RTRFIT Imrovements aking Homes - Home Innovation Labs/media/Files/ToolBase/BracingHil… · located...

Februar y 2012 Working Draf t w w w.toolbase.org

RETROFIT Improvements MakingHomesSafer inDisasters

Hazards

Purpose•Tofix/strengthencripplewallsandpoorfoundationconnections

•Topreventabuildingfromslidingoffitsfoundationduringaseismicevent

Benefits•Ensuressafetytooccupantsandproperty

IllustrationRetrofit

SummaryForensicinvestigationindicatesthatpartialorcompletecollapseofhillsidehousesisacommoncalamitywhenearthquakeshit.Themostatriskhouseshavetheentryfloorlocatedatornearstreetlevelandtallwoodlight-framewallsprovidingsupportatthehillsideedgeofthefloor.Thesehomesmayhavea“walk-out”basement.Referredtoasdown-slopehouses,thelargestlevelissupportedbyadiscontinuousfoundationthat“flows”withthegradewhichslopesdownandout.Thestructurebetweenthefoundationandthemainlevelofthehouse,astypicallyconstructed,providesapoorinterconnectionthatissusceptibletoshaking.Wallsatthesidesofdown-slopehousesarealsoirregularlyshapedastheyare“stepping”downthehillside.Thesecripplewalls,andthefactthatthemainfloorisusuallypinnedtoanupperandlowerfoundation(whicharedisconnected),providemanypivotpointsfromwhichtherigidfloorsystemmayshakeoutofplaneandcausefailuresoftheelementsthatsupportit.Retrofittingdownslopehousesisajobthatrequiresanengineereddesignandspecialtycontractor.Asaresult,thecostofthisretrofitwillvarywiththescopeoftheproject.

Bracing of Hillside HomesFloodWind Rain Seismic SnowFireRetrofit Opportunity

•Seismicretrofitsofthisscopearefiniteprojectsinandofthemselves(specialtycontractorsexisttoservethismarket)

Detail of shear wall construction and anchorage at stepped foundation

Februar y 2012 Working Draf t w w w.toolbase.org

Photo:www.fema.gov

Potential Damage

Key Steps •Hireaprofessionalinspectortodeterminethescopeofaretrofit.•Generallyspeaking,thisretrofitwillincorporateprimaryandsecondaryanchoringofthemainfloorsystemandloadpathreinforcementcomponents.

•Yourcontractormayhaveadditionalideasonhowtoimprovethesafetyofyourhome.•Formoredetailsaboutthisretrofitimprovement,pleaserefertothelistofResourcesinthesectionbelow.

ResourcesFEMA,Earthquake Safety Guide for Homeowners http://www.fema.gov/library/viewRecord.do?fromSearch=fromsearch&id=1449FEMA,Homebuilders’ Guide to Earthquake-Resistant Design and Construction http://www.fema.gov/library/viewRecord.do?id=2103