation or Sale of Assets" in the accompanying prospectus, we may enter into certain transactions such as the sale of all or substantially all of our assets or a merger or consolidation that would increase the amount of our indebtedness or substantially reduce or eliminate our assets, which might have an adverse effect on our ability to service our indebtedness, including the notes. We have no present intention of engaging in a highly leveraged or similar transaction.

Interest and Maturity

        The notes will bear interest at the rate per annum set forth on the cover page of this prospectus supplement from the date the notes are issued, which we expect will be February 12, 2018, or from the immediately preceding Interest Payment Date (as defined below) to which interest has been paid. Interest on the notes is payable semiannually in arrears on February 15 and August 15 of each year, or the Interest Payment Dates, beginning on August 15, 2018, to the persons in whose names the notes are registered at the close of business on February 1 or August 1, as the case may be, immediately preceding the applicable Interest Payment Date, or the Regular Record Date, regardless of whether the Regular Record Date is a Business Day. Accrued interest is also payable on the date of maturity or earlier redemption of the notes. Interest on the notes will be computed on the basis of a 360-day year consisting of twelve 30-day months. Unless previously redeemed, the notes will mature on February 15, 2028. If any Interest Payment Date, stated maturity date or redemption date falls on a day that is not a Business Day, the payment will be made on the next Business Day and no interest will accrue for the period from and after such Interest Payment Date, stated maturity date or redemption date.

        Payments of principal, premium, if any, and interest to holders of book-entry interests in the notes in global form will be made in accordance with the procedures of DTC and its participants in effect from time to time. See "—Book-Entry System and Form of Notes" below and "Description of Debt Securities—Global Debt Securities" in the accompanying prospectus.

Optional Redemption of the Notes

        We may redeem the notes at our option in whole or in part at any time and from time to time before they mature. The redemption price will equal the outstanding principal amount of the notes being redeemed, plus accrued and unpaid interest, if any, from the date of initial issuance, or the most recent date to which interest has been paid or provided for, whichever is later, to, but not including, the redemption date, plus the Make-Whole Amount, if any. If the notes are redeemed on or after August 15, 2027 (six months prior to their stated maturity date), the Make-Whole Amount will equal zero.

        We are required to give notice of such a redemption not less than 30 days nor more than 60 days prior to the redemption date to each holder's address appearing in the securities register maintained by the Trustee or, in the case of book-entry interests in notes in global form, in accordance with the procedures of DTC and its participants in effect from time to time. In the event we elect to redeem less than all of the notes, the particular notes to be redeemed will be selected by the Trustee by such

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method as the Trustee shall deem appropriate and in accordance with the procedures of DTC and its participants in effect from time to time. See "—Book-Entry System and Form of Notes" below and "Description of Debt Securities—Global Debt Securities" in the accompanying prospectus.

        We are not required to make any sinking fund or redemption payments prior to the stated maturity of the notes.

Certain Covenants

        Limitations on Incurrence of Debt.    SNH will not, and will not permit any Subsidiary to, incur any Debt if, immediately after giving effect to the incurrence of such additional Debt and the application of the proceeds therefrom, the aggregate principal amount of all outstanding Debt of SNH and its Subsidiaries on a consolidated basis determined in accordance with GAAP is greater than 60% of the sum of (without duplication):

        (1)   the Total Assets of SNH and its Subsidiaries as of the end of the fiscal quarter covered by SNH's Annual Report on Form 10-K, or its Quarterly Report on Form 10-Q, as the case may be, most recently filed with the SEC (or, if such filing is not permitted or required under the Securities Exchange Act of 1934, as amended, or the Exchange Act, with the Trustee) prior to the incurrence of such additional Debt; and

        (2)   the purchase price of any real estate assets or mortgages receivable acquired, and the amount of any securities offering proceeds received (to the extent that such proceeds were not used to acquire real estate assets or mortgages receivable or used to reduce Debt), by SNH or any Subsidiary since the end of such fiscal quarter, including those proceeds obtained in connection with the incurrence of such additional Debt.

The sum of (1) and (2) is our "Adjusted Total Assets."

        SNH will not, and will not permit any Subsidiary to, incur any Secured Debt if, immediately after giving effect to the incurrence of such additional Secured Debt and the application of the proceeds therefrom, the aggregate principal amount of all outstanding Secured Debt of SNH and its Subsidiaries on a consolidated basis determined in accordance with GAAP is greater than 40% of Adjusted Total Assets.

        SNH will not, and will not permit any Subsidiary to, incur any Debt if, immediately after giving effect to the incurrence of such additional Debt and on a pro forma basis, including the application of the proceeds therefrom, the ratio of Consolidated Income Available for Debt Service to the Annual Debt Service for the four consecutive fiscal quarters most recently ended prior to the date on which such additional Debt is to be incurred is less than 1.5 to 1.0, calculated on the assumptions that:

        (1)   such Debt and any other Debt incurred by SNH and its Subsidiaries on a consolidated basis since the first day of such four-quarter period and the application of the proceeds therefrom, including to refinance other Debt, had occurred at the beginning of such period,

        (2)   the repayment, retirement or other discharge of any other Debt by SNH and its Subsidiaries on a consolidated basis since the first day of such four-quarter period had occurred at the beginning of such period (except that, in making such computation, the amount of Debt under any revolving credit facility shall be computed based upon the average daily balance of such Debt during such period),

        (3)   in the case of Acquired Debt or Debt incurred in connection with or in contemplation of any acquisition, including any Person becoming a Subsidiary, since the first day of such four-quarter period, the related acquisition had occurred as of the first day of such period with appropriate adjustments with respect to such acquisition being included in such pro forma calculation, and

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        (4)   in the case of any acquisition or disposition by SNH and its Subsidiaries on a consolidated basis of any asset or group of assets since the first day of such four-quarter period, whether by merger, stock purchase or sale, or asset purchase or sale, such acquisition or disposition or any related repayment of Debt had occurred as of the first day of such period with the appropriate adjustments with respect to such acquisition or disposition being included in such pro forma calculation.

        If the Debt giving rise to the need to make the foregoing calculation or any other Debt incurred after the first day of the relevant four-quarter period bears interest at a floating interest rate, then, for purposes of calculating the Annual Debt Service, the interest rate on such Debt will be computed on a pro forma basis as if the average interest rate which would have been in effect during the entirety of such four-quarter period had been the applicable rate for the entirety of such period.

        Maintenance of Total Unencumbered Assets.    SNH and its Subsidiaries will at all times maintain Total Unencumbered Assets of not less than 150% of the aggregate outstanding principal amount of the Unsecured Debt of SNH and its Subsidiaries on a consolidated basis in accordance with GAAP.

        Provision of Financial Information.    Whether or not SNH remains required to do so under the Exchange Act, it will transmit by mail to all holders, without cost, and file with the Trustee copies of all annual, quarterly and other reports and financial statements it would have been required to file with the SEC pursuant to the Exchange Act and promptly upon written request and payment of the reasonable cost of duplication and delivery, supply copies of such documents to any prospective holder; provided that SNH may satisfy the foregoing requirements by making the materials available on the SEC's EDGAR system or on SNH's website within the time periods specified in the Indenture. If the notes become guaranteed by any direct or indirect parent company of SNH, SNH may satisfy its obligations under this covenant with respect to financial information relating to SNH by furnishing financial information relating to such direct or indirect parent company.

Merger, Consolidation or Sale of Assets

        The provisions of the Indenture relating to certain mergers and consolidations, and certain sales of our assets, described under "Description of Debt Securities—Merger, Consolidation or Sale of Assets" in the accompanying prospectus will apply to the notes.

Events of Default, Notice and Waiver

        The Indenture provides that the following events are "events of default" with respect to the notes:

(1)

default in the payment of principal of or any premium on the notes when due and payable;



(2)

default for 30 days in the payment of any installment of interest payable on the notes when due and payable;



(3)

default in the performance of, or breach of, any covenant of SNH contained in the Indenture with respect to the notes (not including a covenant added to the Indenture solely for the benefit of a series of debt other than the notes), which continues for 60 days after SNH receives a notice of default or breach as provided in the Indenture stating SNH is in default or breach and requiring that it be remedied;



(4)

default under any bond, debenture, note or other evidence of indebtedness of SNH, or under any mortgage, indenture or other instrument of SNH (including a default with respect to debt securities issued under the Indenture other than the notes) under which there may be issued or by which there may be secured any indebtedness of SNH (or by any subsidiary, the repayment of which SNH has guaranteed or for which SNH is directly responsible or liable as obligor or guarantor), whether such indebtedness now exists or is created by the Indenture,

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which default constitutes a failure to pay an aggregate principal amount exceeding $50 million after the expiration of any applicable grace period, and which default results in the acceleration of the maturity of such indebtedness; such default is not an event of default if the other indebtedness is discharged, or the acceleration is rescinded or annulled, within a period of 10 days after SNH receives notice as provided in the Indenture specifying the default and requiring that SNH discharge the other indebtedness or cause the acceleration to be rescinded or annulled; or

(5)

certain specified events of bankruptcy, insolvency or reorganization, or court appointment of a receiver, liquidator or trustee of SNH or any Significant Subsidiary or for all or substantially all of either of their property.

        Upon acceleration of the notes in accordance with the terms of the Indenture following the occurrence of an event of default, the principal amount of the notes, plus accrued and unpaid interest thereon, will become due and payable. See "Description of Debt Securities—Events of Default and Related Matters" in the accompanying prospectus for a description of rights, remedies and other matters relating to events of default.

Modification of the Indenture and Notes

        The Indenture and debt securities issued thereunder, including the notes described in this prospectus supplement, may be amended or otherwise changed in various circumstances, in some cases without the consent of holders of those debt securities and in some cases subject to the consent of some or all affected holders, as described under "Description of Debt Securities—Modification of an Indenture" in the accompanying prospectus.

Discharge, Defeasance and Covenant Defeasance

        The provisions of the Indenture relating to defeasance and covenant defeasance described under "Description of Debt Securities—Discharge, Defeasance and Covenant Defeasance" in the accompanying prospectus will apply to the notes.

Book-Entry System and Form of Notes

        The notes will initially be issued in the form of one or more fully registered global notes without coupons that will be deposited with or on behalf of DTC and registered in the name of its nominee, Cede & Co. This means that we will not issue certificates to each holder of notes. Each global note will be issued to DTC, which will keep a computerized record of its participants (for example, your broker) whose clients have purchased the notes. The participant will then keep a record of its clients who purchased the notes. Unless it is exchanged in whole or in part for a certificated note, each global note may not be transferred, except that DTC, its nominees, and their successors may transfer a global note in whole to one another. Beneficial interests in a global note will be shown on, and transfers of a global note will be made only through, records maintained by DTC and its participants. Additional information about notes in global form, DTC and the book-entry system is contained in the accompanying prospectus under the heading "Description of Debt Securities—Global Debt Securities."

Certain Defined Terms

        The following defined terms relate only to, and should be read in conjunction with the description of, the notes.

        "Acquired Debt" means Debt of a Person (1) existing at the time such Person becomes a Subsidiary or (2) assumed in connection with the acquisition of assets from such Person, in each case, other than Debt incurred in connection with, or in contemplation of, such Person becoming a Subsidiary or such

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acquisition. Acquired Debt is deemed to be incurred on the date of the related acquisition of assets from any Person or the date the acquired Person becomes a Subsidiary.

        "Adjusted Total Assets" is defined above under "—Certain Covenants—Limitations on Incurrence of Debt."

        "Affiliate" of any specified Person means any other Person directly or indirectly controlling or controlled by or under direct or indirect common control with such specified Person. For the purposes of this definition, "control" when used with respect to any specified Person means the power to direct the management and policies of such Person, directly or indirectly, whether through the ownership of voting securities, by contract or otherwise; and the terms "controlling" and "controlled" have meanings correlative to the foregoing.

        "Annual Debt Service" as of any date means the maximum amount which is expensed in any 12-month period for interest on Debt of SNH and its Subsidiaries, excluding amortization of debt discounts and deferred financing costs.

        "Business Day" means any day other than a Saturday or Sunday or a day on which banking institutions in The City of New York or in the city in which the corporate trust office of the Trustee is located are required or authorized to close.

        "Capital Stock" means, with respect to any Person, any capital stock (including preferred stock), shares, interests, participation or other ownership interests (however designated) of such Person and any rights (other than debt securities convertible into or exchangeable for capital stock), warrants or options to purchase any thereof.

        "Cash Equivalents" means demand deposits, certificates of deposit or repurchase agreements with banks or other financial institutions, marketable obligations issued or directly and fully guaranteed as to timely payment by the United States of America or any of its agencies or instrumentalities, or any commercial paper or other obligation rated, at time of purchase, "P-2" (or its equivalent) or better by Moody's or "A-2" (or its equivalent) or better by Standard & Poor's.

        "Consolidated Income Available for Debt Service" for any period means Earnings from Operations of SNH and its Subsidiaries plus amounts which have been deducted, and minus amounts which have been added, for the following (without duplication): (1) interest or distributions on Debt of SNH and its Subsidiaries, (2) provision for taxes of SNH and its Subsidiaries based on income, (3) amortization of debt discounts and deferred financing costs, (4) provisions for gains and losses on properties and property depreciation and amortization, (5) the effect of any noncash charge resulting from a change in accounting principles in determining Earnings from Operations for such period and (6) amortization of deferred charges.

        "Debt" of SNH or any Subsidiary means, without duplication, any indebtedness of SNH or any Subsidiary, whether or not contingent, in respect of:

        (1)   borrowed money or evidenced by bonds, notes, debentures or similar instruments,

        (2)   borrowed money secured by any Encumbrance existing on property owned by SNH or any Subsidiary, to the extent of the lesser of (x) the amount of indebtedness so secured or (y) the fair market value of the property subject to such Encumbrance,

        (3)   the reimbursement obligations, contingent or otherwise, in connection with any letters of credit actually issued (other than letters of credit issued to provide credit enhancement or support with respect to other indebtedness of SNH or any Subsidiary otherwise reflected as Debt hereunder) or amounts representing the balance deferred and unpaid of the purchase price of any property or services, except any such balance that constitutes an accrued expense or trade payable, or all conditional sale obligations or obligations under any title retention agreement,

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        (4)   the principal amount of all obligations of SNH or any Subsidiary with respect to redemption, repayment or other repurchase of any Disqualified Stock, or

        (5)   any lease of property by SNH or any Subsidiary as lessee which is reflected on SNH's consolidated balance sheet as a capitalized lease in accordance with GAAP,

to the extent, in the case of items of indebtedness under (1) through (5) above, that any such items (other than letters of credit) would be properly classified as a liability on SNH's consolidated balance sheet in accordance with GAAP. Debt also (1) excludes any indebtedness (A) with respect to which a defeasance or covenant defeasance or discharge has been effected (or an irrevocable deposit is made with a trustee in an amount at least equal to the outstanding principal amount of such indebtedness, the remaining scheduled payments of interest thereon to, but not including, the applicable maturity date or redemption date, and any premium or otherwise as provided in the terms of such indebtedness) in accordance with the terms thereof or which has been repurchased, retired, repaid, redeemed, irrevocably called for redemption (and an irrevocable deposit is made with a trustee in an amount at least equal to the outstanding principal amount of such indebtedness, the remaining scheduled payments of interest thereon to, but not including, such redemption date, and any premium) or otherwise satisfied or (B) that is secured by cash or Cash Equivalents irrevocably deposited with a trustee in an amount, in the case of this clause (B), at least equal to the outstanding principal amount of such indebtedness and the remaining scheduled payments of interest thereon and (2) includes, to the extent not otherwise included, any obligation by SNH or any Subsidiary to be liable for, or to pay, as obligor, guarantor or otherwise (other than for purposes of collection in the ordinary course of business), Debt of another Person (other than SNH or any Subsidiary) (it being understood that Debt shall be deemed to be incurred by SNH or any Subsidiary whenever SNH or such Subsidiary shall create, assume, guarantee or otherwise become liable in respect thereof).

        "Disqualified Stock" means, with respect to any Person, any Capital Stock of such Person which by the terms of such Capital Stock (or by the terms of any security into which it is convertible or for which it is exchangeable or exercisable), upon the happening of any event or otherwise, (1) matures or is mandatorily redeemable, pursuant to a sinking fund obligation or otherwise (other than Capital Stock which is redeemable solely in exchange for Capital Stock which is not Disqualified Stock or for Subordinated Debt), (2) is convertible into or exchangeable or exercisable for Debt, other than Subordinated Debt, or Disqualified Stock, or (3) is redeemable at the option of the holder thereof, in whole or in part (other than Capital Stock which is redeemable solely in exchange for Capital Stock which is not Disqualified Stock or for Subordinated Debt), in each case on or prior to the stated maturity of the principal of the notes.

        "Earnings from Operations" for any period means net earnings excluding gains and losses on sales of investments, gains or losses on early extinguishment of debt, extraordinary items and property valuation losses, in each case as reflected in the financial statements of SNH and its Subsidiaries for such period, determined on a consolidated basis in accordance with GAAP.

        "Encumbrance" means any mortgage, lien, charge, pledge, security interest or other encumbrance of any kind.

        "GAAP" means generally accepted accounting principles in the United States, which were in effect on December 20, 2001, which is the date on which securities were originally issued by SNH under the Indenture, dated as of December 20, 2001, between SNH and State Street Bank and Trust Company, as trustee.

        "Joint Venture Interests" means assets of SNH and its Subsidiaries constituting an equity investment in real estate assets or other properties, or in an entity holding real estate assets or other properties, jointly owned by SNH and its Subsidiaries, on the one hand, and one or more other Persons not constituting SNH's Affiliates, on the other hand, excluding any entity or properties (1) which is a

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Subsidiary or are properties if the co-ownership thereof (if in a separate entity) would constitute or would have constituted a Subsidiary or (2) to which, at the time of determination, SNH's manager at such time or an Affiliate of SNH's manager at such time provides management services. In no event shall Joint Venture Interests include equity securities that are part of a class of equity securities that are traded on a national or regional securities exchange or a recognized over-the-counter market or any investments in debt securities, mortgages or other Debt.

        "Make-Whole Amount" means, in connection with any optional redemption of any notes prior to August 15, 2027 the excess, if any, of (i) the aggregate present value as of the date of such redemption of each dollar of principal being redeemed and the amount of interest (exclusive of interest accrued to the date of redemption) that would have been payable in respect of such dollar if such redemption had been made on August 15, 2027 determined by discounting, on a semiannual basis, such principal and interest at the Reinvestment Rate (determined on the third Business Day preceding the date such notice of redemption is given) from the respective dates on which such principal and interest would have been payable if such redemption had been made on August 15, 2027 over (ii) the aggregate principal amount of the notes being redeemed. In the case of any redemption of the notes on or after August 15, 2027 the Make-Whole Amount equals zero.

        "Moody's" means Moody's Investors Service, Inc., or any successor thereof.

        "Person" means any individual, corporation, partnership, limited liability company, joint venture, association, joint-stock company, trust, unincorporated organization or government or any agency or political subdivision thereof.

        "Reinvestment Rate" means a rate per annum equal to the sum of 0.35% (thirty-five one hundredths of one percent) plus the yield on treasury securities at constant maturity under the heading "Week Ending" published in the Statistical Release under the caption "Treasury Constant Maturities" for the maturity (rounded to the nearest month) corresponding to the remaining life to maturity (which, in the case of maturities corresponding to the principal and interest due on the notes at their maturity, shall be deemed to be August 15, 2027), as of the payment date of the principal being redeemed. If no maturity exactly corresponds to such maturity, yields for the two published maturities most closely corresponding to such maturity shall be calculated pursuant to the immediately preceding sentence and the Reinvestment Rate shall be interpolated or extrapolated from such yields on a straight-line basis, rounding in each of such relevant periods to the nearest month. For purposes of calculating the Reinvestment Rate, the most recent Statistical Release published prior to the date of determination of the Make-Whole Amount shall be used.

        "Secured Debt" means Debt of SNH or its Subsidiaries secured by an Encumbrance on the property of SNH or its Subsidiaries.

        "Significant Subsidiary" means any Subsidiary which is a "significant subsidiary" (within the meaning of Regulation S-X, promulgated by the SEC under the Securities Act of 1933, as amended) of SNH.

        "Standard & Poor's" means Standard & Poor's Ratings Services, a Standard & Poor's Financial Services LLC business, or any successor thereof.

        "Statistical Release" means the statistical release designated "H.15(519)" or any successor publication which is published weekly by the Federal Reserve System and which establishes yields on actively traded United States government securities adjusted to constant maturities or, if such statistical release is not published at the time of any determination under the Indenture, then any publicly available source of similar market data which shall be designated by SNH.

        "Subordinated Debt" means Debt which by the terms of such Debt is subordinated in right of payment to the principal of and interest and premium, if any, on the notes.

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        "Subsidiary" means any corporation or other Person of which a majority of (1) the voting power of the voting equity securities or (2) the outstanding equity interests of which are owned, directly or indirectly, by SNH or one or more other Subsidiaries of SNH. For the purposes of this definition, "voting equity securities" means equity securities having voting power for the election of directors or persons serving comparable functions as directors, whether at all times or only so long as no senior class of security has such voting power by reason of any contingency.

