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This document was prepared by
URS Group, Inc.200 Orchard Ridge Drive, Suite 101Gaithersburg, MD 20878
Acknowledgements
Federal Emergency Management Agency (FEMA)
L. Gina White, FEMA Region IV, Mitigation, Project Monitor
David Kennard, FEMA Region IX, Mitigation
Daniel Powell, FEMA Region IX, Mitigation
Dennis Tewksbury, FEMA Region I, Mitigation
Christopher Hudson, FEMA HQ, Mitigation
State of California
Ernylee Chamblee, California Department of Forestry and Fire Protection
Greg Griswold, California Department of Forestry and Fire Protection (San Diego Unit)
Tom O’Keefe, California Department of Forestry and Fire Protection (San Bernardino Unit)
Ken Worman, Governor’s Office of Emergency Services
Local California Officials
Cliff Hunter, Rancho Santa Fe Fire Protection District
Clay Westling, City of San Diego
Bill Metcalf, North County Fire District
Technical Assistance Contractor Team
Christopher M. Barkley, PE, URS Group, Inc., Task Order Coordinator
Diana Burke, ELS, URS Group, Inc.
Sherry Crouch, PE, URS Group, Inc.
Michael Gayrard, URS Group, Inc.
Rich Schell, RPF #1978, RWS Consulting
Thomas L. Smith, AIA, TLSmith Consulting, Inc.
Chris White, Anchor Point Group
Cover photo: Anchor Point Group, Boulder, CO
FS No. 1 – Wildland/Urban Interface Construction HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of5
Wildland/Urban Interface Construction Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 1
Purpose Toprovideinformationaboutwildfirebehaviorandrecommendationsforbuildingdesignandconstructionmethodsinthewildland/urbaninterface.Implementationoftherecommendeddesignandconstructionmethodscangreatlyincreasethechancesofabuilding’ssurvivalinawildfire(seeFigure1).
BackgroundWildfiresareacommon,natural,andessentialoccurrenceintheforests,woodlands,brushlands,andgrasslandsoftheUnitedStates.Whenconditionsareacceptable,fireprofessionalsusefiretorevitalizetheecosystemandreduceaccumulatedvegetationthatcanfuelawildfireundercertainconditions.
Althoughtheseverityandtimingoffireseasonsvarywidelyfromregiontoregion,wildfiresoftenposeathreattolives,property,andresources.Duringanaveragefireseason,hundredsofhomesaredamagedordestroyedbywildfire,andinextremefireconditions,thousandsofhomescanbedamagedordestroyed.Severefireweatherinareaswithsignificantamountsofwildlandfuelscanleadtoextremefirebehavior.
WildlandfuelsvarythroughouttheUnitedStates.InthePacificnorthwestandtheLakeStates,forestsarethepredominatewildlandfuel.InsouthernCalifornia,chaparralbrushpredominates.Theplainsstateshavegrassandoakwoodlands,NewJerseyhasPineBarrens,andthesoutheasthaspineandhardwoodforests.
Figure 1. Ahomeinthewildland/urbaninterfacethatsurvivedawildfire(AnchorPointGroup,Boulder,CO).
Page2of5 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 1 – Wildland/Urban Interface Construction
Wildfirescandamagebuildingsthroughdirectflamecontact,convection(heatthatrisesfromafireandcreatesasmokecolumn),conduction(heatthattransfersthroughmaterialsuchasmetalroofsandrailings),andradiation(heatfromafirenexttothebuilding).Wildfirescanalsocreateburningembersthatriseinthesmokecolumnandfallonbuildings.Firebrands(largepiecesofwind-driven,burningmaterial)canbeblownthroughwindowsorlodgedagainstabuildingandleadtoignitionofthebuilding.
Traditionaleffortstoprotectbuildingsfromwildfireshavefocusedonfightingthefirebeforeitreachesthebuildings.Withtheexpansionofresidentialconstructionintopreviouslyundevelopedforestsandwildlands,morebuildingsarenowatriskfromwildfires.Fightingorsuppressingthefireisoftendifficultorimpractical;buildingsmustthereforealsobeconstructedtobefire-resistant.Nobuildingcanbecompletelyfireproof,butimplementingtherecommendationsthataredescribedintheseFactSheetsshouldgreatlyreducethepotentialfordamagetoabuildingandgreatlyincreaseitschanceofsurvival.
