-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 Ws5h0XXmU7VapZQ9gQ50dX/xOSAp1hfcjBHZRSOLgAdxH+ZxRZvPnA2l3cEQN0J1
 j28CVs7Qub0jmrV21BzfDA==

<SEC-DOCUMENT>0001047469-08-007172.txt : 20080604
<SEC-HEADER>0001047469-08-007172.hdr.sgml : 20080604
<ACCEPTANCE-DATETIME>20080603203053
ACCESSION NUMBER:		0001047469-08-007172
CONFORMED SUBMISSION TYPE:	FWP
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20080604
DATE AS OF CHANGE:		20080603

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SENIOR HOUSING PROPERTIES TRUST
		CENTRAL INDEX KEY:			0001075415
		STANDARD INDUSTRIAL CLASSIFICATION:	REAL ESTATE INVESTMENT TRUSTS [6798]
		IRS NUMBER:				043445278
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		FWP
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	333-135716
		FILM NUMBER:		08879010

	BUSINESS ADDRESS:	
		STREET 1:		400 CENTRE STREET
		CITY:			NEWTON
		STATE:			MA
		ZIP:			02458
		BUSINESS PHONE:		6173323990

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SENIOR HOUSING PROPERTIES TRUST
		CENTRAL INDEX KEY:			0001075415
		STANDARD INDUSTRIAL CLASSIFICATION:	REAL ESTATE INVESTMENT TRUSTS [6798]
		IRS NUMBER:				043445278
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		FWP

	BUSINESS ADDRESS:	
		STREET 1:		400 CENTRE STREET
		CITY:			NEWTON
		STATE:			MA
		ZIP:			02458
		BUSINESS PHONE:		6173323990
</SEC-HEADER>
<DOCUMENT>
<TYPE>FWP
<SEQUENCE>1
<FILENAME>a2186152zfwp.htm
<DESCRIPTION>FWP
<TEXT>
<HTML>
<HEAD>
</HEAD>
<BODY BGCOLOR="#FFFFFF" LINK=BLUE  VLINK=PURPLE>
<BR>
<FONT SIZE=3 ><A HREF="#08ZBX10503_1">QuickLinks</A></FONT>
<font size=3> -- Click here to rapidly navigate through this document</font>
<P ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>


<!-- COMMAND=ADD_BASECOLOR,"Black" -->




<!-- COMMAND=ADD_DEFAULTFONT,"font-family:times;" -->


 </FONT></P>

<!-- TOC_END -->
<P ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>
ISSUER FREE WRITING PROSPECTUS<BR>
(SUPPLEMENTING PRELIMINARY PROSPECTUS<BR>
SUPPLEMENT DATED JUNE 2, 2008 AND<BR>
ACCOMPANYING PROSPECTUS DATED<BR>
JULY 12, 2006)<BR>
FILED PURSUANT TO RULE 433<BR>
REGISTRATION STATEMENT NO. 333-135716 </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="de10503_senior_housing_properties_trus__sen03094"> </A>
<A NAME="toc_de10503_1"> </A>
<BR></FONT><FONT SIZE=2><B>Senior Housing Properties Trust<BR>  Issuer Free Writing Prospectus Dated June&nbsp;3, 2008    <BR>    </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The information in this Issuer Free Writing Prospectus supplements, and should be considered in connection with, the information contained in the Preliminary
Prospectus Supplement dated June&nbsp;2, 2008 and the accompanying Prospectus dated July&nbsp;12, 2006, or the preliminary prospectus, of Senior Housing Properties Trust, or Senior Housing. The
following information assumes no exercise of the underwriter's over-allotment option. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Total shares offered:</B></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The Senior Housing offering has been increased from 10,000,000 common shares of beneficial interest to
17,000,000 common shares of beneficial interest. In addition, the underwriters have been granted an over-allotment option for 2,550,000 common shares of beneficial interest. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Public offering price:</B></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The public offering price is $21.09 per share. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Last reported sale price of common shares on the New York Stock Exchange on June&nbsp;3, 2008:</B></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;$21.09 per share. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Proceeds to Senior Housing:</B></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Net proceeds to Senior Housing from the offering, after deducting underwriting discounts and
commissions and estimated offering expenses, are estimated to be approximately $342.1&nbsp;million, instead of approximately $211.9&nbsp;million as originally reflected in the preliminary
prospectus. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Common shares outstanding after the offering:</B></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Senior Housing shares outstanding after the offering will be approximately
111,938,558 shares, instead of 104,938,558 shares as originally reflected in the preliminary prospectus. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Use of proceeds:</B></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Senior Housing intends to use the net proceeds to repay borrowings under its revolving credit facility and
for general business purposes, including funding in part pending acquisitions or possible future acquisitions of properties. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Increase in authorized shares:</B></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;On June&nbsp;3, 2008, Senior Housing amended its declaration of trust, increasing the number
of its authorized shares of beneficial interest from 100,000,000 to 150,000,000. Senior Housing's authorized shares are currently classified as follows: (i)&nbsp;149,700,000 common shares, $0.01 par
value per share; and (ii)&nbsp;300,000 junior participating preferred shares, $0.01 par value per share. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Settlement date:</B></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The closing of the offering is expected to occur on June&nbsp;6, 2008. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the
prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free
by visiting EDGAR on the SEC Web site at www.sec.gov. Alternatively, the issuer, any underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it
by calling UBS Investment Bank at 888-827-7275, Merrill Lynch&nbsp;&amp;&nbsp;Co. at 866-500-5408 or Morgan Stanley at
866-718-1649. </FONT></P>

<HR NOSHADE>
<P style='font-family:times;page-break-before:always'></p>
<!-- ZEQ.=1,SEQ=1,EFW="2186152",CP="SENIOR HOUSING PROPERTIES TRUST",DN="1",CHK=178227,FOLIO='blank',FILE='DISK106:[08ZBX3.08ZBX10503]DE10503A.;2',USER='BSKELLE',CD=';3-JUN-2008;18:21' -->
<!-- THIS IS THE END OF A COMPOSITION COMPONENT -->
<BR>
<P><br><A NAME="08ZBX10503_1">QuickLinks</A><br></P><!-- TOC_BEGIN -->
<FONT SIZE=2 style="font-family:times;"><A HREF="#toc_de10503_1">Senior Housing Properties Trust Issuer Free Writing Prospectus Dated June 3, 2008</A></FONT><BR>
<!-- SEQ=,FILE='QUICKLINK',USER=HYUNG,SEQ=,EFW="2186152",CP="SENIOR HOUSING PROPERTIES TRUST",DN="1" -->
<!-- TOCEXISTFLAG -->
</BODY>
</HTML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----