        "Total Assets" as of any date means the sum of (1) the Undepreciated Real Estate Assets and (2) all other assets of SNH and its Subsidiaries determined in accordance with GAAP (but excluding accounts receivable and intangibles).

        "Total Unencumbered Assets" as of any date means the sum of (1) Undepreciated Real Estate Assets not securing any portion of Secured Debt and (2) the amount of all other assets of SNH and its Subsidiaries, not securing any portion of Secured Debt, in each case on such date determined on a consolidated basis in accordance with GAAP (but excluding accounts receivable and intangibles); provided that, in determining Total Unencumbered Assets as a percentage of the aggregate outstanding principal amount of the Unsecured Debt of SNH and its Subsidiaries on a consolidated basis for purposes of the covenant set forth above under "—Certain Covenants—Maintenance of Total Unencumbered Assets," Joint Venture Interests shall be excluded from Total Unencumbered Assets to the extent such Joint Venture Interests would otherwise be included therein.

        "Undepreciated Real Estate Assets" as of any date means the cost (original cost plus capital improvements) of real estate and associated tangible personal property used in connection with the real estate assets of SNH and its Subsidiaries on such date, before depreciation and amortization determined on a consolidated basis in accordance with GAAP.

        "Unsecured Debt" means any Debt of SNH or its Subsidiaries which is not Secured Debt.

Sinking Fund

        The notes are not entitled to any sinking fund payments.

The Registrar and Paying Agent

        We have initially designated U.S. Bank National Association as the registrar and paying agent for the notes. Payments of interest and principal will be made, and the notes will be transferable, at the office of the paying agent, or at such other place or places as may be designated pursuant to the Indenture. For notes which we issue in book-entry form evidenced by a global note, payments will be made to DTC.

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MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

        Tax legislation enacted in December 2017 made substantial changes to the Internal Revenue Code of 1986, as amended, or the IRC. Among those changes are a significant permanent reduction in the generally applicable corporate tax rate, changes in the taxation of individuals and other noncorporate taxpayers that generally reduce their taxes on a temporary basis subject to "sunset" provisions, and the elimination or modification of various deductions (including substantial limitation of the deduction for personal state and local taxes imposed on individuals and limitations on the deduction of business interest expense and net operating losses). While the effect of these and other changes made in this legislation is uncertain, and many of the provisions of the new law will require guidance through the issuance of Treasury regulations and other administrative pronouncements in order to assess their effect, we do not anticipate that the new legislation will materially impact our qualification and taxation as a REIT.

        The following summary of United States federal income tax considerations is based upon the IRC, Treasury regulations, and rulings and decisions now in effect, all of which are subject to change, possibly with retroactive effect, or possible differing interpretations. We have not sought a ruling from the Internal Revenue Service, or the IRS, with respect to any matter described in this summary, and we cannot provide any assurance that the IRS or a court will agree with the statements made in this summary. The summary applies to you only if you hold our notes as a capital asset, which is generally an asset held for investment rather than as inventory or as property used in a trade or business. The summary does not discuss all of the particular tax considerations that might be relevant to you if you are subject to special rules under federal income tax law, for example if you are:

•

a bank, insurance company or other financial institution;



•

a regulated investment company or REIT;



•

a subchapter S corporation;



•

a broker, dealer or trader in securities or foreign currency;



•

a U.S. holder (as defined below) that has a functional currency other than the United States dollar;



•

a person that acquires or owns our notes in connection with employment or other performance of services;



•

a person subject to alternative minimum tax;



•

a person that acquires or owns our notes as part of a straddle, hedging transaction, constructive sale transaction, constructive ownership transaction or conversion transaction, or as part of a "synthetic security" or other integrated financial transaction;



•

a United States expatriate;



•

a nonresident alien individual present in the United States for 183 days or more during an applicable taxable year;



•

a holder subject to special tax accounting rules as a result of their use of applicable financial statements (within the meaning of Section 451(b)(3) of the IRC); or



•

except as specifically described in the following summary, a trust, estate, tax-exempt entity or foreign person.

In addition, the following summary does not address all possible tax considerations relating to the acquisition, ownership and disposition of our notes, and in particular does not discuss any estate, gift, generation-skipping transfer, state, local or foreign tax considerations. For all these reasons, we

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encourage you and any prospective acquiror of our notes to consult with a tax advisor about the federal income tax and other tax considerations of the acquisition, ownership and disposition of our notes.

        Your federal income tax consequences generally will differ depending on whether or not you are a "U.S. holder." For purposes of this summary, you are a U.S. holder if you are a beneficial owner of our notes and for federal income tax purposes are:

•

an individual who is a citizen or resident of the United States, including an alien individual who is a lawful permanent resident of the United States or meets the substantial presence residency test under the federal income tax laws;



•

an entity treated as a corporation for federal income tax purposes that is created or organized in or under the laws of the United States, any state thereof or the District of Columbia;



•

an estate the income of which is subject to federal income taxation regardless of its source; or



•

a trust if a court within the United States is able to exercise primary supervision over the administration of the trust and one or more United States persons have the authority to control all substantial decisions of the trust, or, to the extent provided in Treasury regulations, a trust in existence on August 20, 1996 that has elected to be treated as a domestic trust;

whose status as a U.S. holder is not overridden by an applicable tax treaty. Conversely, you are a "non-U.S. holder" if you are a beneficial owner of our notes other than an entity (or other arrangement) treated as a partnership for federal income tax purposes or a U.S. holder. If any entity (or other arrangement) treated as a partnership for federal income tax purposes holds our notes, the tax treatment of a partner in the partnership generally will depend upon the status of the partner and the activities of the partnership. Any entity or other arrangement treated as a partnership for federal income tax purposes that holds our notes and the partners in such a partnership (as determined for federal income tax purposes) are urged to consult their own tax advisors about the federal income tax consequences and other tax consequences of the acquisition, ownership and disposition of our notes.

        It is expected that the notes will not be issued with original issue discount for United States federal income tax purposes, or OID. The notes will be treated as issued with OID if their principal amount exceeds their "issue price" (i.e., the first price at which a substantial amount of our notes is sold for money, not including sales to bond houses, brokers or similar persons or organizations acting in the capacity of underwriters, placement agents or wholesalers) by an amount greater than or equal to a de minimis amount (generally 0.25% of the principal amount of the note multiplied by the number of complete years from the issue date of the note to its maturity). If the notes are treated as issued with OID under these rules, a holder would generally be required to include OID in income based on a constant yield to maturity accrual method before the receipt of corresponding cash payments. The remainder of this discussion assumes that the notes will not be issued with OID for United States federal income tax purposes.

Tax Considerations for U.S. Holders

        If you are a U.S. holder:

        Payments of interest.    You must generally include interest on a note in your gross income as ordinary interest income:

•

when you receive it, if you use the cash method of accounting for federal income tax purposes, or



•

when it accrues, if you use the accrual method of accounting for federal income tax purposes.

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Any portion of the purchase price for a note that is allocable to prior accrued interest generally may be treated as offsetting a portion of the interest income from the next scheduled interest payment on the note. Any interest income so offset is not taxable.

        Market discount.    If you acquire a note and your adjusted tax basis in it upon acquisition is less than its principal amount, you will be treated as having acquired the note at a "market discount" unless the amount of this market discount is less than a de minimis amount (generally 0.25% of the principal amount of the note multiplied by the number of remaining whole years to maturity of the note). Under the market discount rules, you will be required to treat any gain on the sale, exchange, redemption, retirement, or other taxable disposition of a note, or any appreciation in a note in the case of certain nontaxable dispositions, such as a gift, as ordinary income to the extent of the market discount which has not previously been included in your income and which is treated as having accrued on the note at the time of the disposition. In addition, you may be required to defer, until the maturity of the note or earlier taxable disposition, the deduction of all or a portion of the interest expense on any indebtedness incurred or continued to purchase or carry the note. Any market discount will be considered to accrue ratably during the period from the date of your acquisition to the maturity date of the note, unless you elect to accrue the market discount on a constant yield method. In addition, you may elect to include market discount in income currently as it accrues, on either a ratable or constant yield method, in which case the rule described above regarding deferral of interest deductions will not apply. This election to include market discount in income currently, once made, applies to all market discount obligations acquired by you during or after the first taxable year to which the election applies and may not be revoked without the consent of the IRS. We encourage you to consult with your tax advisor regarding these elections.

        Amortizable bond premium.    If you acquire a note and your adjusted tax basis in it upon acquisition is greater than its principal amount, you will be treated as having acquired the note with "bond premium." You generally may elect to amortize this bond premium over the remaining term of the note on a constant yield method, and the amount amortized in any year will generally be treated as a reduction of your interest income from the note for that year. If the amount of your bond premium amortization would be lower if calculated based on an earlier optional redemption date and the redemption price on that date than the amount of amortization calculated through that date based on the note's maturity date and its stated principal amount, then you must calculate the amount and timing of your bond premium amortization deductions assuming that the note will be redeemed on the optional redemption date at the optional redemption price. You may generally recalculate your bond premium amortization amount and schedule of deductions to the extent your note is not actually redeemed at that earlier optional redemption date. If you do not make an election to amortize bond premium, your bond premium on a note will decrease the gain or increase the loss that you otherwise recognize on a disposition of that note. Any election to amortize bond premium applies to all taxable debt obligations that you hold at the beginning of the first taxable year to which the election applies and that you thereafter acquire. You may not revoke an election to amortize bond premium without the consent of the IRS. We encourage you to consult with your tax advisor regarding this election.

        Disposition of a note.    Upon the sale, exchange, redemption, retirement or other disposition of a note, you generally will recognize taxable gain or loss in an amount equal to the difference, if any, between (1) the amount you receive in cash, or in property valued at its fair market value, upon this sale, exchange, redemption, retirement or other disposition, other than amounts representing accrued and unpaid interest which will be taxable as described above under "Payments of interest," and (2) your adjusted tax basis in the note. Your adjusted tax basis in the note will, in general, equal your acquisition cost for the note, exclusive of any amount paid allocable to prior accrued interest, as increased by any market discount you have included in income in respect of the note, and as decreased by any amortized bond premium on the note. Except to the extent of any accrued market discount not previously included in income, as discussed above, your gain or loss will generally be capital gain or

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loss, and will be long-term capital gain or loss if you have held the note for more than one year at the time of disposition. For noncorporate U.S. holders, preferential rates of tax may apply to long-term capital gains. The deductibility of capital losses is subject to limitation.

        Medicare contribution tax.    U.S. holders that are individuals, estates or trusts are generally required to pay a 3.8% Medicare tax on their net investment income (including interest on our notes and gains from the sale or other disposition of our notes), or in the case of estates and trusts on their net investment income that is not distributed, in each case to the extent that their total adjusted income exceeds applicable thresholds.

Tax Considerations for Non-U.S. Holders

        The rules governing the United States federal income taxation of non-U.S. holders are complex, and the following discussion is intended only as a summary of material considerations of an investment in our notes relevant to such investors. If you are a non-U.S. holder, we urge you to consult with your own tax advisor to determine the impact of United States federal, state, local and foreign tax laws, including any tax return filing and other reporting requirements, with respect to your acquisition of or investment in our notes.

        If you are a non-U.S. holder:

        Generally.    You will not be subject to federal income taxes on payments of principal, premium, or Make-Whole Amount, if any, or interest on a note, or upon the sale, exchange, redemption, retirement or other disposition of a note, if:

•

you do not own directly or indirectly 10% or more of the total voting power of all classes of our voting shares;



•

your income and gain in respect of the note is not effectively connected with the conduct of a United States trade or business;



•

you are not a controlled foreign corporation that is related to or under common control with us;



•

we or the applicable paying agent, or the Withholding Agent, have timely received from you a properly executed, applicable IRS Form W-8 or substantially similar form in the year in which a payment of interest, principal, premium, or Make-Whole Amount occurs, or in a previous calendar year to the extent provided for in the instructions to the applicable IRS Form W-8; and



•

in the case of gain upon the sale, exchange, redemption, retirement or other disposition of a note recognized by an individual non-U.S. holder, you were present in the United States for less than 183 days during the taxable year in which the gain was recognized.

        The IRS Form W-8 or a substantially similar form must be signed by you under penalties of perjury certifying that you are a non-U.S. holder and providing your name and address, and you must inform the Withholding Agent of any change in the information on the statement within 30 days of the change. If you hold a note through a securities clearing organization or other qualified financial institution, the organization or institution may provide a signed statement to the Withholding Agent. However, in that case, the signed statement must generally be accompanied by a statement containing the relevant information from the executed IRS Form W-8 or substantially similar form that you provided to the organization or institution. If you are a partner in a partnership holding our notes, both you and the partnership must comply with applicable certification requirements.

        Except in the case of income or gain in respect of a note that is effectively connected with the conduct of a United States trade or business, discussed below, interest received or gain recognized by you which does not qualify for exemption from taxation will be subject to federal income tax at a rate of 30%, which will be withheld from payments of interest, unless reduced or eliminated by an

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applicable income tax treaty. You must generally use an applicable IRS Form W-8, or a substantially similar form, to claim income tax treaty benefits. If you are a non-U.S. holder claiming benefits under an income tax treaty, you should be aware that you may be required to obtain a taxpayer identification number and to certify your eligibility under the applicable treaty's limitations on benefits article in order to comply with the applicable certification requirements of the Treasury regulations.

        Effectively connected income and gain.    If you are a non-U.S. holder whose income and gain in respect of a note are effectively connected with the conduct of a United States trade or business (and, if provided by an applicable income tax treaty, are attributable to a permanent establishment or fixed base you maintain in the United States), you will be subject to regular federal income tax on this income and gain in generally the same manner as U.S. holders, and general federal income tax return filing requirements will apply. In addition, if you are a corporation, you may be subject to a branch profits tax equal to 30% of your effectively connected adjusted earnings and profits for the taxable year, unless you qualify for a lower rate under an applicable income tax treaty. To obtain an exemption from withholding on interest on the notes that is effectively connected with the conduct of a United States trade or business, you must generally supply to the Withholding Agent an applicable IRS Form W-8, or a substantially similar form.

Information Reporting, Backup Withholding, and Foreign Account Withholding

        Information reporting, backup withholding and withholding under the Foreign Account Tax Compliance Act, or FATCA, may apply to interest and other payments to you under the circumstances discussed below. Amounts withheld under backup withholding are generally not an additional tax and may be refunded by the IRS or credited against your federal income tax liability, provided that you furnish required information to the IRS.

        Under FATCA, non-U.S. financial institutions and other non-U.S. entities are subject to diligence and reporting requirements for purposes of identifying accounts and investments held directly or indirectly by U.S. persons. The failure to comply with these additional information reporting, certification and other requirements could result in a 30% withholding tax on applicable payments to non-U.S. persons, notwithstanding any otherwise applicable provisions of an income tax treaty. In particular, a payee that is a foreign financial institution that is subject to the diligence and reporting requirements described above must enter into an agreement with the U.S. Department of the Treasury requiring, among other things, that it undertake to identify accounts held by "specified United States persons" or "United States-owned foreign entities" (each as defined in the IRC), annually report information about such accounts, and withhold 30% on applicable payments to noncompliant foreign financial institutions and account holders. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States with respect to these requirements may be subject to different rules. The foregoing withholding will generally apply to payments of interest on our notes, and is expected to generally apply to other "withholdable payments" (including payments of gross proceeds from a sale, exchange, redemption, retirement, or other disposition of our notes) made after December 31, 2018. In general, to avoid withholding, any non-U.S. intermediary through which a holder owns our notes must establish its compliance with the foregoing regime, and a non-U.S. holder must provide specified documentation (usually an applicable IRS Form W-8) containing information about its identity, its status, and if required, its direct and indirect U.S. owners. We encourage you to consult with your tax advisor regarding foreign account tax compliance if you hold our notes through a non-U.S. intermediary or are a non-U.S. holder.

        If you are a U.S. holder.    You may be subject to backup withholding when you receive interest payments on a note or proceeds upon the sale, exchange, redemption, retirement or other disposition

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of a note. In general, you can avoid this backup withholding if you properly execute under penalties of perjury an IRS Form W-9 or a substantially similar form on which you:

•

provide your correct taxpayer identification number;



•

certify that you are exempt from backup withholding because (a) you come within an enumerated exempt category, (b) you have not been notified by the IRS that you are subject to backup withholding, or (c) you have been notified by the IRS that you are no longer subject to backup withholding; and



•

certify that you are a U.S. citizen or other U.S. person.

If you do not provide your correct taxpayer identification number and appropriate certifications on an IRS Form W-9 or a substantially similar form, you may be subject to penalties imposed by the IRS.

        Unless you have established on a properly executed IRS Form W-9 or a substantially similar form that you come within an enumerated exempt category, interest and other payments on the notes paid to you during the calendar year, and the amount of tax withheld, if any, will be reported to you and to the IRS.

        If you are a non-U.S. holder.    The amount of interest paid to you on a note during each calendar year, and the amount of tax withheld, if any, will generally be reported to you and to the IRS. This information reporting requirement applies regardless of whether you were subject to withholding on interest and other payments on our notes or whether the withholding was reduced or eliminated by an applicable tax treaty. Also, interest paid to you on a note generally will be subject to backup withholding unless you properly certify to the Withholding Agent your non-U.S. holder status on an applicable IRS Form W-8 or a substantially similar form in the manner described above, under "Tax Considerations for Non-U.S. Holders." Information reporting and backup withholding will not apply to proceeds you receive upon the sale, exchange, redemption, retirement or other disposition of a note, if you properly certify to the Withholding Agent that you are a non-U.S. holder on an applicable IRS Form W-8 or a substantially similar form. Even without having executed an applicable IRS Form W-8 or a substantially similar form, however, in some cases information reporting and backup withholding may not apply to proceeds you receive upon the sale, exchange, redemption, retirement or other disposition of a note, if you receive those proceeds through a broker's foreign office.

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UNDERWRITING (CONFLICTS OF INTEREST)

        We intend to offer the notes through the underwriters named below. BBVA Securities Inc., Mizuho Securities USA LLC, RBC Capital Markets, LLC, UBS Securities LLC and Wells Fargo Securities, LLC are acting as joint book-running managers of this offering and as representatives of the underwriters. Subject to the terms and conditions contained in an underwriting agreement between us and the underwriters, we have agreed to sell to the underwriters, and the underwriters have severally agreed to purchase from us, the aggregate principal amount of the notes listed opposite their names below.

        The underwriters have agreed to purchase all of the notes sold pursuant to the underwriting agreement if they purchase any of the notes. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the nondefaulting underwriters may be increased or the underwriting agreement may be terminated.

        We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended, or to contribute to payments the underwriters may be required to make in respect of those liabilities.

        The underwriters are offering the notes, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel, including the validity of the notes, and other conditions contained in the underwriting agreement, such as the receipt by the underwriters of officers' certificates and legal opinions. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Commissions, Discount and Expenses

        The representatives of the underwriters have advised us that the underwriters propose initially to offer the notes to the public at the public offering price listed on the cover page of this prospectus supplement and to dealers at that price less a concession not in excess of 0.400% of the principal amount per note. The underwriters may allow, and the dealers may reallow, a discount not in excess of

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0.250% of the principal amount per note to other dealers. After the initial public offering, the public offering price, concessions and discount may be changed.

        The following table summarizes the discount that we will pay to the underwriters in connection with this offering.

        The expenses of this offering, not including the underwriting discount, are estimated to be $750,000 and are payable by us.

New Issue of Securities

        The notes will be a new issue of securities with no established trading market. We do not intend to apply for listing of the notes on any securities exchange or for quotation of the notes on any automated dealer quotation system. We have been advised by the underwriters that they presently intend to make a market in the notes after completion of this offering. However, they are under no obligation to do so and may discontinue any market-making activities at any time without any notice. We cannot provide you with any assurance of the liquidity of the trading market for the notes or that an active public market will develop for the notes. If an active public trading market does not develop for the notes, the market price and liquidity of the notes may be adversely affected.

Price Stabilization and Short Positions

        In connection with this offering, the underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the notes. Specifically, the underwriters may over allot in connection with the offering of the notes, creating a syndicate short position. In addition, the underwriters may bid for, and purchase, the notes in the open market to cover short positions or to stabilize the price of the notes. Finally, the underwriters may reclaim selling concessions allowed for distributing the notes in this offering, if the underwriters repurchase previously distributed notes in transactions to cover short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of the notes above independent market levels. The underwriters are not required to engage in any of these activities at any time.

        Neither we nor any of the underwriters makes any representation or prediction as to the direction or magnitude of any effect that the transactions described in the preceding paragraph may have on the price of the notes. In addition, neither we nor any of the underwriters makes any representation that the underwriters will engage in those types of transactions or that those transactions, once commenced, will not be discontinued without notice.

Conflicts of Interest

        Affiliates of certain of the underwriters, including affiliates of BBVA Securities Inc., Mizuho Securities USA LLC, RBC Capital Markets, LLC, UBS Securities LLC and Wells Fargo Securities, LLC are lenders to us under our revolving credit facility and will receive pro rata portions of the net proceeds from this offering used to reduce amounts outstanding thereunder.