Construction in the Wildland/Urban InterfaceThefollowingfactorsaffecttheprobabilitythatabuildingwillsurviveawildfire:Topographyandweather•Defensiblespace•Buildingenvelope•Communityinfrastructure•
Topography and WeatherWildfiresgenerallyfolloworaredrivenbyterrainandweather.Buildingsatthetopofacanyonorridgeline,atmid-slope,orinaravinehaveahigherriskfordamagefromawildfireduetotheinteractionofthesefeatureswithstrongwindsthanatlocationssuchasvalleybottoms.Whenaconstructionsiteisselected,thetopographicfeaturesonandsurroundingasiteshouldbeevaluatedfortheirpotentialcontributiontotheexposureofabuildingtoawildfire.Abuilding’sconfigurationandlocationonasiteshouldbepredicatedonminimizingtheriskfromthesetopographicfeatures.
SeeFactSheet#3,SelectingtheConstructionSite.
Defensible Space Wildfirestravelquicklyinareaswherevegetationisdryandabundant.Adefensiblespacearoundabuildingcanimprovetheprobabilitythatthebuildingwillsurviveawildfire.Adefensiblespaceisanareawherecombustiblematerial,includingvegetation,hasbeentreated,clearedormodifiedtoslowtherateandintensityofanadvancingwildfireandtocreateasaferareaforfire-suppressionoperationstooccur.Buildingssurroundedbyzonesofnon-vegetatedareasorareaspopulatedbyfire-resistantvegetationaremorelikelytosurvive.
SeeFactSheet#4,DefensibleSpace.
FS No. 1 – Wildland/Urban Interface Construction HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of5
Building Envelope Duringawildfire,combustibleexteriorbuildingcomponentssuchasroofcoverings,siding,anddeckscanignite,leadingtoseveredamagetoortotallossofthebuilding.Therefore,theuseofnoncombustibleorfire-resistantmaterialsshouldbeconsideredforexteriorcomponents.Figure2showsthecomponentsofthebuildingenvelope.
Alsocriticalistheconfigurationofthenoncombustibleorfire-resistantmaterials.Unlessconstructionmeasuresthatprovideprotectionfromawildfireareimplemented,heatandemberscanpenetratethebuildingenvelopeatvents,unsealedmechanicalorelectricalopenings,andthroughwindowsbrokenbyheatorwind-blownfirebrands.Whentheseopeningsarepenetrated,thebuildingcanburnfromtheinsideout.
Iftheenvelopehasbeendesignedandconstructedtobefire-resistant,boththeexteriorandinteriorofthebuildingwillbemorecapableofresistingawildfirelongenoughforthedangertopassorforfirefighterstoarrive.
SeeFactSheets#5through#16.
Community InfrastructureAhomethathasbeenconstructedtobefire-resistantandhasadefensiblespacemaynotbesufficienttopreventdamagefromawildfire.Survivingawildfiremayalsodependoninfrastructuresuchaslocalwaterresourcesforfirefightingandroadsthataredesignedforemergencyvehicleaccess.Thebuildingsiteshouldalsohaveadequateinfrastructuretoensureaccessforfirefightingcrews.
SeeFactSheet#17,CommunityInfrastructure.
Figure 2. Thebuildingenvelope.
Building Envelope
Vents
Garage door Exterior door
Siding
Roof Deck
Fence
Windows
Eaves
Foundation
Gutters
Page4of5 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 1 – Wildland/Urban Interface Construction
Prioritizing Fire-resistant Construction TechniquesTheriskofwildfirevariesgreatlyanddependsonlocalfuels,weather,andtopography.Theriskatabuildingsitemustbedeterminedbeforetheappropriatedesignandconstructionmethodsforaneworexistingbuildingcanbeselectedandthemeasurescanbeprioritized.
Hazard and Risk AssessmentsThefoundationofanaccuratehazardandriskassessmentisinformationonwildfirefuels,weather,topography,assetsatrisk,andtheprobabilityofawildfireoccurrence.Asitecanbeinanareawithaveryhighhazard(highlyvulnerabletowildfire)buthavealowriskofwildfire,suchasasiteatahighaltitude.ThisinformationcanbeusedtodesignateFireSeverityZones.Thezonescanthenbegivenarating,fromlowtoextreme,asshowninFigure3.
Ahazardandriskassessmentcanhelpdeterminethelevelofmitigationthatisneededforabuilding.Theassessment,whichcanbeconductedataregional,state,orlocallevel,needstobebothcredibleandprofessionaltoensurethattheanalysisisaccurate,comprehensive,andverifiable.Someregional,state,andlocalagenciesproducehazardriskmapssimilartothoseshowninFigures3and4.Thesemapsmaybefoundinstate,tribal,andlocalagencyhazardmitigationplansthathavebeenapprovedbytheFederalEmergencyManagementAgency(FEMA).