Other Relationships

        Some of the underwriters and their affiliates have engaged in, and may in the future engage in, investment banking and other commercial dealings in the ordinary course of business with us. They

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have received customary fees and commissions for these transactions. U.S. Bancorp Investments, Inc., one of the underwriters, is an affiliate of the trustee.

        In addition, in the ordinary course of their business activities, the underwriters and their affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. Certain of the underwriters or their affiliates that have a lending relationship with us routinely hedge their credit exposure to us consistent with their customary risk management policies. Typically, such underwriters and their affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities, including potentially the notes offered hereby. Any such credit default swaps or short positions could adversely affect future trading price of the notes offered hereby. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

        Each of Associated Investment Services, Inc., a Financial Industry Regulatory Authority member and subsidiary of Associated Banc-Corp, and First Hawaiian Bank is being paid a referral fee by Samuel A. Ramirez & Company, Inc.

Notice to Prospective Investors

        Each purchaser of our notes that is (1) an employee benefit plan subject to Title I of Employee Retirement Income Security Act of 1974, as amended, or ERISA, (2) a plan or account subject to Section 4975 of the IRC or (3) an entity deemed to hold "plan assets" of any such employee benefit plan, plan or account, by acceptance of our notes, will be deemed to have represented and warranted that a fiduciary acting on its behalf is causing it to purchase our notes and that such fiduciary:

(a)

is a U.S. bank, a U.S. insurance carrier, a registered investment adviser, a registered broker-dealer or an independent fiduciary that holds or has at least $50 million of assets under management or control, in each case as specified in 29 CFR Section 2510.3-21(c)(1)(i), but in any event excluding an IRA owner (or a relative of an IRA owner) if the purchaser is the IRA owner's own IRA;



(b)

is independent (for purposes of 29 CFR Section 2510.3-21(c)(1)) of us, each underwriter and their respective affiliates, collectively the Transaction Parties;



(c)

is capable of evaluating investment risks independently, both in general and with regard to particular transactions and investment strategies, including the purchaser's transactions with the Transaction Parties hereunder;



(d)

has been advised that none of the Transaction Parties has undertaken or will undertake to provide impartial investment advice, or has given or will give advice in a fiduciary capacity, in connection with the purchaser's transactions with the Transaction Parties contemplated hereby;



(e)

is a "fiduciary" under Section 3(21)(a) of ERISA or Section 4975(e)(3) of the IRC, or both, as applicable, with respect to, and is responsible for exercising independent judgment in evaluating, the purchaser's transactions with the Transaction Parties contemplated hereby; and



(f)

understands and acknowledges the existence and nature of the underwriting discounts, commissions and fees, and any other related fees, compensation arrangements or financial interests, as described in this prospectus supplement; and understands, acknowledges and agrees that no such fee or other compensation is a fee or other compensation for the provision of investment advice, and that none of the Transaction Parties, nor any of their

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respective directors, trustees, officers, members, partners, employees, principals or agents has received or will receive a fee or other compensation from the purchaser or such fiduciary for the provision of investment advice (rather than other services) in connection with the purchaser's transactions with the Transaction Parties contemplated hereby.

Notice to Prospective Investors in Canada

        The notes may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the notes must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

        Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser's province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser's province or territory for particulars of these rights or consult with a legal advisor.

        Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

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LEGAL MATTERS

        Sullivan & Worcester LLP, Boston, Massachusetts, our lawyers, will issue an opinion about the legality of the notes. Sidley Austin LLP, New York, New York, the underwriters' lawyers, will also issue an opinion to the underwriters as to certain matters. Sullivan & Worcester LLP and Sidley Austin LLP will rely, as to certain matters of Maryland law, upon an opinion of Venable LLP, Baltimore, Maryland. Sullivan & Worcester LLP also has passed upon our qualification and taxation as a REIT in an opinion filed as an exhibit to the registration statement of which this prospectus supplement and the accompanying prospectus are a part. Sullivan & Worcester LLP also represents RMR LLC, which is our manager, Five Star and certain of their affiliates and related parties on various matters.

EXPERTS

        Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements and schedule included in our Annual Report on Form 10-K for the year ended December 31, 2016, and the effectiveness of our internal control over financial reporting as of December 31, 2016, as set forth in their reports, which are incorporated by reference in this prospectus supplement and elsewhere in the registration statement. Our financial statements and schedule are incorporated by reference in reliance on Ernst & Young LLP's reports, given on their authority as experts in accounting and auditing.

        The combined statement of revenues and certain expenses of the CCIT—Healthcare Properties for the year ended December 31, 2014, incorporated in this prospectus supplement and the accompanying prospectus by reference from the Current Report on Form 8-K filed by us on June 26, 2015, have been audited by RSM US LLP (formerly McGladrey LLP), independent auditor, as stated in their report, which is incorporated in this prospectus supplement and the accompanying prospectus by reference. Such statement of revenues and certain expenses has been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

        The statement of revenues and certain expenses of the Senior Living Communities for the year ended December 31, 2014, incorporated in this prospectus supplement and the accompanying prospectus by reference from the Current Report on Form 8-K filed by us on June 26, 2015, have been audited by PricewaterhouseCoopers LLP, independent certified public accountants, as stated in their report, which is incorporated in this prospectus supplement and the accompanying prospectus by reference. Such statement of revenues and certain expenses has been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

        You may read and copy any material that we file with the SEC at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. You may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. You may also access our SEC filings over the internet at the SEC's website at http://www.sec.gov.

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        THE AMENDED AND RESTATED DECLARATION OF TRUST ESTABLISHING SENIOR HOUSING PROPERTIES TRUST, DATED SEPTEMBER 20, 1999, AS AMENDED AND SUPPLEMENTED, AS FILED WITH THE STATE DEPARTMENT OF ASSESSMENTS AND TAXATION OF MARYLAND, PROVIDES THAT NO TRUSTEE, OFFICER, SHAREHOLDER, EMPLOYEE OR AGENT OF SENIOR HOUSING PROPERTIES TRUST SHALL BE HELD TO ANY PERSONAL LIABILITY, JOINTLY OR SEVERALLY, FOR ANY OBLIGATION OF, OR CLAIM AGAINST, SENIOR HOUSING PROPERTIES TRUST. ALL PERSONS DEALING WITH SENIOR HOUSING PROPERTIES TRUST IN ANY WAY SHALL LOOK ONLY TO THE ASSETS OF SENIOR HOUSING PROPERTIES TRUST FOR THE PAYMENT OF ANY SUM OR THE PERFORMANCE OF ANY OBLIGATION.

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PROSPECTUS

SENIOR HOUSING PROPERTIES TRUST

Debt Securities, Common Shares of Beneficial Interest,
Preferred Shares of Beneficial Interest, Depositary Shares and Warrants

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        We or our selling security holders may offer, issue and sell, from time to time, in one or more offerings:

•

debt securities;



•

common shares of beneficial interest;



•

preferred shares of beneficial interest;



•

depositary shares; and



•

warrants.

        The securities described in this prospectus may be offered and sold separately or in any combination, and may include convertible or exchangeable securities.

        This prospectus describes some of the general terms that may apply to these securities. The specific amounts and terms of any securities to be offered, issued or sold, and the identity of any selling security holders, will be described in the applicable prospectus supplement. The applicable prospectus supplement may also add to, update or change information contained in this prospectus. You should carefully read this prospectus and any accompanying prospectus supplement as well as the documents incorporated by reference in such documents before you decide to invest in any of these securities.

        We or our selling security holders may offer and sell these securities to or through one or more underwriters, dealers and agents, or directly to purchasers, on a continuous or delayed basis. The prospectus supplement for each offering will describe the terms of the plan of distribution and set forth the names of any underwriters, dealers or agents involved in the sale of the securities. Unless otherwise set forth in the applicable prospectus supplement, we will not receive any proceeds from the sale of securities sold by any selling security holder.

        Our common shares of beneficial interest are listed on the New York Stock Exchange, or the NYSE, under the symbol "SNH." If any other securities offered by this prospectus will be listed on a securities exchange, such listing will be described in the applicable prospectus supplement.

        Investment in our securities involves risk, including those described under "Risk Factors" beginning on page 1 of this prospectus. You should carefully read and consider these risk factors and the risk factors included in the reports that we file under the Securities Exchange Act of 1934, as amended, in any prospectus supplement relating to specific offerings of securities and in other documents that we file with the Securities and Exchange Commission.

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is June 26, 2015.

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ABOUT THIS PROSPECTUS

        References in this prospectus to "we," "us," "our" or "SNH" mean Senior Housing Properties Trust and its consolidated subsidiaries, unless the context otherwise requires.

        This prospectus is part of an "automatic shelf" registration statement that we filed with the Securities and Exchange Commission, or the SEC, as a "well-known seasoned issuer" as defined in Rule 405 under the Securities Act of 1933, as amended, or the Securities Act. Under this shelf registration process, we or our selling security holders may, from time to time, offer, issue and sell any of the securities or any combination of the securities described in this prospectus in such amounts and on such terms as set forth in a prospectus supplement in one or more offerings.

        This prospectus provides you with a general description of the securities that may be offered, which is not meant to be a complete description of each security. Each time we offer, issue or sell securities hereunder, or any selling security holder offers or sells securities hereunder, we or such selling security holder, as applicable, will provide a prospectus supplement that contains specific information about the amounts and terms of that offering. The prospectus supplement may also add to, update or change information contained in this prospectus. You should read both this prospectus and any prospectus supplement together with additional information described under the headings "Where You Can Find More Information" and "Information Incorporated By Reference." If there is any inconsistency between the information in this prospectus and any applicable prospectus supplement, you should rely on the information in the applicable prospectus supplement.

        You should rely only on the information provided or incorporated by reference in this prospectus or any relevant prospectus supplement. We have not authorized anyone to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. Neither we nor any selling security holder will make an offer of the securities in any jurisdiction where it is unlawful. You should assume that the information in this prospectus and any relevant prospectus supplement, as well as the information in any document incorporated or deemed to be incorporated into this prospectus and any relevant prospectus supplement is accurate only as of the date of the documents containing the information.

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PROSPECTUS SUMMARY

        We are a real estate investment trust, or REIT, organized under Maryland law, which invests in senior living communities, including independent living communities, assisted living communities and nursing homes, wellness centers and properties leased to medical providers, medical related businesses, clinics and biotech laboratory tenants. As of March 31, 2015, we owned 392 properties (419 buildings) located in 39 states and Washington, D.C., including four properties (seven buildings) classified as held for sale. On that date, the undepreciated carrying value of our properties, net of impairment losses, was $6.7 billion, excluding four properties (seven buildings) classified as held for sale.

        Our principal executive offices are located at Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458-1634, and our telephone number is (617) 796-8350. Our website is www.snhreit.com. The content of our website, and any information that is linked to our website (other than our filings with the SEC that are expressly incorporated by reference, as set forth under "Information Incorporated by Reference"), is not incorporated by reference in this prospectus, and you should not consider it a part of this prospectus.

RISK FACTORS

        Investing in our securities involves risks. You should carefully review the risk factors contained under the heading "Risk Factors" in our Annual Report on Form 10-K for the fiscal year ended December 31, 2014, or our Annual Report, and any risk factors that we may describe in our Quarterly Reports on Form 10-Q or Current Reports on Form 8-K filed subsequently to our Annual Report, which risk factors are incorporated by reference in this prospectus, the information contained under the heading "Warning Concerning Forward Looking Statements" in this prospectus or under any similar heading in any applicable prospectus supplement or in any document incorporated herein or therein by reference, any specific risk factors discussed under the caption "Risk Factors" in any applicable prospectus supplement or in any document incorporated herein or therein by reference and the other information contained in, or incorporated by reference in, this prospectus or any applicable prospectus supplement before making an investment decision. If any such risks occur, our business, financial condition or results of operations could be materially harmed, the market price of our securities could decline and you could lose all or part of your investment.

WARNING CONCERNING FORWARD LOOKING STATEMENTS

        THIS PROSPECTUS, INCLUDING THE DOCUMENTS THAT ARE INCORPORATED BY REFERENCE, CONTAINS STATEMENTS THAT CONSTITUTE FORWARD LOOKING STATEMENTS WITHIN THE MEANING OF THE PRIVATE SECURITIES LITIGATION REFORM ACT OF 1995 AND OTHER SECURITIES LAWS. ALSO, WHENEVER WE USE WORDS SUCH AS "BELIEVE," "EXPECT," "ANTICIPATE," "INTEND," "PLAN," "ESTIMATE" OR SIMILAR EXPRESSIONS, WE ARE MAKING FORWARD LOOKING STATEMENTS. THESE FORWARD LOOKING STATEMENTS ARE BASED UPON OUR PRESENT INTENT, BELIEFS OR EXPECTATIONS, BUT FORWARD LOOKING STATEMENTS ARE NOT GUARANTEED TO OCCUR AND MAY NOT OCCUR. FORWARD LOOKING STATEMENTS RELATE TO VARIOUS ASPECTS OF OUR BUSINESS, INCLUDING:

•

OUR ACQUISITIONS AND SALES OF PROPERTIES,



•

OUR ABILITY TO COMPETE FOR ACQUISITIONS AND TENANCIES EFFECTIVELY,



•

OUR ABILITY TO RAISE EQUITY OR DEBT CAPITAL,



•

OUR ABILITY TO PAY DISTRIBUTIONS TO OUR SHAREHOLDERS AND THE AMOUNT OF SUCH DISTRIBUTIONS,

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•

OUR ABILITY TO RETAIN OUR EXISTING TENANTS, ATTRACT NEW TENANTS AND MAINTAIN OR INCREASE CURRENT RENTAL RATES,



•

THE CREDIT QUALITIES OF OUR TENANTS,



•

OUR POLICIES AND PLANS REGARDING INVESTMENTS AND FINANCINGS,



•

THE FUTURE AVAILABILITY OF BORROWINGS UNDER OUR REVOLVING CREDIT FACILITY,



•

OUR ABILITY TO PAY INTEREST ON AND PRINCIPAL OF OUR DEBT,



•

OUR TAX STATUS AS A REIT,



•

OUR BELIEF THAT FIVE STAR QUALITY CARE, INC., OR FIVE STAR, OUR FORMER SUBSIDIARY, WHICH IS OUR LARGEST TENANT AND WHICH MANAGES CERTAIN OF OUR SENIOR LIVING COMMUNITIES FOR OUR ACCOUNT, HAS ADEQUATE FINANCIAL RESOURCES AND LIQUIDITY TO MEET ITS OBLIGATIONS TO US AND TO MANAGE OUR SENIOR LIVING COMMUNITIES SUCCESSFULLY, AND



•

OTHER MATTERS.

        OUR ACTUAL RESULTS MAY DIFFER MATERIALLY FROM THOSE CONTAINED IN OR IMPLIED BY OUR FORWARD LOOKING STATEMENTS AS A RESULT OF VARIOUS FACTORS. FACTORS THAT COULD HAVE A MATERIAL ADVERSE EFFECT ON OUR FORWARD LOOKING STATEMENTS AND UPON OUR BUSINESS, RESULTS OF OPERATIONS, FINANCIAL CONDITION, FUNDS FROM OPERATIONS, NORMALIZED FUNDS FROM OPERATIONS, NET OPERATING INCOME, CASH BASIS NET OPERATING INCOME, CASH FLOWS, LIQUIDITY AND PROSPECTS INCLUDE, BUT ARE NOT LIMITED TO:

•

THE IMPACT OF CHANGES IN THE ECONOMY AND THE CAPITAL MARKETS ON US AND OUR TENANTS AND MANAGERS,



•

THE IMPACT OF THE PATIENT PROTECTION AND AFFORDABLE CARE ACT, AS AMENDED BY THE HEALTH CARE AND EDUCATION RECONCILIATION ACT, OR COLLECTIVELY, THE ACA, AND OTHER EXISTING OR PROPOSED LEGISLATION OR REGULATIONS ON US, ON OUR TENANTS AND MANAGERS AND ON THEIR ABILITY TO PAY OUR RENTS AND RETURNS,



•

ACTUAL AND POTENTIAL CONFLICTS OF INTEREST WITH OUR MANAGING TRUSTEES, FIVE STAR, REIT MANAGEMENT & RESEARCH LLC, OR RMR LLC, REIT MANAGEMENT & RESEARCH INC., OR RMR INC, AFFILIATES INSURANCE COMPANY, OR AIC, D&R YONKERS LLC, SELECT INCOME REIT, OR SIR, AND THEIR RELATED PERSONS AND ENTITIES,



•

COMPLIANCE WITH, AND CHANGES TO, FEDERAL, STATE AND LOCAL LAWS AND REGULATIONS, ACCOUNTING RULES, TAX LAWS AND SIMILAR MATTERS,



•

LIMITATIONS IMPOSED ON OUR BUSINESS AND OUR ABILITY TO SATISFY COMPLEX RULES IN ORDER FOR US TO QUALIFY AS A REIT FOR U.S. FEDERAL INCOME TAX PURPOSES,



•

COMPETITION WITHIN THE HEALTHCARE AND REAL ESTATE INDUSTRIES, AND



•

ACTS OF TERRORISM, OUTBREAKS OF SO CALLED PANDEMICS OR OTHER MANMADE OR NATURAL DISASTERS BEYOND OUR CONTROL.

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FOR EXAMPLE:

•

FIVE STAR IS OUR LARGEST TENANT AND MANAGES CERTAIN OF OUR SENIOR LIVING COMMUNITIES FOR OUR ACCOUNT AND FIVE STAR MAY EXPERIENCE FINANCIAL DIFFICULTIES AS A RESULT OF A NUMBER OF FACTORS, INCLUDING, BUT NOT LIMITED TO:



•

MATERIAL WEAKNESSES IN ITS INTERNAL CONTROLS,



•

CHANGES IN MEDICARE AND MEDICAID PAYMENTS, INCLUDING THOSE THAT MAY RESULT FROM THE ACA AND EXISTING OR PROPOSED LEGISLATION OR REGULATIONS, WHICH COULD RESULT IN REDUCED RATES OR A FAILURE OF SUCH RATES TO COVER FIVE STAR'S COSTS,



•

CHANGES IN REGULATIONS AFFECTING FIVE STAR'S OPERATIONS,



•

CHANGES IN THE ECONOMY GENERALLY OR GOVERNMENTAL POLICIES WHICH REDUCE THE DEMAND FOR THE SERVICES FIVE STAR OFFERS,



•

INCREASES IN INSURANCE AND TORT LIABILITY AND OTHER COSTS,



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INEFFECTIVE INTEGRATION OF NEW ACQUISITIONS AND LEASED AND MANAGED COMMUNITIES, AND



•

INSUFFICIENT ACCESS TO CAPITAL AND FINANCING,



•

IF FIVE STAR'S OPERATIONS BECOME UNPROFITABLE, FIVE STAR MAY BECOME UNABLE TO PAY OUR RENTS AND WE MAY NOT RECEIVE OUR EXPECTED RETURN ON OUR INVESTED CAPITAL OR ADDITIONAL AMOUNTS FROM OUR SENIOR LIVING COMMUNITIES THAT ARE MANAGED BY FIVE STAR,



•

OUR ABILITY TO MAKE FUTURE DISTRIBUTIONS AND TO MAKE PAYMENTS OF PRINCIPAL AND INTEREST ON OUR NOTES OR OUR OTHER INDEBTEDNESS DEPENDS UPON A NUMBER OF FACTORS, INCLUDING OUR FUTURE EARNINGS, THE CAPITAL COSTS WE INCUR TO LEASE AND OPERATE OUR PROPERTIES AND OUR WORKING CAPITAL REQUIREMENTS. WE MAY BE UNABLE TO PAY OUR DEBT OBLIGATIONS OR TO MAINTAIN OUR CURRENT RATE OF DISTRIBUTIONS ON OUR COMMON SHARES AND FUTURE DISTRIBUTIONS MAY BE REDUCED OR ELIMINATED,



•

OUR ABILITY TO GROW OUR BUSINESS AND INCREASE OUR DISTRIBUTIONS DEPENDS IN LARGE PART UPON OUR ABILITY TO BUY PROPERTIES AND ARRANGE FOR THEIR PROFITABLE OPERATION OR LEASE THEM FOR RENTS, LESS PROPERTY OPERATING EXPENSES, THAT EXCEED OUR CAPITAL COSTS. WE MAY BE UNABLE TO IDENTIFY PROPERTIES THAT WE WANT TO ACQUIRE OR TO NEGOTIATE ACCEPTABLE PURCHASE PRICES, ACQUISITION FINANCING, MANAGEMENT CONTRACTS OR LEASE TERMS FOR NEW PROPERTIES,



•

OUR TENANTS MAY EXPERIENCE LOSSES AND BECOME UNABLE TO PAY OUR RENTS,



•

CONTINUED AVAILABILITY OF BORROWINGS UNDER OUR REVOLVING CREDIT FACILITY IS SUBJECT TO OUR SATISFYING CERTAIN FINANCIAL COVENANTS AND MEETING OTHER CUSTOMARY CREDIT FACILITY CONDITIONS THAT WE MAY BE UNABLE TO SATISFY,

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•

ACTUAL COSTS UNDER OUR REVOLVING CREDIT FACILITY OR OTHER FLOATING RATE CREDIT FACILITIES WILL BE HIGHER THAN LIBOR PLUS A PREMIUM BECAUSE OF OTHER FEES AND EXPENSES ASSOCIATED WITH SUCH FACILITIES,



•

THE MAXIMUM BORROWING AVAILABILITY UNDER OUR REVOLVING CREDIT FACILITY AND TERM LOAN MAY BE INCREASED TO UP TO $2.2 BILLION ON A COMBINED BASIS IN CERTAIN CIRCUMSTANCES. HOWEVER, INCREASING THE MAXIMUM BORROWING AVAILABILITY UNDER OUR REVOLVING CREDIT FACILITY AND TERM LOAN IS SUBJECT TO OUR OBTAINING ADDITIONAL COMMITMENTS FROM LENDERS, WHICH MAY NOT OCCUR,



•

WE HAVE THE OPTION TO EXTEND THE MATURITY DATE OF OUR REVOLVING CREDIT FACILITY UPON PAYMENT OF A FEE AND MEETING CERTAIN OTHER CONDITIONS. HOWEVER, THE APPLICABLE CONDITIONS MAY NOT BE MET,



•

THE MARGINS USED TO DETERMINE THE INTEREST RATE PAYABLE ON OUR REVOLVING CREDIT FACILITY AND TERM LOAN AND THE FACILITY FEE PAYABLE ON OUR REVOLVING CREDIT FACILITY ARE BASED ON OUR CREDIT RATINGS. FUTURE CHANGES IN OUR CREDIT RATINGS MAY CAUSE THE INTEREST AND FEES WE PAY TO CHANGE,



•

CONTINGENCIES IN OUR ACQUISITION AND SALE AGREEMENTS MAY NOT BE SATISFIED AND OUR PENDING SALES OR ACQUISITIONS AND ANY RELATED MANAGEMENT AGREEMENTS MAY NOT OCCUR, MAY BE DELAYED OR THE TERMS OF SUCH TRANSACTIONS MAY CHANGE,



•

WE MAY BE UNABLE TO REPAY OUR DEBT OBLIGATIONS WHEN THEY BECOME DUE,



•

SOME OF OUR TENANTS MAY NOT RENEW EXPIRING LEASES, AND WE MAY BE UNABLE TO LOCATE NEW TENANTS TO MAINTAIN OR INCREASE THE HISTORICAL OCCUPANCY RATES OF, OR RENTS FROM, OUR PROPERTIES,



•

RENTS THAT WE CAN CHARGE AT OUR PROPERTIES MAY DECLINE BECAUSE OF CHANGING MARKET CONDITIONS OR OTHERWISE, AND



•

WE BELIEVE THAT OUR RELATIONSHIPS WITH OUR RELATED PARTIES, INCLUDING FIVE STAR, RMR LLC, RMR INC, AIC, D&R YONKERS LLC, SIR AND OTHERS AFFILIATED WITH THEM MAY BENEFIT US AND PROVIDE US WITH COMPETITIVE ADVANTAGES IN OPERATING AND GROWING OUR BUSINESS. IN FACT, THE ADVANTAGES WE BELIEVE WE MAY REALIZE FROM THESE RELATIONSHIPS MAY NOT MATERIALIZE.

        THESE RESULTS COULD OCCUR DUE TO MANY DIFFERENT CIRCUMSTANCES, SOME OF WHICH ARE BEYOND OUR CONTROL, SUCH AS CHANGED MEDICARE AND MEDICAID RATES, NEW LEGISLATION OR REGULATIONS AFFECTING OUR BUSINESS OR THE BUSINESSES OF OUR TENANTS OR MANAGERS, CHANGES IN OUR TENANTS' OR MANAGERS' REVENUES OR COSTS, CHANGES IN OUR TENANTS' OR MANAGERS' FINANCIAL CONDITIONS, ACTS OF TERRORISM, NATURAL DISASTERS OR CHANGES IN CAPITAL MARKETS OR THE ECONOMY GENERALLY.

        THE INFORMATION CONTAINED ELSEWHERE IN THIS PROSPECTUS, AND IN OUR FILINGS WITH THE SEC, INCLUDING UNDER THE CAPTION "RISK FACTORS" IN OUR ANNUAL REPORT OR INCORPORATED HEREIN OR THEREIN, IDENTIFIES OTHER IMPORTANT FACTORS THAT COULD CAUSE DIFFERENCES FROM OUR FORWARD LOOKING STATEMENTS. OUR FILINGS WITH THE SEC ARE AVAILABLE ON THE SEC'S WEBSITE AT WWW.SEC.GOV.

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        YOU SHOULD NOT PLACE UNDUE RELIANCE UPON OUR FORWARD LOOKING STATEMENTS.

        EXCEPT AS REQUIRED BY LAW, WE DO NOT INTEND TO UPDATE OR CHANGE ANY FORWARD LOOKING STATEMENTS AS A RESULT OF NEW INFORMATION, FUTURE EVENTS OR OTHERWISE.

STATEMENT CONCERNING LIMITED LIABILITY

        THE AMENDED AND RESTATED DECLARATION OF TRUST ESTABLISHING SENIOR HOUSING PROPERTIES TRUST, DATED SEPTEMBER 20, 1999, AS AMENDED AND SUPPLEMENTED, AS FILED WITH THE STATE DEPARTMENT OF ASSESSMENTS AND TAXATION OF MARYLAND, PROVIDES THAT NO TRUSTEE, OFFICER, SHAREHOLDER, EMPLOYEE OR AGENT OF SENIOR HOUSING PROPERTIES TRUST SHALL BE HELD TO ANY PERSONAL LIABILITY, JOINTLY OR SEVERALLY, FOR ANY OBLIGATION OF, OR CLAIM AGAINST, SENIOR HOUSING PROPERTIES TRUST. ALL PERSONS DEALING WITH SENIOR HOUSING PROPERTIES TRUST IN ANY WAY SHALL LOOK ONLY TO THE ASSETS OF SENIOR HOUSING PROPERTIES TRUST FOR THE PAYMENT OF ANY SUM OR THE PERFORMANCE OF ANY OBLIGATION.

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RATIO OF EARNINGS TO FIXED CHARGES

        The following table sets forth our ratio of earnings to fixed charges for each of the periods shown.

        For purposes of calculating the ratios above, earnings have been calculated by adding fixed charges to income from continuing operations (including gains on sales of properties, if any) before income tax expense and equity in earnings (losses) of an investee. Fixed charges consist of interest expense (including net amortization of debt discounts, premiums and deferred financing fees). The ratios of earnings to fixed charges were computed by dividing our earnings by fixed charges. We did not have any preferred securities outstanding during any of the periods presented above, and therefore our ratio of earnings to combined fixed charges and preferred share distributions is the same as the ratio of earnings to fixed charges for each of the periods presented above.

USE OF PROCEEDS

        Unless otherwise described in a prospectus supplement, we intend to use the net proceeds that we receive from the sale of any securities covered by this prospectus for general business purposes, which may include acquiring and investing in additional properties and the repayment of borrowings under our revolving credit facility or other debt. Until we apply the proceeds from a sale of securities covered by this prospectus to their stated purposes, we may invest those proceeds in short term investments, including repurchase agreements, some or all of which may not be investment grade.

        Unless otherwise set forth in the applicable prospectus supplement, we will not receive any of the proceeds of the sale by any selling security holder of securities covered by this prospectus.

DESCRIPTION OF DEBT SECURITIES

        References in this "Description of Debt Securities" section to "we," "us," "our" or "SNH" mean Senior Housing Properties Trust and not any of its consolidated subsidiaries, unless the context otherwise requires. The following is a summary of some general terms and provisions of debt securities that we may offer by this prospectus. Because it is a summary, it does not contain all of the information that may be important to you. If you want more information, you should read the forms of indentures which we have filed as exhibits to the registration statement of which this prospectus is a part. If we issue debt securities, we will file any final indentures, and any supplemental indentures or officer's certificates related to the particular series of debt securities issued, with the SEC, and you should read those documents for further information about the terms and provisions of such debt securities. See "Where You Can Find More Information." This summary is also subject to and qualified by reference to the descriptions of the particular terms of our debt securities to be described in the applicable prospectus supplement. The applicable prospectus supplement may add to, update or change the terms of such debt securities from those described below.

        The debt securities sold under this prospectus will be direct obligations of SNH and, unless otherwise stated in a prospectus supplement, will not be obligations of any of its subsidiaries. Such debt obligations may be secured or unsecured, and may be senior or subordinated indebtedness. Our debt securities will be issued under one or more indentures between us and a trustee. Any indenture will be subject to and governed by the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act. The statements made in this prospectus relating to any indentures and the debt securities to be issued under the indentures are summaries of certain anticipated provisions of the indentures and are not complete.

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General

        We may issue debt securities that rank "senior," "senior subordinated" or "junior subordinated," and which may be convertible into another security. The debt securities that we refer to as "senior" will be direct obligations of SNH and will rank equally and ratably in right of payment with our other indebtedness that is not subordinated, without giving effect to collateral arrangements. We may issue debt securities that will be subordinated in right of payment to the prior payment in full of our senior debt, as defined in the applicable prospectus supplement, and may rank equally and ratably with our other senior subordinated indebtedness, if any, without giving effect to collateral arrangements. We refer to these as "senior subordinated" securities. We may also issue debt securities that may be subordinated in right of payment to the senior subordinated securities. These would be "junior subordinated" securities. We have filed with the registration statement, of which this prospectus is a part, three separate forms of indenture, one for the senior securities, one for the senior subordinated securities and one for the junior subordinated securities.

        We may issue debt securities without limit as to aggregate principal amount, in one or more series, in each case as we establish in one or more supplemental indentures. We need not issue all debt securities of one series at the same time. Unless we otherwise provide, we may reopen a series, without the consent of the holders of the series, for issuances of additional securities of that series.

        We anticipate that any indenture will provide that we may, but need not, designate more than one trustee under an indenture, each with respect to one or more series of debt securities. Any trustee under any indenture may resign or be removed with respect to one or more series of debt securities, and we may appoint a successor trustee to act with respect to any such series.

        The applicable prospectus supplement will describe the specific terms relating to the series of debt securities we will offer, including, where applicable, the following:

•

the title and series designation and whether they are senior securities, senior subordinated securities or junior subordinated securities;



•

the aggregate principal amount of the debt securities offered and any limit on the aggregate principal amount of that series that may be authenticated and delivered;



•

the percentage of the principal amount at which we will issue the debt securities and, if other than the principal amount of the debt securities, the portion of the principal amount of the debt securities payable upon maturity of the debt securities;



•

if convertible, the initial conversion price, the conversion period and any other terms governing such conversion;



•

the stated maturity date;



•

any fixed or variable interest rate or rates per annum;



•

whether such interest will be payable in cash or additional debt securities of the same series or will accrue and increase the aggregate principal amount outstanding of such series;



•

the place where principal, premium, if any, and interest will be payable and where the debt securities can be surrendered for transfer, exchange or conversion;



•

the date from which interest may accrue and any interest payment dates and any related record dates;



•

any sinking fund requirements;



•

any provisions for redemption or repurchase, including the redemption or repurchase price;

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•

whether the debt securities are denominated or payable in U.S. dollars, a foreign currency or units of two or more currencies;



•

whether the amount of payments of principal of or premium, if any, or interest on the debt securities may be determined with reference to an index, formula or other method and the manner in which such amounts shall be determined;



•

the events of default and covenants of the debt securities, to the extent different from or in addition to those described in this prospectus;



•

whether we will issue the debt securities in certificated or book-entry form;



•

whether the debt securities will be in registered or bearer form and, if in registered form, the denominations, if other than $2,000 and integral multiples of $1,000 in excess thereof, or, if in bearer form, the denominations and terms and conditions relating thereto;



•

whether we will issue any of the debt securities in permanent global form and, if so, the terms and conditions, if any, upon which interests in the global security may be exchanged, in whole or in part, for the individual debt securities represented by the global security;



•

any addition or change to the provisions relating to the defeasance or covenant defeasance provisions of, or the satisfaction and discharge of, the debt securities;



•

whether we will pay additional amounts on the debt securities in respect of any tax, assessment or governmental charge and, if so, whether we will have the option to redeem the debt securities instead of making this payment;



•

the subordination provisions, if any, relating to the debt securities;



•

if the debt securities are to be issued upon the exercise of warrants, the time, manner and place for such debt securities to be authenticated and delivered;



•

any restriction or condition on the transferability of debt securities;



•

any addition or change to the provisions related to compensation and reimbursement of the trustee which applies to the debt securities;



•

any addition or change to the provisions related to supplemental indentures both with and without the consent of the holders;



•

provisions, if any, granting special rights to holders upon the occurrence of specified events;



•

any addition or change to the events of default which applies to any debt securities and any change in the right of the trustee or the requisite holders of such debt securities to declare the principal amount thereof due and payable pursuant to the indenture;



•

any addition or change to the covenants set forth in the indenture, or described in this prospectus or any prospectus supplement, with respect to such series of debt securities; and



•

any other terms of debt securities of such series (which terms will not be inconsistent with the provisions of the Trust Indenture Act, but may modify, amend, supplement or delete any of the terms of the indenture, including those described in this prospectus or any prospectus supplement, with respect to such series).

        We will describe in the applicable prospectus supplement any material U.S. federal income tax considerations applicable to the debt securities offered by such prospectus supplement.

        We may issue debt securities at less than the principal amount payable at maturity. We refer to these securities as "original issue discount" securities. If material or applicable, we will describe in the

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applicable prospectus supplement special U.S. federal income tax considerations applicable to original issue discount securities.

        Except as may be described in any prospectus supplement, an indenture will not contain any other provisions that would limit our ability to incur indebtedness or that would afford holders of the debt securities protection in the event of a highly leveraged or similar transaction involving us or in the event of a change in control. You should review carefully the applicable prospectus supplement for information with respect to events of default and covenants applicable to the debt securities being offered.

Denominations, Interest, Registration and Transfer

        Unless otherwise described in the applicable prospectus supplement, we will issue debt securities of any series that are registered securities in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof, other than global securities which may be of any denomination.

        Unless otherwise specified in the applicable prospectus supplement, we will pay the interest, principal and any premium at the corporate trust office of the trustee or, at our option, we may make payment of interest by check mailed to the address of the person entitled to the payment as it appears in the applicable register or by wire transfer of funds to that person at an account maintained within the United States or, in the case of global securities, in accordance with the procedures of the depositary for such securities.

        If we do not punctually pay or otherwise provide for interest on any interest payment date, the defaulted interest will be paid either:

•

to the person in whose name the debt security is registered at the close of business on a special record date the trustee will fix; or



•

in any other lawful manner, all as the applicable indenture describes.

        You may have your debt securities divided into more debt securities of smaller authorized denominations or combined into fewer debt securities of larger authorized denominations, as long as the total principal amount is not changed. We call this an "exchange."

        You may exchange or transfer debt securities at the office of the applicable trustee. The trustee acts as our agent for registering debt securities in the names of holders and transferring debt securities. We may change this appointment to another entity or perform this role ourselves. The entity performing the role of maintaining the list of registered holders is called the "registrar." The registrar will also perform transfers.

        You will not be required to pay a service charge to transfer or exchange debt securities, but you may be required to pay for any tax or other governmental charge associated with the exchange or transfer. The registrar will make the transfer or exchange only if it is satisfied with your proof of ownership.

Merger, Consolidation or Sale of Assets

        We may not consolidate with or merge into any other person or convey, transfer or lease all or substantially all of our properties and assets to any other person (other than one of our direct or indirect wholly owned subsidiaries), and we may not permit any other person (other than one of our direct or indirect wholly owned subsidiaries) to consolidate with or merge into us, unless:

•

we are the surviving entity or, in case we consolidate with or merge into another person, the person formed by such consolidation or merger is, or in case we convey, transfer or lease all or substantially all of our properties and assets to any person, such acquiring person is, an entity organized and validly existing under the laws of the United States of America, any state thereof

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or the District of Columbia and expressly assumes, by a supplemental indenture executed and delivered to the trustee, in form satisfactory to the trustee, the due and punctual payment of the principal of and any premium and interest on all applicable debt securities issued under the applicable indenture and the performance or observance of every covenant of the applicable indenture on our part to be performed or observed;

•

immediately after giving effect to such transaction, and treating any indebtedness which becomes an obligation of us or any of our subsidiaries as a result of such transaction as having been incurred by us or such subsidiary at the time of such transaction, no event of default, and no event which, after notice or lapse of time or both, would become an event of default, in each case under the applicable indenture, has happened and is continuing; and



•

we have delivered to the trustee an officer's certificate and an opinion of counsel, each stating that such consolidation, merger, conveyance, transfer or lease and, if a supplemental indenture is required in connection with such transaction, such supplemental indenture comply with the applicable indenture provisions described in this paragraph and that all conditions precedent provided for in the applicable indenture relating to such transaction have been complied with.

Events of Default and Related Matters

        Events of Default.    The term "event of default" for any series of debt securities means any of the following:

•

we do not pay the principal of or any premium on a debt security of that series when due;



•

we do not pay interest on a debt security of that series within 30 days after its due date;



•

we do not deposit any sinking fund payment for that series within 30 days after its due date;



•

we remain in breach of any other covenant of the applicable indenture (other than a covenant added to the indenture solely for the benefit of another series) for 60 days after we receive a notice of default specifying the breach and requiring that it be remedied. Only the trustee or holders of at least a majority in principal amount of outstanding debt securities of the affected series may send the notice;



•

we experience specified events of bankruptcy, insolvency or reorganization; or



•

any other event of default described in the applicable prospectus supplement occurs.

        Remedies if an Event of Default Occurs.    If an event of default has occurred and has not been cured, the trustee or the holders of not less than a majority in principal amount of the outstanding debt securities of the affected series may declare the entire principal amount of all the debt securities of that series to be due and payable immediately. If an event of default occurs because we experience specified events of bankruptcy, insolvency or reorganization, the principal amount of all the debt securities of that series will be automatically accelerated and become immediately due and payable, without any action by the trustee or any holder. At any time after the trustee or the holders have accelerated any series of debt securities, but before a judgment or decree for payment of the money due has been obtained, the holders of a majority in principal amount of the outstanding debt securities of the affected series may, under certain circumstances, rescind and annul such acceleration.

        Except in cases of default where the trustee has some special duties, the trustee is not required to take any action under the applicable indenture at the request of any holders unless the holders offer the trustee reasonable protection from expenses and liability. We refer to this as an "indemnity." If reasonable indemnity is provided, the holders of not less than a majority in principal amount of the outstanding debt securities of the relevant series may direct the time, method and place of conducting any lawsuit or other formal legal action seeking any remedy available to the trustee. These majority

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holders may also direct the trustee in performing any other action under the applicable indenture, subject to certain limitations.

        Before you bypass the trustee and bring your own lawsuit or other formal legal action or take other steps to enforce your rights or protect your interests relating to the applicable indenture or debt securities issued under such indenture, the following must occur:

•

you must give the trustee written notice that an event of default has occurred and is continuing;



•

the holders of at least a majority in principal amount of all outstanding debt securities of the relevant series must make a written request that the trustee take action because of the default and must offer reasonable indemnity to the trustee against the cost and other liabilities of taking that action; and



•

the trustee must have not taken action for 60 days after receipt of the notice, request and offer of indemnity and must have not received from the holders of a majority in principal amount of all outstanding debt securities of the relevant series other conflicting directions within such 60 day period.

However, you are entitled at any time to bring a lawsuit for the payment of money due on your debt security after its due date.

        Every year we will furnish to the trustee a written statement by certain of our officers certifying that, to their best knowledge, we are in compliance with the applicable indenture and the debt securities, or else specifying any default.

Modification of an Indenture

        There are three types of changes we can make to the indentures and our debt securities:

        Changes Requiring Your Approval.    First, we cannot make certain changes to the indentures and our debt securities without the approval of each holder of debt securities affected by the change. The following is a list of those types of changes:

•

change the stated maturity of the principal of, or interest on, a debt security;



•

reduce the principal of, or the rate of interest on, a debt security;



•

reduce the amount of any premium due upon redemption;



•

reduce the amount of principal of an original issue discount security payable upon acceleration of its maturity;



•

change the currency or place of payment on a debt security;



•

impair a holder's right to sue for payment on or after the stated maturity of a debt security;



•

in the case of a subordinated debt security, modify the subordination provisions of such debt security in a manner that is adverse to the holders;



•

reduce the percentage of holders of debt securities whose consent is needed to modify or amend an indenture;



•

reduce the percentage of holders of debt securities whose consent is needed to waive compliance with certain provisions of an indenture or certain defaults and their consequences;



•

waive past defaults in the payment of principal of or premium, if any, or interest on the debt securities or in respect of any covenant or provision that cannot be modified or amended without the approval of each holder of the debt securities; or



•

modify any of the foregoing provisions.

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        Changes Requiring Majority Approval.    Second, certain changes require the approval of holders of not less than a majority in principal amount of the outstanding debt securities of the affected series. We require the same majority vote to obtain a waiver of a past default. However, we cannot obtain a waiver of a payment default or any other aspect of an indenture or the debt securities listed in the first category described above under "—Changes Requiring Your Approval" without the consent of each holder of debt securities affected by the waiver.

        Changes Not Requiring Approval.    Third, certain changes do not require any approval of holders of debt securities. These include:

•

to evidence the assumption by a successor obligor of our obligations;



•

to add to our covenants for the benefit of holders of debt securities of all or any series or to surrender any right or power conferred upon us;



•

to add any additional events of default for the benefit of holders of all or any series of debt securities;



•

to add to or change any provisions necessary to permit or facilitate the issuance of debt securities in bearer form, registrable or not registrable as to principal, and with or without interest coupons, or to permit or facilitate the issuance of debt securities in uncertificated form;



•

to add to, change or eliminate any of the provisions, so long as such addition, change or elimination does not apply to any debt security of any existing series of debt security entitled to the benefit of such provision or modify the rights of the holder of any such debt security with respect to such provision or such addition, change or elimination only becomes effective when there is no such security outstanding;



•

to add guarantees of or to secure all or any series of the debt securities;



•

to establish the forms or terms of debt securities of any series;



•

to evidence and provide for the acceptance of appointment of a successor trustee;



•

to cure any ambiguity, to correct or supplement any provision in the applicable indenture which may be defective or inconsistent with any other provision contained therein or to conform the terms of the indenture that are applicable to a series of debt securities to the description of the terms of such debt securities in the offering memorandum, prospectus supplement or other offering document applicable to such debt securities at the time of initial sale thereof;



•

to permit or facilitate the defeasance or satisfaction and discharge of debt securities of any series; provided that such action does not adversely affect the interests of any holder of debt securities in any material respect;



•

to prohibit the authentication and delivery of additional series of debt securities;



•

to add to or change or eliminate any provision as shall be necessary or desirable in accordance with any amendments to the Trust Indenture Act;



•

to comply with the rules of any applicable depositary; or



•

to change anything that does not adversely affect the interests of the holders of debt securities of any series in any material respect.

        Further Details Concerning Approval.    Debt securities are not considered outstanding, and therefore the holders thereof are not eligible to vote or consent or give their approval or take other action under the applicable indenture, if we have deposited or set aside in trust for you money for their payment or redemption or if we or one of our affiliates own them. Debt securities are also not considered to be outstanding and therefore eligible to vote or consent or give their approval or take other action under

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the applicable indenture if they have been fully defeased or discharged, as described below under "—Discharge, Defeasance and Covenant Defeasance—Discharge" or "—Full Defeasance."

Discharge, Defeasance and Covenant Defeasance

        Discharge.    We may discharge our obligations to holders of any series of debt securities that have become due and payable or will become due and payable at their stated maturity within one year, or are to be called for redemption within one year, by depositing or causing to be deposited with the trustee, in trust, funds in the applicable currency in an amount sufficient to pay the debt securities of such series, including any premium and interest to the date of such deposit (in the case of debt securities which have become due and payable) or to such stated maturity or redemption date, as applicable.

        Full Defeasance.    We can, under particular circumstances, effect a full defeasance of any series of debt securities. By this we mean we can legally release ourselves from any payment or other obligations on the debt securities if, among other things, we put in place the arrangements described below to pay those debt securities and deliver certain certificates and opinions to the trustee:

•

we must irrevocably deposit (or cause to be deposited), in trust, for the benefit of all direct holders of the debt securities of such series money or government obligations (or, in some circumstances, depository receipts representing such government obligations), or a combination thereof, that will provide funds in an amount sufficient to pay the debt securities of such series, including any premium and interest on the debt securities of such series at their stated maturity or applicable redemption date (a "government obligation" for these purposes means, with respect to any series of debt securities, securities that are not callable or redeemable at the option of the issuer thereof and are (1) direct obligations of the government that issued the currency in which such series is denominated (or, if such series is denominated in euros, the direct obligations of any government that is a member of the European Monetary Union) for the payment of which its full faith and credit is pledged or (2) obligations of a person controlled or supervised by and acting as an agency or instrumentality of such government the payment of which is unconditionally guaranteed as a full faith and credit obligation by such government); and



•

we must deliver to the trustee a legal opinion stating that the current U.S. federal income tax law has changed or an Internal Revenue Service, or IRS, ruling has been issued, in each case to the effect that holders of the outstanding debt securities of such series will not recognize gain or loss for federal income tax purposes as a result of such full defeasance and will be subject to federal income tax on the same amounts and in the same manner and at the same times as would have been the case if such full defeasance had not occurred.

        Notwithstanding the foregoing, the following rights and obligations will survive full defeasance:

•

your right to receive payments from the trust when payments are due;



•

our obligations relating to registration and transfer of debt securities and lost or mutilated certificates; and



•

our obligations to maintain a payment office and to hold moneys for payment in trust.

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        Covenant Defeasance.    Under current U.S. federal income tax law, we can make the same type of deposit described above with respect to a series of debt securities and be released from the obligations imposed by most of the covenants with respect to such series and provisions of the applicable indenture with respect to such series, and we may omit to comply with those covenants and provisions without creating an event of default. This is called "covenant defeasance."

        If we accomplish covenant defeasance, the following provisions of an indenture and the debt securities of such series would no longer apply:

•

most of the covenants applicable to such series of debt securities and any events of default for failure to comply with those covenants;



•

any subordination provisions; and



•

certain other events of default as set forth in any prospectus supplement.

Conversion and Exchange Rights

        The terms and conditions, if any, upon which the debt securities are convertible into or exchangeable for common or preferred shares, other debt securities or other property will be set forth in the applicable prospectus supplement. Such terms will include whether the debt securities are convertible into or exchangeable for common or preferred shares, other debt securities or other property, the conversion or exchange price (or manner of calculation thereof), the conversion or exchange period, whether conversion or exchange will be at the option of the holders, the events requiring an adjustment of the conversion or exchange price, provisions affecting conversion or exchange in the event of the redemption of such debt securities and any restrictions on conversion or exchange, including restrictions directed at maintaining our REIT status under the Internal Revenue Code of 1986, as amended, or the Code.

Subordination

        We will describe in the applicable prospectus supplement the terms and conditions, if any, upon which any series of senior subordinated securities or junior subordinated securities is subordinated to debt securities of another series or to our other indebtedness. The terms will include a description of:

•

the indebtedness ranking senior to the debt securities being offered;



•

the restrictions, if any, on payments to the holders of the debt securities being offered while a default with respect to the senior indebtedness is continuing;



•

the restrictions, if any, on payments to the holders of the debt securities being offered following an event of default with respect to such debt securities; and



•

provisions requiring holders of the debt securities being offered to remit payments to holders of senior indebtedness.

Global Debt Securities

        We may issue the debt securities of a series in whole or in part in the form of one or more registered global securities that we will deposit with a depositary or with a nominee for a depositary identified in the applicable prospectus supplement and registered in the name of such depositary or nominee. In such case, we will issue one or more registered global securities denominated in an amount equal to the aggregate principal amount of all of the debt securities of the series to be issued and represented by such registered global security or securities.

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        Unless and until it is exchanged in whole or in part for debt securities in definitive registered form, a registered global security may not be transferred except as a whole:

•

by the depositary for such registered global security to its nominee;



•

by a nominee of the depositary to the depositary or another nominee of the depositary; or



•

by the depositary or its nominee to a successor of the depositary or a nominee of the successor.

        The prospectus supplement relating to a series of debt securities will describe the specific terms of the depositary arrangement with respect to any portion of such series represented by a registered global security. We currently anticipate that the following provisions will apply to all depositary arrangements for debt securities:

•

ownership of beneficial interests in a registered global security will be limited to persons that have accounts with the depositary for the registered global security, those persons being referred to as "participants," or persons that may hold interests through participants;



•

upon the issuance of a registered global security, the depositary for the registered global security will credit, on its book-entry registration and transfer system, the participants' accounts with the respective principal amounts of the debt securities represented by the registered global security beneficially owned by the participants;



•

any dealers, underwriters or agents participating in the distribution of the debt securities will designate the accounts to be credited; and



•

ownership of any beneficial interest in the registered global security will be shown on, and the transfer of any ownership interest will be effected only through, records maintained by the depositary for the registered global security (with respect to interests of participants) and on the records of participants (with respect to interests of persons holding through participants).

        The laws of some states may require that certain purchasers of securities take physical delivery of the securities in definitive form. These laws may limit the ability of those persons to own, transfer or pledge beneficial interests in registered global securities.

        So long as the depositary for a registered global security, or its nominee, is the registered owner of the registered global security, the depositary or the nominee, as the case may be, will be considered the sole owner or holder of the debt securities represented by the registered global security for all purposes under the applicable indenture. Except as set forth below, owners of beneficial interests in a registered global security:

•

will not be entitled to have the debt securities represented by a registered global security registered in their names;



•

will not receive or be entitled to receive physical delivery of the debt securities in the definitive form; and



•

will not be considered the owners or holders of the debt securities under the applicable indenture.

        Accordingly, each person owning a beneficial interest in a registered global security must rely on the procedures of the depositary for the registered global security and, if the person is not a participant, on the procedures of a participant through which the person owns its interest, to exercise any rights of a holder under the applicable indenture.

        We understand that under currently existing industry practices, if we request any action of holders or if an owner of a beneficial interest in a registered global security desires to give or take any action that a holder is entitled to give or take under an indenture, the depositary for the registered global

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security would authorize the participants holding the relevant beneficial interests to give or take the action, and those participants would authorize beneficial owners owning through those participants to give or take the action or would otherwise act upon the instructions of beneficial owners holding through them.

        We will make payments of principal of and premium, if any, and interest, if any, on debt securities represented by a registered global security registered in the name of a depositary or its nominee to the depositary or its nominee, as the case may be, as the registered owners of the registered global security. Neither we nor any trustee or any other agent of us or a trustee will be responsible or liable for any aspect of the records relating to, or payments made on account of, beneficial ownership interests in the registered global security or for maintaining, supervising or reviewing any records relating to the beneficial ownership interests.

        We expect that the depositary for any debt securities represented by a registered global security, upon receipt of any payments of principal and premium, if any, and interest, if any, in respect of the registered global security, will immediately credit participants' accounts with payments in amounts proportionate to their respective beneficial interests in the registered global security as shown on the records of the depositary. We also expect that standing customer instructions and customary practices will govern payments by participants to owners of beneficial interests in the registered global security held through the participants, as is now the case with the securities held for the accounts of customers in bearer form or registered in "street name." We also expect that any of these payments will be the responsibility of the participants.

        No registered global security may be exchanged in whole or in part for debt securities registered, and no transfer of a registered global security in whole or in part may be registered, in the name of any person other than the depositary for such registered global security, unless (1) such depositary notifies us that it is unwilling or unable to continue as depositary for such registered global security or has ceased to be a clearing agency registered under the Exchange Act and we fail to appoint an eligible successor depositary within 90 days, (2) an event of default shall have occurred and be continuing with respect to such debt securities, or (3) circumstances, if any, exist in addition to or in lieu of the foregoing as have been specified for that purpose in an applicable prospectus supplement. In any such case, the affected registered global security may be exchanged in whole or in part for debt securities in definitive form and the applicable trustee will register any such debt securities in such name or names as such depositary directs.

        We currently anticipate that certain registered global securities will be deposited with, or on behalf of, The Depository Trust Company, New York, New York, or DTC, and will be registered in the name of Cede & Co., as the nominee of DTC. DTC has advised us that DTC is a limited-purpose trust company organized under the New York Banking Law, a "banking organization" within the meaning of the New York Banking Law, a member of the Federal Reserve System, a "clearing corporation" within the meaning of the New York Uniform Commercial Code and a "clearing agency" registered pursuant to the provisions of Section 17A of the Exchange Act. DTC holds securities that its participants, or direct participants, deposit with DTC. DTC also facilitates the post-trade settlement among direct participants of sales and other securities transactions in deposited securities, through electronic computerized book-entry transfers and pledges between direct participants' accounts. This eliminates the need for physical movement of securities certificates. Direct participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations, and certain other organizations. DTC is a wholly owned subsidiary of The Depository Trust & Clearing Corporation, or DTCC. DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others such as both U.S. and non-U.S. securities brokers and dealers, banks, trust companies and clearing corporations that clear through or maintain a custodial relationship with a direct participant, either directly or indirectly.

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The rules applicable to DTC and its direct participants are on file with the SEC. The information in this paragraph concerning DTC and DTC's book-entry system has been obtained from sources that we believe to be reliable, but we take no responsibility for the accuracy thereof. In the event registered global securities are deposited with, or on behalf of, a depositary other than DTC, we will describe additional or differing terms of the depositary arrangements in the applicable prospectus supplement relating to that particular series of debt securities.

        We may also issue bearer debt securities of a series in the form of one or more global securities, referred to as "bearer global securities." We currently anticipate that we will deposit these bearer global securities with a common depositary for Euroclear Bank S.A./N.V. and Clearstream Banking, société anonyme, or with a nominee for the depositary identified in the prospectus supplement relating to that series. The prospectus supplement relating to a series of debt securities represented by a bearer global security will describe the specific terms and procedures, including the specific terms of the depositary arrangement and any specific procedures for the issuance of debt securities in definitive form in exchange for a bearer global security, with respect to the portion of the series represented by a bearer global security.

        Neither we nor any trustee assumes any responsibility for the performance by DTC or any other depositary or its participants of their respective obligations, including obligations that they have under the rules and procedures that govern their operations.

Governing Law

        The indentures and our debt securities will be governed by and construed in accordance with the laws of the State of New York.

DESCRIPTION OF SHARES OF BENEFICIAL INTEREST

        References in this "Description of Shares of Beneficial Interest" section to "we," "us" or "our" mean Senior Housing Properties Trust and not any of its consolidated subsidiaries, unless the context otherwise requires. The following description of the terms of our shares of beneficial interest is only a summary. For a complete description, please refer to our declaration of trust and bylaws, which have previously been filed with the SEC and are incorporated by reference in this prospectus, and this summary is qualified in its entirety thereby.

        Our declaration of trust authorizes us to issue up to an aggregate of 300,000,000 shares of beneficial interest, all of which are currently designated as common shares of beneficial interest, par value $.01 per share, or common shares. As of June 25, 2015, we had 237,398,662 common shares issued and outstanding. As of the date of this prospectus, no other class or series of shares of beneficial interest has been established and is outstanding. Our declaration of trust contains a provision permitting our Board of Trustees, without any action by our shareholders, to amend our declaration of trust to increase or decrease the total number of shares of beneficial interest or the number of shares of any class or series that we have authority to issue. Our declaration of trust further authorizes our Board of Trustees, subject to certain limitations, to reclassify any unissued shares from time to time by setting the preferences, conversion or other rights, voting powers, restrictions, limitations as to distributions, qualifications or terms or conditions of redemption of our shares of beneficial interest or any new class or series of shares created by our Board of Trustees. We believe that giving these powers to our Board of Trustees will provide us with increased flexibility in structuring possible future financings and acquisitions and in meeting other business needs which might arise. Although our Board of Trustees has no intention at the present time of doing so, it could authorize us to issue a class or series of shares of beneficial interest that could, depending upon the terms of the class or series, delay or prevent a change in control.

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Common Shares

        The following is a summary of some general terms and provisions of our common shares. Because it is a summary, it does not contain all of the information that may be important to you. If you want more information, you should read our declaration of trust and bylaws, copies of which have been filed with the SEC. See "Where You Can Find More Information." This summary is also subject to and qualified by reference to the description of the particular terms of common shares described in the applicable prospectus supplement.

        Except as otherwise described in the applicable prospectus supplement, and subject to the preferential rights of any other class or series of shares then outstanding or which may be issued, and to the ownership restrictions described below, all of our common shares are entitled:

•

to receive distributions on our common shares if, as and when authorized by our Board of Trustees and declared by us out of assets legally available for distribution; and



•

to share ratably in our assets legally available for distribution to our shareholders in the event of our liquidation, dissolution or winding up after payment of or adequate provision for all of our known debts and liabilities.

        Subject to the provisions of our declaration of trust regarding the restriction on the transfer of shares of beneficial interest, each outstanding common share entitles the holder to one vote on all matters submitted to a vote of shareholders, including the election of trustees. Holders of our common shares do not have cumulative voting rights in the election of trustees.

        Holders of our common shares have no preference, conversion, exchange, sinking fund, redemption or appraisal rights, or preemptive rights to subscribe for any of our securities.

        For additional information about our common shares, including the potential effects that provisions in our declaration of trust and bylaws may have in delaying or preventing a change in our control, see "Description of Certain Provisions of Maryland Law and of Our Declaration of Trust and Bylaws" below.

Preferred Shares

        The following is a summary of the general terms and provisions of the preferred shares that we may offer by this prospectus. We may issue preferred shares in one or more classes or series; each class or series of preferred shares will have its own rights and preferences. We will describe in a prospectus supplement (1) the specific terms of the class or series of any preferred shares offered through that prospectus supplement and (2) any general terms outlined in this section that will not apply to such preferred shares. Because this is a summary, it does not contain all of the information that may be important to you. If you want more information, you should read our declaration of trust, including any applicable articles supplementary, and bylaws, copies of which have been filed with the SEC. See "Where You Can Find More Information." This summary is also subject to and qualified by reference to the description of the particular terms of our securities described in the applicable prospectus supplement. The prospectus supplement may add to, update or change the terms of such securities from those described below.

        General.    Our declaration of trust authorizes our Board of Trustees to determine the preferences, conversion or other rights, voting powers, restrictions, limitations as to dividends or other distributions, qualifications and terms and conditions of redemption of any preferred shares.

        The preferred shares will have the distribution, liquidation, redemption, voting and conversion rights described in this section unless we state otherwise in the applicable prospectus supplement. The liquidation preference is not indicative of the price at which the preferred shares will actually trade on

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or after the date of issuance. You should read the prospectus supplement relating to the particular class or series of the preferred shares for specific terms, including:

•

the distinctive designation of the applicable class or series of preferred shares and the number of shares that will constitute the class or series;



•

the initial offering price of such preferred shares;



•

relative ranking and preference of such preferred shares as to distribution rights and rights upon liquidation, dissolution or winding up of our affairs;



•

the distribution rate or rates (or method of calculation) on that class or series, the distribution periods, the date(s) on which distributions will be payable and whether the distributions will be cumulative, noncumulative or partially cumulative, and, if cumulative, the dates from which the distributions will start to cumulate;



•

any redemption or sinking fund provisions of that class or series;



•

any voting rights;



•

any conversion or exchange provisions;



•

any other specific terms, preferences, rights, limitations or restrictions of such preferred shares;



•

any limitations on issuance of any class or series of preferred shares ranking senior to or on a parity with such preferred shares as to distribution rights and rights upon liquidation, dissolution or winding up of our affairs;



•

any procedures for any auction and remarketing;



•

any listing of such preferred shares on any securities exchange; and



•

any limitations on record or beneficial ownership and restrictions on transfer, including those as may be appropriate to preserve our qualification for taxation as a REIT.

        Holders of our preferred shares have no preemptive rights to subscribe for any of our securities.

        We will describe in the applicable prospectus supplement any material U.S. federal income tax considerations applicable to the preferred shares offered by such prospectus supplement.

        The issuance of preferred shares, the issuance of rights to purchase preferred shares or the possibility of the issuance of preferred shares or such rights could have the effect of delaying or preventing a change in our control. In addition, the rights of holders of common shares will be subject to, and may be adversely affected by, the rights of holders of any preferred shares that we have issued or may issue in the future.

        For additional information about our preferred shares, including the potential effects that provisions in our declaration of trust and bylaws may have in delaying or preventing a change in our control, see "Description of Certain Provisions of Maryland Law and of Our Declaration of Trust and Bylaws" below.

        As described under "Description of Depositary Shares," we may, at our option, elect to offer depositary shares evidenced by depositary receipts. If we elect to do this, each depositary receipt will represent a fractional interest in a share of the particular class or series of the preferred shares issued and deposited with a depositary. The applicable prospectus supplement will specify that fractional interest.

        Rank.    Unless our Board of Trustees otherwise determines and we so specify in the applicable prospectus supplement, we expect that the preferred shares will, with respect to distribution rights and rights upon liquidation, dissolution or winding up of our affairs, rank senior to all our common shares.

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        Distributions.    Holders of preferred shares of each class or series will be entitled to receive cash and/or share distributions at the rates and on the dates shown in the applicable prospectus supplement. We will pay each distribution to holders of record as they appear on our share transfer books on the record dates fixed by our Board of Trustees. In the case of preferred shares represented by depositary receipts, the records of the depositary referred to under "Description of Depositary Shares" will determine the persons to whom distributions are payable.

        We will not authorize or pay any distributions on a class or series of preferred shares or set aside funds for the payment of distributions if restricted or prohibited by law, or if the terms of any of our agreements, including agreements relating to our indebtedness or our other classes or series of preferred shares, prohibit that authorization, payment or setting aside of funds or provide that the authorization, payment or setting aside of funds is a breach of or a default under that agreement. We are now, and may in the future become, a party to agreements which restrict or prevent the payment of distributions on, or the purchase or redemption of, our shares of beneficial interest, including preferred shares. These restrictions may be indirect, such as covenants which require us to maintain specified levels of net worth or assets.

        Distributions on any class or series of preferred shares may be cumulative, noncumulative or partially cumulative, as specified in the applicable prospectus supplement. Cumulative distributions will be cumulative from and after the date shown in the applicable prospectus supplement. If our Board of Trustees fails to authorize a distribution that is noncumulative, the holders of the applicable class or series will have no right to receive, and we will have no obligation to pay, a distribution in respect of the applicable distribution period, whether or not distributions on that class or series are declared payable in the future.

        We refer to our common shares or other shares, now or hereafter issued, that rank junior to an applicable class or series of preferred shares with respect to distribution rights as junior shares. To the extent that the applicable class or series is entitled to a cumulative distribution, we may not declare or pay any distributions, or set aside any funds for the payment of distributions, on junior shares, or redeem or otherwise acquire junior shares, unless we also have declared and either paid or set aside for payment the full cumulative distributions on such class or series of preferred shares and on all our other class or series of preferred shares ranking senior to or on a parity with such class or series of preferred shares for all past distribution periods. The preceding sentence does not prohibit:

•

distributions payable in junior shares or options, warrants or rights to subscribe for or purchase junior shares;



•

conversions into or exchanges for junior shares;



•

pro rata offers to purchase or a concurrent redemption of all, or a pro rata portion of, the outstanding preferred shares of such class or series and any other class or series of shares ranking on a parity with such class or series of preferred shares with respect to distribution rights and rights upon our liquidation, dissolution or winding up; or



•

our redemption, purchase or other acquisition of shares under incentive, benefit or share purchase plans for officers, trustees or employees or others performing or providing similar services, for the purposes of enforcing restrictions upon ownership and transfer of our equity securities contained in our declaration of trust or bylaws or our redemption or other acquisition of rights issued under any shareholder rights plan we may adopt.

        To the extent an applicable class or series is noncumulative, we need only declare, and pay or set aside for payment, the distribution for the then current distribution period, before making distributions on or acquiring junior shares.

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        Unless full cumulative distributions on a class or series of preferred shares have been or are contemporaneously declared and either paid or set aside for payment for all past distribution periods, no distributions (other than in junior shares) may be declared or paid or set aside for payment on any other class or series of preferred shares ranking on a parity with such class or series with respect to distribution rights. When distributions are not paid in full upon a class or series of preferred shares and any other class or series ranking on a parity with such class or series with respect to distribution rights, all distributions declared upon such class or series and any class or series ranking on a parity with such class or series with respect to distribution rights shall be allocated pro rata so that the amount of distributions declared per share on such class or series and such other shares shall in all cases bear to each other the same ratio that the accrued distributions per share on such class or series and such other shares bear to each other.

        Unless otherwise specified in the applicable prospectus supplement, we will credit any distribution payment made on an applicable class or series, including any capital gain distribution, first against the earliest accrued but unpaid distribution due with respect to the class or series.

        Redemption.    We may have the right or may be required to redeem one or more class or series of preferred shares, as a whole or in part, in each case upon the terms, if any, and at the times and at the redemption prices shown in the applicable prospectus supplement.

        If a class or series of preferred shares is subject to mandatory redemption, we will specify in the applicable prospectus supplement the number of shares we are required to redeem, when those redemptions start, the redemption price and any other terms and conditions affecting the redemption. The redemption price will include all accrued and unpaid distributions, except in the case of noncumulative preferred shares. The redemption price may be payable in cash or other property, as specified in the applicable prospectus supplement. If the redemption price for preferred shares of any class or series is payable only from the net proceeds of our issuance of shares of beneficial interest, the terms of the preferred shares may provide that, if no shares of beneficial interest shall have been issued or to the extent the net proceeds from any issuance are insufficient to pay in full the aggregate redemption price then due, the preferred shares will automatically and mandatorily be converted into shares of beneficial interest pursuant to conversion provisions specified in the applicable prospectus supplement.

        Liquidation Preference.    The applicable prospectus supplement will specify the liquidation preference of the applicable class or series. Upon our voluntary or involuntary liquidation, dissolution or winding up of our affairs, before any distribution may be made to the holders of our common shares or any other shares of beneficial interest ranking junior in the distribution of assets upon any liquidation, dissolution or winding up of our affairs, to the applicable class or series, the holders of that class or series will be entitled to receive, out of our assets legally available for distribution to shareholders, liquidating distributions in the amount of the liquidation preference, plus an amount equal to all distributions accrued and unpaid. In the case of a noncumulative applicable class or series, accrued and unpaid distributions include only the then current distribution period. Unless otherwise specified in the applicable prospectus supplement, if liquidating distributions have been made in full to all holders of preferred shares, our remaining assets will be distributed among the holders of any other shares of beneficial interest ranking junior to the preferred shares upon liquidation, according to their rights and preferences and in each case according to their number of shares.

        If, upon any voluntary or involuntary liquidation, dissolution or winding up of our affairs, our available assets are insufficient to pay the amount of the liquidating distributions on all outstanding shares of that class or series and the corresponding amounts payable on all equally ranking shares of beneficial interest upon any liquidation, dissolution or winding up of our affairs, then the holders of that class or series and all other equally ranking shares of beneficial interest shall share ratably in the distribution in proportion to the full liquidating distributions to which they would otherwise be entitled.

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        Unless otherwise specified in the applicable prospectus supplement, after payment of the full amount of the liquidating distribution to which they are entitled, the holders of a class or series of preferred shares will have no right or claim to any of our remaining assets. Neither the sale, lease, transfer or conveyance of all or substantially all of our property or business, nor the merger or consolidation of us into or with any other entity or the merger or consolidation of any other entity into or with us or a statutory share exchange by us, shall be deemed to constitute the dissolution, liquidation or winding up of our affairs. In determining whether a distribution (other than upon voluntary or involuntary dissolution), by dividend, redemption or other acquisition of shares or otherwise, is permitted under Maryland law, amounts that would be needed, if we were to be dissolved at the time of the distribution, to satisfy the preferential rights upon dissolution of the holders of a class or series of preferred shares will not be added to our total liabilities.

        Voting Rights.    Holders of our preferred shares will not have any voting rights, except as described below or as otherwise from time to time specified in the applicable prospectus supplement.

        Unless otherwise specified in the applicable prospectus supplement, holders of our preferred shares (voting separately as a class with all other class or series of preferred shares with similar voting rights) will be entitled to elect two additional trustees to our Board of Trustees at our next annual meeting of shareholders and at each subsequent annual meeting if at any time distributions on the applicable class or series are in arrears for six consecutive quarterly periods. If the applicable class or series has a cumulative distribution, the right to elect additional trustees described in the preceding sentence shall remain in effect until we declare and pay or set aside for payment all distributions accrued and unpaid on the applicable class or series. If the applicable class or series does not have a cumulative distribution, the right to elect additional trustees described above shall remain in effect until we declare and pay or set aside for payment distributions accrued and unpaid on four consecutive quarterly periods on the applicable class or series. In the event the preferred shareholders are so entitled to elect trustees, the entire Board of Trustees will be increased by two trustees.

        Unless otherwise provided for in an applicable class or series, so long as any preferred shares are outstanding, we may not, without the affirmative vote or consent of a majority of the shares of each affected class or series of preferred shares outstanding at that time:

•

authorize, create or increase the authorized or issued amount of any class or series of shares of beneficial interest ranking senior to that class or series of preferred shares with respect to distribution and liquidation rights;



•

reclassify any authorized shares of beneficial interest into a class or series of shares of beneficial interest ranking senior to that class or series of preferred shares with respect to distribution and liquidation rights;



•

create, authorize or issue any security or obligation convertible into or evidencing the right to purchase any shares of beneficial interest ranking senior to that class or series of preferred shares with respect to distribution and liquidation rights; and



•

amend, alter or repeal the provisions of our declaration of trust or any articles supplementary relating to that class or series of preferred shares, whether by merger, consolidation or otherwise, in a manner that materially and adversely affects the class or series of preferred shares.

The authorization, creation or increase of the authorized or issued amount of any class or series of shares of beneficial interest ranking on parity or junior to a class or series of preferred shares with respect to distribution and liquidation rights will not be deemed to materially and adversely affect that class or series. Further, with respect to any merger, consolidation or similar event, so long as a class or series of preferred shares remains outstanding with the terms thereof materially unchanged or the holders of shares of that class or series receive shares of the successor with substantially identical rights,

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taking into account that, upon the occurrence of such event, we may not be the surviving entity, the occurrence of such event will not be deemed to materially and adversely affect that class or series.

        The foregoing voting provisions will not apply if all of the outstanding shares of the class or series of preferred shares with the right to vote have been redeemed or called for redemption and sufficient funds have been deposited in trust for the redemption either at or prior to the act triggering these voting rights.

        As more fully described under "Description of Depositary Shares" below, if we elect to issue depositary shares, each representing a fraction of a share of a class or series, each depositary share will in effect be entitled to a fraction of a vote.

        Conversion and Exchange Rights.    We will describe in the applicable prospectus supplement the terms and conditions, if any, upon which you may, or we may require you to, convert or exchange shares of any class or series of preferred shares into common shares or any other class or series of shares of beneficial interest or debt securities or other property. The terms will include the number of common shares or other securities or property into which the preferred shares are convertible or exchangeable, the conversion or exchange price (or the manner of determining it), the conversion or exchange period, provisions as to whether conversion or exchange will be at the option of the holders of the class or series or at our option, the events requiring an adjustment of the conversion or exchange price and provisions affecting conversion or exchange upon the redemption of shares of the class or series.

Transfer Agent and Registrar

        The transfer agent and registrar for our common shares is Wells Fargo Bank, National Association. The transfer agent and registrar for each class or series of preferred shares that may be issued and sold pursuant to this prospectus will be designated in the applicable prospectus supplement.

DESCRIPTION OF DEPOSITARY SHARES

General

        References in this "Description of Depositary Shares" section to "we," "us" or "our" mean Senior Housing Properties Trust and not any of its consolidated subsidiaries, unless the context otherwise requires. The following is a summary of the general terms and provisions of the depositary shares that we may offer by this prospectus. Because it is a summary, it does not contain all of the information that may be important to you. If you want more information, you should read the form of deposit agreement and depositary receipts, which will be filed as exhibits to the registration statement of which this prospectus is a part prior to an offering of depositary shares. See "Where You Can Find More Information." This summary is also subject to and qualified by reference to the descriptions of the particular terms of our securities described in the applicable prospectus supplement. We will describe in a prospectus supplement (1) the specific terms of the depositary shares offered through that prospectus supplement and (2) any general terms outlined in this section that will not apply to such depositary shares. The applicable prospectus supplement also may add to, update or change the terms of such securities may differ from those described below.

        We may, at our option, elect to offer fractional interests in preferred shares, rather than whole preferred shares. If we exercise this option, we will appoint a depositary to issue depositary receipts representing those fractional interests. Preferred shares of each series represented by depositary shares will be deposited under a separate deposit agreement between us and the depositary. The prospectus supplement relating to a series of depositary shares will show the name and address of the depositary. Subject to the terms of the applicable deposit agreement, each owner of depositary shares will be

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entitled to all of the distribution, voting, conversion, redemption, liquidation and other rights and preferences of the preferred shares represented by those depositary shares.

        Depositary receipts issued pursuant to the applicable deposit agreement will evidence ownership of depositary shares. Upon surrender of depositary receipts at the office of the depositary, and upon payment of the charges provided in and subject to the terms of the deposit agreement, a holder of depositary shares will be entitled to receive the preferred shares underlying the surrendered depositary receipts.

        We will describe in the applicable prospectus supplement any material U.S. federal income tax considerations applicable to the depositary shares offered by such prospectus supplement.

Distributions

        The depositary will be required to distribute all cash distributions received in respect of the applicable preferred shares to the record holders of depositary receipts evidencing the related depositary shares, in proportion to the number of depositary receipts owned by such holders on the relevant record date, which will be the same date as the record date fixed by us for the distribution paid on the applicable preferred shares.

        If the distribution is other than in cash, a depositary will be required to distribute property received by it to the record holders of depositary receipts entitled thereto, unless the depositary determines that it is not feasible to make the distribution. In that case, the depositary may, with our approval, sell the property and distribute the net proceeds from the sale to the holders.

        Depositary shares that represent preferred shares converted or exchanged will not be entitled to distributions. The deposit agreement will also contain provisions relating to the manner in which any subscription or similar rights we offer to holders of the preferred shares will be made available to holders of depositary shares. All distributions will be subject to obligations of holders to file proofs, certificates and other information and to pay certain charges and expenses to the depositary.

Withdrawal of Preferred Shares

        You may receive the number of whole preferred shares and any money or other property represented by your depositary receipts after surrendering the depositary receipts at the corporate trust office of the depositary. Partial preferred shares will not be issued. If the depositary shares that you surrender exceed the number of depositary shares that represent the number of whole preferred shares you wish to withdraw, then the depositary will deliver to you at the same time a new depositary receipt evidencing the excess number of depositary shares. Once you have withdrawn your preferred shares, you will not be entitled to re-deposit those preferred shares under the deposit agreement in order to receive depositary shares. We do not expect that there will be any public trading market for withdrawn preferred shares.

Redemption of Depositary Shares

        If we redeem a series of the preferred shares underlying the depositary shares, the depositary will redeem those depositary shares from the proceeds received by it. The depositary will mail notice of redemption not less than 30 and not more than 60 days before the date fixed for redemption to the record holders of the depositary receipts evidencing the depositary shares being redeemed at their addresses appearing in the depositary's books. The redemption price per depositary share will be equal to the applicable fraction of the redemption price per share payable with respect to the series of the preferred shares. The redemption date for depositary shares will be the same as that of the preferred shares. If we are redeeming less than all of the depositary shares, the depositary will select the depositary shares we are redeeming by lot or pro rata as the depositary may determine.

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        After the date fixed for redemption, the depositary shares called for redemption will no longer be deemed outstanding. All rights of the holders of the depositary shares and the related depositary receipts will cease at that time, except the right to receive the money or other property to which the holders of depositary shares were entitled upon redemption. Receipt of the money or other property is subject to surrender to the depositary of the depositary receipts evidencing the redeemed depositary shares.

Voting of the Preferred Shares

        Upon receipt of notice of any meeting at which the holders of the applicable preferred shares are entitled to vote, a depositary will be required to mail the information contained in the notice of meeting to the record holders of the applicable depositary receipts. Each record holder of depositary receipts on the record date, which will be the same date as the record date for voting preferred shares, will be entitled to instruct the depositary as to the exercise of the voting rights pertaining to the amount of preferred shares represented by the holder's depositary shares. If you do not instruct the depositary how to vote your shares, the depositary will abstain from voting those shares. The depositary will not be responsible for any failure to carry out an instruction to vote or for the effect of any such vote made so long as the action or inaction of the depositary is in good faith and is not the result of the depositary's gross negligence or willful misconduct.

Liquidation Preference

        Upon our liquidation, whether voluntary or involuntary, each holder of depositary shares will be entitled to the fraction of the liquidation preference accorded each preferred share represented by the depositary shares, as described in the applicable prospectus supplement.

Conversion or Exchange of Preferred Shares

        The depositary shares will not themselves be convertible into or exchangeable for common shares, preferred shares or any of our other securities or property. Nevertheless, if so specified in the applicable prospectus supplement, the depositary receipts may be surrendered by holders to the applicable depositary with written instructions to it to instruct us to cause conversion or exchange of the preferred shares represented by the depositary shares. Similarly, if so specified in the applicable prospectus supplement, we may require you to surrender all of your depositary receipts to the applicable depositary upon our requiring the conversion or exchange of the preferred shares represented by the depositary shares. We will agree that, upon receipt of the instruction and any amounts payable in connection with the conversion or exchange, we will cause the conversion or exchange using the same procedures as those provided for delivery of preferred shares to effect the conversion or exchange. If you are converting or exchanging only a part of the depositary shares, the depositary will issue you a new depositary receipt for any unconverted or unexchanged depositary shares.

Amendment and Termination of a Deposit Agreement

        We and the applicable depositary are permitted to amend the provisions of the depositary receipts and the deposit agreement. However, the holders of a majority of the applicable depositary shares then outstanding must approve any amendment that adds or increases fees or charges or prejudices an important right of holders. Every holder of an outstanding depositary receipt at the time any amendment becomes effective, by continuing to hold the receipt, will be bound by the applicable deposit agreement, as amended.

        Any deposit agreement may be terminated by us upon not less than 30 days' prior written notice to the applicable depositary if (1) the termination is necessary to preserve our qualification for taxation as

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a REIT or (2) a majority of each series of preferred shares affected by the termination consents to the termination. When either event occurs, the depositary will be required to deliver or make available to each holder of depositary receipts, upon surrender of the depositary receipts held by the holder, the number of whole or fractional preferred shares as are represented by the depositary shares evidenced by the depositary receipts, together with any other property held by the depositary with respect to the depositary receipts. In addition, a deposit agreement will automatically terminate if:

•

all depositary shares have been redeemed;



•

there shall have been a final distribution in respect of the related preferred shares in connection with our liquidation and the distribution has been made to the holders of depositary receipts evidencing the depositary shares underlying the preferred shares; or



•

each related preferred share shall have been converted or exchanged into securities not represented by depositary shares.

Charges of a Depositary

        We will pay all transfer and other taxes and governmental charges arising solely from the existence of a deposit agreement. In addition, we will pay the fees and expenses of a depositary in connection with the initial deposit of the preferred shares and any redemption of preferred shares. However, holders of depositary receipts will pay any transfer or other governmental charges and the fees and expenses of a depositary for any duties the holders request to be performed that are outside of those expressly provided for in the applicable deposit agreement.

Resignation and Removal of Depositary

        A depositary may resign at any time by delivering to us notice of its election to do so. In addition, we may at any time remove a depositary. Any resignation or removal will take effect when we appoint a successor depositary and it accepts the appointment. We must appoint a successor depositary within 60 days after delivery of the notice of resignation or removal. A depositary must be a bank or trust company having its principal office in the United States that has a combined capital and surplus of at least $50 million.

Miscellaneous

        The depositary will be required to forward to holders of depositary receipts any reports and communications from us that it receives with respect to the related preferred shares. Holders of depository receipts will be able to inspect the transfer books of the depository and the list of holders of depositary receipts upon reasonable notice.

        Neither we nor the depositary will be liable if the depositary is prevented from or delayed in performing its obligations under a deposit agreement by law or any circumstances beyond its control. Our obligations and those of the depositary under a deposit agreement will be limited to performing duties in good faith and without gross negligence or willful misconduct. Neither we nor the depositary will be obligated to prosecute or defend any legal proceeding in respect of any depositary receipts, depositary shares or related preferred shares unless satisfactory indemnity is furnished. We and the depositary will be permitted to rely on written advice of counsel or accountants, on information provided by persons presenting preferred shares for deposit, by holders of depositary receipts, or by other persons believed in good faith to be competent to give the information, and on documents believed in good faith to be genuine and signed by a proper party.

        If the depositary receives conflicting claims, requests or instructions from any holders of depositary receipts, on the one hand, and us, on the other hand, the depositary shall be entitled to act on the claims, requests or instructions received from us.

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DESCRIPTION OF WARRANTS

        References in this "Description of Warrants" section to "we," "us" or "our" mean Senior Housing Properties Trust and not any of its consolidated subsidiaries, unless the context otherwise requires. The following is a summary of the general terms and provisions of the warrants that we may offer by this prospectus. Because it is a summary, it does not contain all of the information that may be important to you. If you want more information, you should read the forms of warrants and the warrant agreement which will be filed as exhibits to the registration statement of which this prospectus is a part. See "Where You Can Find More Information." This summary is also subject to and qualified by reference to the descriptions of the particular terms of our securities described in the applicable prospectus supplement. We will describe in a prospectus supplement (1) the specific terms of the warrants offered through that prospectus supplement and (2) any general terms outlined in this section that will not apply to such warrants. The applicable prospectus supplement also may add to, update or change the terms of such securities from those described below.

        We may issue, together with any other securities being offered or separately, warrants entitling the holder to purchase from or sell to us, or to receive from us the cash value of the right to purchase or sell, debt securities, preferred shares, depositary shares or common shares. We and a warrant agent will enter a warrant agreement pursuant to which the warrants will be issued. The warrant agent will act solely as our agent in connection with the warrants and will not assume any obligation or relationship of agency or trust for or with any holders or beneficial owners of warrants. We will file a copy of the forms of warrants and the warrant agreement with the SEC at or before the time of the offering of the applicable series of warrants.

        In the case of each series of warrants, the applicable prospectus supplement will describe the terms of the warrants being offered thereby. These include the following, if applicable:

•

the offering price;



•

the currencies in which such warrants are being offered;



•

the number of warrants offered;



•

the securities underlying the warrants;



•

the exercise price, the procedures for exercise of the warrants and the circumstances, if any, that will cause the warrants to be automatically exercised;



•

the date on which the warrants will expire;



•

the rights, if any, we have to redeem the warrants;



•

the name of the warrant agent; and



•

the other terms of the warrants.

        We will describe in the applicable prospectus supplement any material U.S. federal income tax considerations applicable to the warrants offered by such prospectus supplement.

        Warrants may be exercised at the appropriate office of the warrant agent or any other office indicated in the applicable prospectus supplement. Before the exercise of warrants, holders will not have any of the rights of holders of the securities purchasable upon exercise and will not be entitled to payments made to holders of those securities.

        The warrant agreement may be amended or supplemented without the consent of the holders of the warrants to which the amendment or supplement applies to effect changes that are not inconsistent with the provisions of the warrants and that do not adversely affect the interests of the holders of the warrants. However, any amendment that materially and adversely alters the rights of the holders of

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warrants will not be effective unless the holders of a majority of the applicable warrants then outstanding approve the amendment. Every holder of an outstanding warrant at the time any amendment becomes effective, by continuing to hold the warrant, will be bound by the applicable warrant agreement as amended thereby. The prospectus supplement applicable to a particular series of warrants may provide that certain provisions of the warrants, including the securities for which they may be exercisable, the exercise price and the expiration date may not be altered without the consent of the holder of each warrant.

DESCRIPTION OF CERTAIN PROVISIONS OF MARYLAND LAW
AND OF OUR DECLARATION OF TRUST AND BYLAWS

        We are organized as a REIT under Maryland law. The following is a summary of our declaration of trust and bylaws and several provisions of Maryland law. Because it is a summary, it does not contain all the information that may be important to you. If you want more information, you should read our entire declaration of trust and bylaws, copies of which we have filed with the SEC, and the provisions of Maryland law.

Trustees

        Our declaration of trust and bylaws provide for a Board of Trustees of five members and that our Board of Trustees may change the number of trustees, but there may be not less than three nor more than seven. In case of failure to elect trustees at an annual meeting of shareholders, the incumbent trustees will hold over and continue to direct the management of our business and affairs until they resign or their successors are elected and qualify. Any vacancy on the Board of Trustees may be filled only by a majority of the remaining trustees, even if the remaining trustees do not constitute a quorum. Any trustee elected to fill a vacancy will hold office for the remainder of the full term of the class of trustees in which the vacancy occurred or was created and until a successor is elected and qualifies.

        There is no cumulative voting in the election of trustees. Except as may be mandated by any applicable law or the listing requirements of the principal exchange on which our common shares are listed, and subject to the voting rights of any class or series of our shares which may be hereafter created, (1) a plurality of all the votes cast at a meeting of our shareholders duly called and at which a quorum is present shall be sufficient to elect a trustee in an uncontested election of trustees and (2) a majority of all the shares entitled to vote at a meeting of our shareholders duly called and at which a quorum is present shall be sufficient to elect a trustee in a contested election (which is an election at which the number of nominees exceeds the number of trustees to be elected at such meeting). Under our Governance Guidelines, if an incumbent trustee does not receive a majority of the votes cast in an uncontested election, the trustee will submit an offer to resign from the Board of Trustees. In such circumstance, the Nominating and Governance Committee of our Board of Trustees will make a recommendation to the Board on whether to accept or reject the resignation, or whether other action should be taken.

        Our declaration of trust previously divided our Board of Trustees into three classes, with shareholders electing the trustees of each class for three year terms and only one class of trustees being elected each year. Pursuant to an amendment to our declaration of trust approved at our 2014 annual meeting of shareholders, effective at our 2015 annual meeting of shareholders, trustees of the class of trustees whose term expired at that meeting or that expires at a subsequent annual meeting of shareholders are elected annually, with all of our trustees being elected annually as of our 2017 annual meeting of shareholders. The classified board provision, to the extent it is in effect, could have the effect of making the replacement of our incumbent trustees more time consuming and difficult.

        Under our bylaws, our trustees are qualified as "independent trustees" or "managing trustees," and our bylaws require that (except for temporary periods due to vacancies), a majority of the trustees

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holding office will at all times be independent trustees. For those purposes, an "independent trustee" is not involved in our day to day activities, is not an employee of our manager, RMR LLC, and qualifies as independent under our declaration of trust, if applicable, and applicable rules of the NYSE and the SEC. A "managing trustee" is a trustee who is not an independent trustee and who has been an employee of RMR LLC or has been involved in our day to day activities for at least one year prior to his or her election. Our Board of Trustees is currently composed of three independent trustees and two managing trustees.

        Our declaration of trust and bylaws provide that a trustee may be removed with or without cause by the affirmative vote of the holders of not less than two-thirds of our common shares entitled to vote in the election of trustees. This provision precludes shareholders from removing our incumbent trustees unless they can obtain the requisite affirmative vote of shares. Under our bylaws, a trustee may also be removed with or without cause by the affirmative vote of all the remaining trustees.

Advance Notice of Trustee Nominations and New Business

        Annual Meetings of Shareholders.    Our bylaws provide that nominations of individuals for election to our Board of Trustees and proposals of other business to be considered at an annual meeting of shareholders may be made only in our notice of the meeting, by or at the direction of our Board of Trustees, or by a shareholder who is entitled to vote at the meeting, is entitled to make nominations or proposals and has complied with the advance notice procedures set forth in our bylaws.

        Under our bylaws, a shareholder's written notice of nominations for trustee or other matters to be considered at an annual meeting of shareholders must be delivered to our Secretary at our principal executive offices not later than 5:00 p.m. (Eastern Time) on the 120th day nor earlier than the 150th day prior to the first anniversary of the date of our proxy statement for the preceding year's annual meeting; provided however, that in the event that the annual meeting is called for a date that is more than 30 days earlier or later than the first anniversary of the date of the preceding year's annual meeting, the notice must be delivered by not later than 5:00 p.m. (Eastern Time) on the 10th day following the earlier of the day on which (1) notice of the date of the annual meeting is mailed or otherwise made available or (2) public announcement of the date of the annual meeting is first made by us. Neither the postponement or adjournment of an annual meeting, nor the public announcement of such postponement or adjournment, commences a new time period for the giving of a shareholder's notice.

        Our bylaws set forth procedures for submission of nominations for trustee elections and other proposals by our shareholders for consideration at an annual meeting of shareholders, including, among other things:

•

requiring that a shareholder wishing to make a nomination or proposal of other business be a shareholder of record of at least $2,000 in market value, or 1% of our shares, entitled to propose such business and to vote at the meeting on such proposal for at least one year immediately preceding such shareholder's submission of a notice of the proposal, that the shareholder continue to be such a shareholder at the time of submitting its notice of such proposal through and including the time of the annual meeting (including any adjournment or postponement thereof), that the shareholder hold a certificate for such shares at the time of submitting a notice through and including the time of the annual meeting (including any adjournment or postponement thereof), and that the shareholder submit the proposal to our Secretary in accordance with the requirements of our bylaws;



•

providing that the advance notice provisions in our bylaws are the exclusive means for a shareholder to make nominations or propose business for consideration at an annual meeting of shareholders, except to the extent of matters which are required to be presented to our

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shareholders by applicable law and which have been properly presented in accordance with the requirements of such law;

•

requiring certain information to be provided regarding any proposed nominee by the proposing shareholder;



•

requiring certain information to be provided with respect to any business other than the election of trustees that a shareholder proposes to bring before a meeting of our shareholders;



•

requiring certain information to be provided as to the shareholder giving the notice and certain of its affiliates; and



•

providing that the proposing shareholder is responsible for ensuring compliance with the advance notice provisions, that any responses of the shareholder to any request for information will not cure any defect in the shareholder's notice and that neither we, our Board of Trustees or any committee of our Board of Trustees nor any of our officers has any duty to request clarification or update information or inform the proposing shareholder of any defect in the shareholder's notice.

        Special Meetings of Shareholders.    With respect to special meetings of shareholders, our bylaws provide that only business brought before the meeting pursuant to our notice of the meeting may be conducted at such meeting. Nominations of individuals for election to our Board of Trustees may be made at a special meeting of shareholders at which trustees are to be elected pursuant to our notice of meeting, by or at the direction of our Board of Trustees, or, provided that our Board of Trustees has determined that trustees will be elected at such special meeting, by a shareholder who is entitled to vote at the meeting and has complied with the advance notice procedures set forth in our bylaws. Under our bylaws, in the event we call a special meeting of shareholders for the purpose of electing one or more trustees, a shareholder may nominate an individual or individuals (as the case may be) for election as a trustee if the shareholder provides timely notice, in writing, to our Secretary at our principal executive offices, containing the information and following the procedures required by the advance notice provisions in our bylaws, as described above for submitting nominations for consideration at an annual meeting of shareholders. To be timely, a shareholder's notice must be delivered not earlier than the 150th day prior to such special meeting and not later than 5:00 p.m. (Eastern Time) on the later of (1) the 120th day prior to such special meeting or (2) the 10th day following the day on which public announcement is first made of the date of the special meeting and of any nominee proposed by the trustees to be elected at such meeting. Neither the postponement or adjournment of a special meeting, nor the public announcement of such postponement or adjournment, shall commence a new time period for the giving of a shareholder's notice.

Meetings of Shareholders; Actions by Written Consent

        Meetings of shareholders may be called only by our Board of Trustees.

        Whenever shareholders are required or permitted to take any action by a vote, the action may only be taken by a vote at a shareholders meeting. Under our bylaws, shareholders do not have the right to take any action by written consent instead of a vote at a shareholders meeting.

Liability and Indemnification of Trustees and Officers

        The laws relating to Maryland real estate investment trusts, or the Maryland REIT Law, permit a REIT formed under Maryland law to include in its declaration of trust a provision limiting the liability of its trustees and officers to the trust and its shareholders for money damages except for liability resulting from (1) actual receipt of an improper benefit or profit in money, property or services or (2) active and deliberate dishonesty by the trustee or officer that was established by a final judgment as

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being material to the cause of action adjudicated. Our declaration of trust contains such a provision which eliminates such liability to the maximum extent permitted by Maryland law.

        The Maryland REIT Law permits a REIT formed under Maryland law to indemnify and advance expenses to its trustees, officers, employees and agents to the same extent permitted by the Maryland General Corporation Law, or the MGCL, for directors and officers of Maryland corporations. The MGCL permits a corporation to indemnify its present and former directors and officers, among others, against judgments, penalties, fines, settlements and reasonable expenses actually incurred by them in connection with any proceeding to which they may be made, or are threatened to be made, a party by reason of their service in those capacities. However, a Maryland corporation is not permitted to provide this type of indemnification if the following is established:

•

the act or omission of the director or officer was material to the matter giving rise to the proceeding and (1) was committed in bad faith or (2) was the result of active and deliberate dishonesty;



•

the director or officer actually received an improper personal benefit in money, property or services; or



•

in the case of any criminal proceeding, the director or officer had reasonable cause to believe that the act or omission was unlawful.

        Under the MGCL, a Maryland corporation may not indemnify a director for an adverse judgment in a suit by or in the right of the corporation or for a judgment of liability on the basis that personal benefit was improperly received, unless in either case a court orders indemnification and then only for expenses. The MGCL permits a corporation to advance reasonable expenses to a director or officer upon the corporation's receipt of the following:

•

a written affirmation by the director or officer of his or her good faith belief that the director or officer has met the standard of conduct necessary for indemnification by the corporation; and



•

a written undertaking by the director or officer or on his or her behalf to repay the amount paid or reimbursed by the corporation if it is ultimately determined that this standard of conduct was not met.

        Our declaration of trust requires us, to the maximum extent permitted by Maryland law, to indemnify (1) any present or former trustee or officer of our company or (2) any individual who, while a trustee or officer of our company, at our request, serves or has served as a trustee, director, officer, partner employee or agent of another REIT, corporation, partnership, joint venture, trust, employee benefit plan or other enterprise and who is made or threatened to be made a party to a proceeding by reason of his or her service in that capacity and to pay or reimburse their reasonable expenses in advance of final disposition of the proceeding. Our declaration of trust also permits us to indemnify and advance expenses to any person who served any predecessor of ours in the capacities described above and any present or former shareholder, employee or agent of us or any such predecessor. Our declaration of trust also obligates us to pay or reimburse the people described above for reasonable expenses in advance of final disposition of a proceeding.

        We have also entered into indemnification agreements with our trustees and our officers providing for contractual indemnification and procedures for indemnification by us to the fullest extent permitted by law and advancements by us of certain expenses and costs relating to claims, suits or proceedings arising from their service to us.

        The SEC has expressed the opinion that indemnification of trustees, officers or persons otherwise controlling a company for liabilities arising under the Securities Act is against public policy and is therefore unenforceable.

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Shareholder Liability

        Under the Maryland REIT Law, a shareholder is generally not personally liable for the obligations of a REIT formed under Maryland law solely as a result of his or her status as a shareholder. Our declaration of trust provides that no shareholder will be liable for any debt, claim, demand, judgment or obligation of any kind by reason of being a shareholder. While we intend to conduct our business in a manner designed to minimize potential shareholder liability, we can give no assurance that you can avoid liability in all instances in all jurisdictions. We have not provided in the past and do not intend to provide insurance covering these risks to our shareholders.

        Our declaration of trust and bylaws provide that, to the fullest extent permitted by law, any shareholder who violates the declaration of trust or bylaws will indemnify us and hold us harmless from and against all costs, expenses, penalties, fines and other amounts, including attorneys' and other professional fees, arising from the shareholder's violation, together with interest on such amounts. Our bylaws further provide that matters for which a shareholder is liable and obligated to indemnify and hold us harmless include any breach or failure to fully comply with any covenant, condition or provision of our declaration of trust or bylaws, including the advance notice provisions pertaining to shareholder nominations and other proposals, and these provisions of our declaration of trust and bylaws apply to derivative actions brought against us in which the shareholder is not the prevailing party.

Disputes by Shareholders

        Our bylaws provide that actions brought against us or any trustee, officer, manager (including RMR LLC or its successor), agent or employee of us, by a shareholder, including derivative and class actions, shall, on the demand of any party to such dispute, be resolved through binding arbitration in accordance with the procedures set forth in our bylaws.

Transactions with Affiliates

        Our declaration of trust allows us to enter into contracts and transactions of any kind with any person, including any of our trustees, officers, employees or agents or any person affiliated with them. Other than general legal principles applicable to self-dealing by trustees and interested trustee transactions, there are no prohibitions in our declaration of trust or bylaws which would prohibit dealings between us and our affiliates.

Restrictions on Transfer of Shares

        Our declaration of trust provides that no person may own, or be deemed to own by virtue of the attribution provisions of the Code, more than 9.8% of the number or value of our outstanding shares or 9.8% in number or value, whichever is more restrictive, of our outstanding common shares. Our declaration of trust also prohibits any person from beneficially or constructively owning shares if that ownership would result in us being closely held under Section 856(h) of the Code or would otherwise cause us to fail to qualify for taxation as a REIT.

        Our Board of Trustees, in its discretion, may exempt a proposed transferee from the share ownership limitation if (1) it obtains such representations and undertakings from the person who makes a request therefor, as are reasonably necessary to ascertain that no individual's ownership of shares would result in our being closely held under Section 856(h) of the Code or our otherwise failing to qualify for taxation as a REIT; (2) such person does not and represents that it will not own, actually or constructively, an interest in one of our tenants (or a tenant of any entity which we own or control) that would cause us to own, actually or constructively, more than a 9.9% interest in the tenant; and (3) such person agrees that any violation or attempted violation of such representations or undertakings (or other action which is contrary to the restrictions contained in our declaration of trust) will result in such shares being automatically transferred to a charitable trust in accordance with our declaration of

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trust. In connection with any requested exemption, our Board of Trustees may require such rulings from the IRS or opinions of counsel as it deems advisable in order to determine or ensure our qualification for taxation as a REIT and such representations, undertakings and agreements it deems advisable in order for it to make the foregoing determinations.

        In determining whether to grant an exemption, our Board of Trustees may consider, among other factors, the following:

•

the general reputation and moral character of the person requesting an exemption;



•

whether the person's ownership of shares would be direct or through ownership attribution;



•

whether the person's ownership of shares would adversely affect our ability to acquire additional properties or engage in other business; and



•

whether granting an exemption would adversely affect any of our existing contractual arrangements.

        If a person attempts a transfer of our shares in violation of the ownership limitations described above, then the number of shares which would cause the violation will (a) be automatically transferred to a charitable trust for the exclusive benefit of one or more charitable beneficiaries designated by us or (b) if such transfer is not effective to prevent the violation of the ownership limitations, be void ab initio. A transfer to the charitable trust will be deemed to be effective as of the close of business on the business day prior to the purported transfer or other event that results in the transfer to the charitable trust. The prohibited owner will not acquire any rights in these excess shares, will not benefit economically from ownership of any excess shares, will have no rights to distributions and will not possess any rights to vote.

        Shares of beneficial interest held in the trust shall be issued and outstanding shares of beneficial interest. The trustee of the charitable trust shall have all voting rights and rights to distributions with respect to shares of beneficial interest held in the charitable trust, which rights shall be exercised for the exclusive benefit of the charitable beneficiary. Any distribution paid prior to the discovery by us that shares of beneficial interest have been transferred to the trustee shall be paid by the recipient of such distribution to the trustee upon demand, and any distribution authorized but unpaid shall be paid when due to the trustee. Any distribution so paid to the trustee shall be held in trust for the charitable beneficiary. The proposed transferee shall have no voting rights with respect to shares of beneficial interest held in the trust and, subject to Maryland law, the trustee of the charitable trust will have the authority to rescind as void any vote cast by the proposed transferee prior to our discovery that the shares have been transferred to the trust and to recast the vote in accordance with the desires of the trustee acting for the benefit of the charitable beneficiary. However, if we have already taken irreversible trust action, then the trustee will not have the authority to rescind and recast the vote.

        Within 20 days after receiving notice from us that our shares have been transferred to a charitable trust, the trustee will sell the shares held in the charitable trust to a person designated by the trustee whose ownership of the shares will not violate the ownership limitations set forth in our declaration of trust. Upon this sale, the interest of the charitable beneficiary in the shares sold will terminate and the trustee will distribute the net proceeds of the sale to the prohibited owner and to the charitable beneficiary as follows:

•

the prohibited owner will receive the lesser of:



(1)

the price paid by the prohibited owner for the shares or, if the prohibited owner did not give value for the shares in connection with the event causing the shares to be held in the charitable trust, for example, a gift, devise or other similar transaction, the market price (as defined in our declaration of trust) of the shares on the day of the event causing the shares to be transferred to the charitable trust; and

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(2)

the price per share received by the trustee from the sale of the shares held in the charitable trust.

•

any net sale proceeds in excess of the amount payable to the prohibited owner shall be paid immediately to the charitable beneficiary.

        If, prior to our discovery that shares have been transferred to the charitable trust, a prohibited owner sells those shares, then:

•

those shares will be deemed to have been sold on behalf of the charitable trust; and



•

to the extent that the prohibited owner received an amount for those shares that exceeds the amount that the prohibited owner was entitled to receive from a sale by a trustee, the prohibited owner must pay the excess to the trustee upon demand.

        Also, shares held in the charitable trust will be offered for sale to us, or our designee, at a price per share equal to the lesser of:

•

the price per share in the transaction that resulted in the transfer to the charitable trust or, in the case of a devise or gift, the market price at the time of the devise or gift; and



•

the market price on the date we or our designee accepts the offer.

        We will have the right to accept the offer until the trustee has sold the shares held in the charitable trust. The net proceeds of the sale to us will be distributed to the prohibited owner.

        Any person who acquires or attempts or intends to acquire beneficial or constructive ownership of any shares that will or may violate the foregoing share ownership limitations, or any person who would have owned shares that resulted in a transfer to a charitable trust, is required to immediately give written notice to us of such event, or in the case of such a proposed or attempted transaction, give at least 15 days' prior written notice, and to provide to us such other information as we may request.

        Every owner of more than 5% of our shares is required to give written notice to us within 30 days after the end of each taxable year stating the name and address of the owner, the number of our shares which the owner beneficially owns and a description of the manner in which those shares are held. If the Code or applicable tax regulations specify a threshold below 5%, this notice provision will apply to those persons who own our shares of beneficial interest at the lower percentage. In addition, each shareholder is required to provide us upon demand with any additional information that we may request in order to determine our qualification for taxation as a REIT, to ensure compliance with the foregoing share ownership limitations and determine our compliance with the requirements of any taxing authority or government.

        The restrictions in our declaration of trust described above will not preclude the settlement of any transaction entered into through the facilities of any national securities exchange or automated interdealer quotation system. Our declaration of trust provides, however, that the fact that the settlement of any transaction occurs will not negate the effect of any of the foregoing limitations and any transferee in this kind of transaction will be subject to all of the provisions and limitations described above.

        All certificates evidencing our shares and any share statements for our uncertificated shares may bear legends referring to the foregoing restrictions.

        The restrictions on transfer in our governing documents are intended to assist with REIT compliance under the Code and otherwise to promote our orderly governance. These restrictions do not apply to RMR LLC or its affiliates.

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Regulatory Compliance and Disclosure

        Our bylaws provide that any shareholder who, by virtue of such shareholder's ownership of our shares of beneficial interest or actions taken by the shareholder affecting us, triggers the application of any requirement or regulation of any federal, state, municipal or other governmental or regulatory body on us or any of our subsidiaries shall promptly take all actions necessary and fully cooperate with us to ensure that such requirements or regulations are satisfied without restricting, imposing additional obligations on or in any way limiting the business, assets, operations or prospects of us or any of our subsidiaries. If the shareholder fails or is otherwise unable to promptly take such actions so as to cause satisfaction of such requirements or regulations, such shareholder shall promptly divest a sufficient number of our shares necessary to cause the application of such requirement or regulation to not apply to us or any of our subsidiaries. If the shareholder fails to cause such satisfaction or divest itself of such sufficient number of our shares by not later than the 10th day after triggering such requirement or regulation referred to in the bylaws, then any of our shares beneficially owned by such shareholder at and in excess of the level triggering the application of such requirement or regulation shall, to the fullest extent permitted by law, be deemed to constitute shares held in violation of the ownership limitations set forth in the declaration of trust. Also, our bylaws provide that if the shareholder who triggers the application of any regulation or requirement fails to satisfy the requirements or regulations or to take curative actions within such 10 day period, we may take all other actions which the Board of Trustees deems appropriate to require compliance or to preserve the value of our assets, and we may charge the offending shareholder for our costs and expenses as well as any damages which may result.

        Our bylaws also provide that if a shareholder, by virtue of such shareholder's ownership of our shares of beneficial interest or its receipt or exercise of proxies to vote shares owned by other shareholders, would not be permitted to vote such shareholder's shares or proxies for such shares in excess of a certain amount pursuant to applicable law but the Board of Trustees determines that the excess shares or shares represented by the excess proxies are necessary to obtain a quorum, then such shareholder shall not be entitled to vote any such excess shares or proxies, and instead such excess shares or proxies may, to the fullest extent permitted by law, be voted by the Advisor (as defined in our declaration of trust) or another person designated by the Board of Trustees, in proportion to the total shares otherwise voted on such matter.

Business Combinations

        The MGCL contains a provision which regulates business combinations with interested shareholders. This provision applies to REITs formed under Maryland law like us. Under the MGCL, business combinations such as mergers, consolidations, share exchanges, or, in circumstances specified in the statute, an asset transfer or issuance or reclassification of equity securities between a REIT formed under Maryland law and an interested shareholder or an affiliate of an interested shareholder are prohibited for five years after the most recent date on which the interested shareholder becomes an interested shareholder. Under the MGCL the following persons are deemed to be interested shareholders:

•

any person who beneficially owns, directly or indirectly, 10% or more of the voting power of the trust's outstanding voting shares; or



•

an affiliate or associate of the trust who, at any time within the two-year period immediately prior to the date in question, was the beneficial owner, directly or indirectly, of 10% or more of the voting power of the then outstanding voting shares of the trust.

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        After the five year prohibition period has ended, a business combination between a trust and an interested shareholder generally must be recommended by the board of trustees of the trust and must receive the following shareholder approvals:

•

the affirmative vote of at least 80% of the votes entitled to be cast by holders of outstanding voting shares of the trust; and



•

the affirmative vote of at least two-thirds of the votes entitled to be cast by holders of voting shares other than shares held by the interested shareholder with whom or with whose affiliate or associate the business combination is to be effected or held by an affiliate or associate of the interested shareholder.

        The shareholder approvals discussed above are not required if the trust's shareholders receive the minimum price set forth in the MGCL for their shares and the consideration is received in cash or in the same form as previously paid by the interested shareholder for its shares.

        The foregoing provisions of the MGCL do not apply, however, to business combinations that are approved or exempted by our Board of Trustees prior to the time that the interested shareholder becomes an interested shareholder. A person is not an interested shareholder under the statute if the board of trustees approves in advance the transaction by which that shareholder otherwise would have become an interested shareholder. Our Board of Trustees has adopted a resolution that any business combination between us and any other person is exempted from the provisions of the MGCL described in the preceding paragraphs, provided that the business combination is first approved by our Board of Trustees, including the approval of a majority of the members of our Board of Trustees who are not affiliates or associates of the interested shareholder. This resolution, however, may be altered or repealed in whole or in part at any time.

Control Share Acquisitions

        The MGCL contains a provision which regulates control share acquisitions. This provision applies to REITs formed under Maryland law like us. The MGCL provides that control shares of a REIT formed under Maryland law acquired in a control share acquisition have no voting rights except to the extent that the acquisition is approved by a vote of two thirds of the votes entitled to be cast on the matter, excluding shares owned by the acquiror, by officers or by trustees who are employees of the trust. Control shares are voting shares, which, if aggregated with all other shares previously acquired by the acquiror, or in respect of which the acquiror is able to exercise or direct the exercise of voting power (except solely by virtue of a revocable proxy), would entitle the acquiror to exercise voting power in electing trustees within one of the following ranges of voting power:

•

one-tenth or more but less than one-third;



•

one-third or more but less than a majority; or



•

a majority or more of all voting power.

        An acquiror must obtain the necessary shareholder approval each time it acquires control shares in an amount sufficient to cross one of the thresholds noted above.

        Control shares do not include shares which the acquiring person is entitled to vote as a result of having previously obtained shareholder approval. The MGCL provides for certain exceptions from the definition of control share acquisition.

        A person who has made or proposes to make a control share acquisition, upon satisfaction of the conditions set forth in the statute, including an undertaking to pay the expenses of the meeting, may compel the board of trustees of the trust to call a special meeting of shareholders to be held within

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50 days of demand to consider the voting rights of the shares. If no request for a meeting is made, the trust may itself present the matter at any shareholders meeting.

        The trust may not redeem shares for which voting rights have previously been approved. Fair value is determined without regard to the absence of voting rights for the control shares. If voting rights for control shares are approved at a shareholders meeting and the acquiror becomes entitled to vote a majority of the shares entitled to vote, the control share acquisition statute of the MGCL generally provides that all other shareholders would have the right to exercise appraisal rights. The fair value of the shares as determined for purposes of these appraisal rights may not be less than the highest price per share paid by the acquiror in the control share acquisition.

        The control share acquisition statute of the MGCL does not apply to the following:

•

shares acquired in a merger, consolidation or share exchange if the trust is a party to the transaction; or



•

acquisitions approved or exempted by a provision in the declaration of trust or bylaws of the trust adopted before the acquisition of shares.

        Our bylaws contain a provision exempting any and all acquisitions by any person of our common shares from the control share acquisition statute. This provision may be amended or eliminated at any time in the future. Nevertheless, even if the bylaw provision is amended or eliminated, if voting rights for control shares are approved at a shareholders meeting and the acquiror becomes entitled to vote a majority of the shares entitled to vote, our declaration of trust provides that our shareholders may not exercise appraisal rights unless the Board of Trustees expressly grants appraisal rights.

Amendment to our Declaration of Trust, Dissolution and Mergers

        Under the Maryland REIT Law, a REIT formed under Maryland law generally cannot dissolve, amend its declaration of trust, convert or merge unless these actions are approved by at least two-thirds of all shares entitled to be cast on the matter. The Maryland REIT Law allows a trust's declaration of trust to set a lower percentage, so long as the percentage is not less than a majority of the votes entitled to be cast on the matter. Our declaration of trust provides for approval of any of the foregoing actions (except amendments to certain provisions of the declaration of trust) by a majority of shares entitled to vote on these actions provided the action in question has been approved by a majority of our Board of Trustees. Our declaration of trust further provides that if permitted in the future by Maryland law, the majority required to approve any of the foregoing actions (subject to such exceptions) will be the majority of shares voted. Under the Maryland REIT Law, a declaration of trust may permit the trustees by a two-thirds vote to amend the declaration of trust from time to time to qualify as a REIT under the Code or the Maryland REIT Law without the affirmative vote or written consent of the shareholders. Our declaration of trust permits this type of action by our Board of Trustees. Our declaration of trust also permits our Board of Trustees to effect changes in our unissued shares, as described more fully above, and to change our name without shareholder approval, and provides that, to the extent permitted in the future by Maryland law, our Board of Trustees may amend any other provision of our declaration of trust without shareholder approval. The Maryland REIT Law provides that a majority of our entire board, without action by the shareholders, may, among other things, amend our declaration of trust to change the name or other designation or the par value of any class or series of our shares and the aggregate par value of our shares.

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Anti-Takeover Effect of Maryland Law and of Our Declaration of Trust and Bylaws

        The following provisions in our declaration of trust and bylaws and in Maryland law could delay or prevent a change in our control:

•

the prohibition in our declaration of trust of any shareholder other than RMR LLC and its affiliates from owning more than 9.8% of the number or value of our outstanding shares;



•

the division of our Trustees into classes, with two classes remaining with terms expiring in 2016 and 2017, respectively, which could delay a change of control of us (although effective at our 2015 annual meeting of shareholders, trustees of the class of trustees whose term expired at that meeting or expires at a subsequent annual meeting of shareholders are elected annually, with all of our trustees being elected annually as of our 2017 annual meeting of shareholders, and with a majority of our current trustees having terms expiring at our 2016 annual meeting of shareholders);



•

the authority of our Board of Trustees to make various elections under Maryland's Unsolicited Takeover Act and other provisions of Maryland law which may delay or otherwise prevent a change of control of us;



•

shareholder voting rights and standards for the election of trustees and other matters which generally require larger majorities for approval of actions which are not approved by our trustees or for the election of trustees in contested elections than for actions which are approved by our trustees or for the election of trustees in uncontested elections;



•

the authority of our Board of Trustees, and not our shareholders, to adopt, amend or repeal our bylaws;



•

the ability of our trustees to expand our Board of Trustees and fill vacancies which may be created by the Board of Trustees;



•

the fact that only our Board of Trustees may call shareholder meetings and that shareholders are not entitled to act without a meeting;



•

required qualifications for an individual to serve as a trustee and a requirement that certain of our trustees be "managing trustees" and other trustees be "independent trustees";



•

limitations on the ability of, and various requirements that must be satisfied in order for, our shareholders to propose nominees for election as trustees and propose other business to be considered at a meeting of our shareholders;



•

limitations on the ability of our shareholders to remove our trustees; and



•

the authority of our Board of Trustees to adopt certain amendments to our declaration of trust without shareholder approval, including the authority to increase or decrease the number of authorized shares, to create new classes or series of shares (including a class or series of shares that could delay or prevent a transaction or a change in our control that might involve a premium for our shares or otherwise be in the best interests of our shareholders), to increase or decrease the number of shares of any class or series, and to classify or reclassify any unissued shares from time to time by setting or changing the preferences, conversion or other rights, voting powers, restrictions, limitations as to distributions, qualifications or terms or conditions of redemption of our shares or any new class or series of shares created by our Board of Trustees.

        Because of our ownership of AIC, we are an insurance holding company under applicable state law; accordingly, anyone who intends to solicit proxies for a person to serve as one of our trustees or for another proposal of business not approved by our Board of Trustees may be required to receive pre-clearance from the concerned insurance regulators.

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        In addition, our revolving credit and term loan agreements and our shareholders agreement with AIC each also contain change in control provisions, which are further described below, and our business management and property management agreements with RMR LLC contain provisions that allow for termination for convenience and termination for a performance reason but require the payment of a termination fee, as further described in those agreements.

        For all of these reasons, our shareholders may be unable to realize a change of control premium for any of our shares they own or otherwise effect a change of our policies.

Liability of Shareholders for Breach of Restrictions on Ownership

        Our revolving credit facility and term loan agreements provide that a change in our control, as defined in those agreements and including RMR LLC ceasing to act as our business manager and property manager, constitutes a default under those agreements, and a default under those agreements could result in a cross-default under our senior unsecured notes or our other debt. In addition, our shareholders agreement with respect to AIC provides that AIC and the other shareholders of AIC may have rights to acquire our interests in AIC if such an acquisition occurs or if we experience some other change in control. If a breach of the ownership limitations or other provisions of our declaration of trust or bylaws results in a default under our revolving credit facility or term loan agreements or our other debt or a loss of our ownership interests in AIC, the shareholder or shareholders causing the breach may be liable to us and may be liable to our other shareholders for damages. These damages may be in addition to the loss of beneficial ownership and voting rights of the shares owned by the breaching shareholder or shareholders, as described above, and these damages may be material.

SELLING SECURITY HOLDERS

        Selling security holders are persons or entities that, directly or indirectly, have acquired or will from time to time acquire from us, securities of the type described in this prospectus in various private transactions. These selling security holders may from time to time offer and sell the securities pursuant to this prospectus and any applicable prospectus supplement.

        Information regarding the selling security holders, where applicable, will be set forth in a prospectus supplement, in a post-effective amendment, or in filings we make with the SEC under the Exchange Act which are incorporated herein by reference.

PLAN OF DISTRIBUTION

        We or our selling security holders may sell the securities to one or more underwriters for public offering and sale by them or may sell the securities to investors directly or through agents or through a combination of any of these methods of sale. Any underwriter or agent involved in the offer and sale of the securities will be named in the applicable prospectus supplement.

        The distribution of the securities may be effected from time to time in one or more transactions at a fixed price or prices, which may be changed, at market prices prevailing at the time of sale, at prices related to the prevailing market prices or at negotiated prices. We or our selling security holders may engage in at the market offerings into an existing trading market in accordance with Rule 415(a)(4) of the Securities Act. We or our selling security holders also may, from time to time, authorize underwriters acting as their agents to offer and sell the securities upon the terms and conditions as are set forth in the applicable prospectus supplement. In connection with the sale of securities, underwriters may be deemed to have received compensation from us or our selling security holders in the form of underwriting discounts or commissions and may also receive commissions from purchasers of securities for whom they may act as agent. Underwriters may sell securities to or through dealers, and the dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for whom they may act as agent.

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        Any underwriting compensation paid by us or our selling security holders to underwriters or agents in connection with the offering of securities offered by means of this prospectus, and any discounts, concessions or commissions allowed by underwriters to participating dealers, will be set forth in the applicable prospectus supplement. Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions, under the Securities Act. Underwriters, dealers and agents may be entitled, under agreements entered into with us or our selling security holders, to indemnification against and contribution toward civil liabilities, including liabilities under the Securities Act.

        Unless otherwise specified in the applicable prospectus supplement, any securities issued hereunder (other than common shares) will be new issues of securities with no established trading market. Any underwriters or agents to or through whom such securities are sold by us or our selling security holders for public offering and sale may make a market in such securities, but such underwriters or agents will not be obligated to do so and may discontinue any market making at any time without notice. We cannot assure you as to the liquidity of the trading market for any such securities.

        We or our selling security holders may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by us or our selling security holders or borrowed from us, our selling security holders or others to settle those sales or to close out any related open borrowings of shares, and may use securities received from us or our selling security holders in settlement of those derivatives to close out any related open borrowings of shares. The third party in such sale transactions will be an underwriter and will be identified in the applicable prospectus supplement.

        From time to time, one or more of the selling security holders may pledge, hypothecate or grant a security interest in some or all of the securities owned by them. The pledgees, secured parties or persons to whom the securities have been hypothecated will, upon foreclosure in the event of default, be deemed to be selling security holders. The number of the initial selling security holder's securities offered under this prospectus will decrease as and when any pledgee, secured party or other person takes such actions. The plan of distribution for that selling security holder's securities will otherwise remain unchanged. In addition, a selling security holder may, from time to time, sell the securities short, and, in those instances, this prospectus may be delivered in connection with the short sales and the securities offered under this prospectus may be used to cover short sales.

        We will not receive any proceeds from sales of any securities by the selling security holders. We cannot assure you that the selling security holders will sell all or any portion of their securities, if any, covered by this prospectus.

        In connection with an offering of securities, the underwriters may engage in stabilizing and syndicate covering transactions. These transactions may include overallotments or short sales of the securities, which involves sales of securities in excess of the principal amount of securities to be purchased by the underwriters in an offering, which creates a short position for the underwriters. Covering transactions involve purchases of the securities in the open market after the distribution has been completed in order to cover short positions. Stabilizing transactions consist of certain bids or purchases of securities made for the purpose of preventing or retarding a decline in the market price of the securities while the offering is in progress. Any of these activities may have the effect of preventing or retarding a decline in the market price of the securities being offered. They may also cause the price of the securities being offered to be higher than the price that otherwise would exist in the open market in the absence of these transactions. The underwriters may conduct these transactions on the

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NYSE, in the over-the-counter market or otherwise. If the underwriters commence any of these transactions, they may discontinue them at any time.

        The underwriters, dealers and agents that participate in the offer of securities covered by this prospectus, or their affiliates or associates, may engage in transactions with and perform services for us or our selling security holders and our or their affiliates in the ordinary course of business for which they may have received or receive customary fees and reimbursement of expenses.

LEGAL MATTERS

        Unless otherwise specified in connection with the particular offering of any securities, Sullivan & Worcester LLP, as to certain matters of New York law, and Venable LLP, as to certain matters of Maryland law, will pass upon the validity of the offered securities for us. Sullivan & Worcester LLP has passed upon certain tax matters in an opinion filed with the registration statement of which this prospectus is a part. Sullivan & Worcester LLP also represents RMR LLC, our manager, Five Star, SIR and certain of their affiliates on various matters. Venable LLP also represents Five Star and SIR on various matters.

EXPERTS

        The consolidated financial statements of Senior Housing Properties Trust appearing in Senior Housing Properties Trust's Annual Report (Form 10-K) for the year ended December 31, 2014 (including the schedule appearing therein), and the effectiveness of Senior Housing Properties Trust's internal control over financial reporting as of December 31, 2014, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are, and audited financial statements to be included in subsequently filed documents will be, incorporated herein in reliance upon the reports of Ernst & Young LLP pertaining to such financial statements and the effectiveness of our internal control over financial reporting as of the respective dates (to the extent covered by consents filed with the Securities and Exchange Commission) given on the authority of such firm as experts in accounting and auditing.

        The combined statement of revenues and certain expenses of the CCIT—Healthcare Properties for the year ended December 31, 2014, incorporated in this prospectus by reference from the Current Report on Form 8-K filed by Senior Housing Properties Trust on June 26, 2015, has been audited by McGladrey LLP, independent auditors, as stated in their report, which is incorporated herein by reference. Such statement of revenues and certain expenses has been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

        The audited historical statement of revenues and certain expenses of the Senior Living Communities included on pages F-6 through F-9 of Senior Housing Properties Trust's Current Report on Form 8-K dated June 26, 2015 has been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, independent certified public accountants, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND MORE INFORMATION

        We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy any reports, statements or other information on file at the SEC's public reference room at 100 F Street, N.E., Washington, D.C. 20549. You can request copies of those documents upon payment of a duplicating fee to the SEC. This prospectus is part of a registration statement and does not contain all of the information set forth in the registration statement. You may call the SEC at 1-800-SEC-0330 for further information on the operation of the public reference rooms. You can review our SEC filings and the registration statement by accessing the SEC's Internet

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site at www.sec.gov or by accessing our Internet site at www.snhreit.com. Website addresses are included in this prospectus as textual references only and the information in such websites, and any information that is linked to our website (other than our filings with the SEC that are expressly incorporated by reference as set forth under "Information Incorporated by Reference"), is not incorporated by reference into this prospectus or related registration statement.

        Our common shares are traded on the NYSE under the symbol "SNH," and you can review similar information concerning us at the office of the NYSE at 20 Broad Street, New York, New York 10005.

INFORMATION INCORPORATED BY REFERENCE

        The SEC allows us to "incorporate by reference" the information we file with them, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus. Statements in this prospectus regarding the contents of any contract or other document may not be complete. You should refer to the copy of the contract or other document filed as an exhibit to the registration statement. Later information filed with the SEC will update and supersede information we have included or incorporated by reference in this prospectus.

        We incorporate by reference the documents listed below and any filings made after the date of the initial filing of the registration statement of which this prospectus is a part made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act until the offering of the securities made by this prospectus is completed or terminated (other than, in each case, documents or information deemed to have been furnished and not filed in accordance with SEC rules, including under Items 2.02 and 7.01 (and any related Item 9.01) of Form 8-K):

•

our Annual Report on Form 10-K for the fiscal year ended December 31, 2014;



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our Quarterly Report on Form 10-Q for the fiscal quarter ended March 31, 2015;



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our Current Reports on Form 8-K dated January 29, 2015, February 3, 2015, February 4, 2015, May 19, 2015, June 5, 2015 (Item 1.01 and the related exhibits included in Item 9.01 only) and June 26, 2015;



•

the information identified as incorporated by reference under Items 10, 11, 12, 13 and 14 of Part III of our Annual Report on Form 10-K for the fiscal year ended December 31, 2014, from our definitive Proxy Statement for our 2015 Annual Meeting of Shareholders dated March 2, 2015; and



•

the description of our common shares contained in our registration statement on Form 8-A dated September 21, 1999, including any amendments or reports filed for the purpose of updating that description.

        We will provide you with a copy of the information we have incorporated by reference, excluding exhibits other than those which we specifically incorporate by reference in this prospectus. You may obtain this information at no cost by writing or telephoning us at: Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts, 02458-1634, (617) 796-8234, Attention: Investor Relations.

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Table of Contents

 

Senior Housing Properties Trust

$500,000,000 4.750% Senior Notes Due 2028

PROSPECTUS SUPPLEMENT

February 8, 2018

BBVA
Mizuho Securities
RBC Capital Markets
UBS Investment Bank
Wells Fargo Securities
BofA Merrill Lynch
Citigroup
Morgan Stanley
PNC Capital Markets LLC
Regions Securities LLC
SMBC Nikko
US Bancorp
BB&T Capital Markets
BMO Capital Markets
Fifth Third Securities
FTN Financial Securities Corp
Ramirez & Co., Inc.

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