New BuildingsFornewconstruction,FEMArecommendsfollowingthedesignandconstructionguidanceprovidedinthisseriesofFactSheets.
Existing BuildingsFEMArecognizesthatitmaynotbefinanciallypossibleforthehomeownertoimplementallofthemeasuresthatarerecommendedinthisseriesofFactSheets.FEMArecommendsthathomeownersconsultwithlocalfireandbuildingcodeofficialsorotherfiremanagementspecialiststoperformavulnerabilityassessmentanddevelopacustomized,prioritizedlistofrecommendationsforremedialworkondefensiblespaceandthebuildingenvelope.
Helpfulinformationaboutthevulnerabilitiesofthebuildingenvelopeisavailableathttp://firecenter.berkeley.edu/default.htm.TheHomeowner’sWildfireAssessmentsurveyonthis
Figure 3. Exampleofafirehazardratingmap.Firehazardratingscanhelpdeterminethelevelofmitigationthatisnecessaryforwildfiremanagement(AnchorPointGroup,Boulder,CO).
FS No. 1 – Wildland/Urban Interface Construction HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page5of5
websiteisahelpfultoolthatpropertyownerscanusetolearnaboutthespecificrisksaparticularbuildinghasandthemeasuresthatcanbetakentoaddressthem.
Construction StandardsManycommunitiesenforceregulationsregardingwhereandhowbuildingsmaybesited,designed,andconstructed.Theregulations,however,refertominimumstandards.Individualpropertyownershavetheoptiontoexceedthesestandards,anddoingsoveryoftenincreasestheprobabilitythatthehomewillsurviveawildfire.
ResourcesCenterforFireResearchandOutreach.UniversityofCalifornia,Berkeley:CollegeofNatural
Resources.http://firecenter.berkeley.edu/default.htm.
Christman,L.2008.Trial by Fire: Can Your Home Take the Heat? Redding.com:Home&Garden.http://www.redding.com/news/2008/Feb/16/trial-fire-can-your-home-take-heat/.
Underwood,J.1995.“Fire-ResistantDetails.”Fine Homebuilding96:90–93.http://www.taunton.com/finehomebuilding/how-to/articles/fire-resistant-details.aspx.
Figure 4. Exampleofafuelmodelmap.Fuelmodelsthatdemonstratethelocationofcombustiblevegetationarepartofthefoundationforfirebehaviorcalculations(AnchorPointGroup,Boulder,CO).
FS No. 2 – Summary of Recommendations HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of5
Summary of Wildfire Construction Recommendations Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 2
Stateandlocalcodesshouldincluderequirementsforwildfiremitigationforbothnewconstructionandupgradestoexistingbuildingsinwildfirezones.Inareaswherebuildingsareparticularlyvulnerabletotheriskofwildfire,implementingmeasuresthatexceedthecodescanimprovetheprobabilitythatabuildingwillsurviveawildfire.
TheUnified Hazard Mitigation Assistance GuidanceandtheWildfire Mitigation PolicyfortheHazardMitigationGrantProgram(HMGP)andPre-DisasterMitigation(PDM)ProgramprovideinformationonwhichactivitiesareconsideredeligibleforfundingbytheFederalEmergencyManagementAgency(FEMA)forwildfiremitigationactivities.
ThisseriesofTechnicalFactSheetsfromFEMAprovideinformationabouthowtominimizethepotentialfordamagetoordestructionofbuildingsinwildfirezonesfromwildfires.Theinformationpertainstobothnewandexistingbuildings.
TheFactSheetsareavailableontheFEMAwebsite(www.fema.gov)asAdobePortableDocumentFormat(PDF)files.YoumusthaveAdobeReadertoviewthePDFfiles.ThelatestversionofAdobeReaderisrecommendedandcanbedownloadedfromwww.adobe.com.
ThefollowingisasummaryoftherecommendationscontainedinFactSheets#3through#17.
Fact Sheet #3: Selecting the Construction Site
Topographicfeaturessuchasslopesandcanyons,localvegetation,andweathercangreatlyinfluencewildfirebehavior.Homebuildersshouldconsiderthesefactorscarefullywhenselectingaconstructionsite
Page2of5 09/08 HomeBuilder’sGuidetoConstructioninWildfireZone FS No. 2 – Summary of Recommendations
Fact Sheet #5: Roofs
Ofthecomponentsofthebuildingenvelope,theroofisthemostvulnerableinawildfirebecauseofitssizeandorientation.Theprobabilitythatahomewillsurviveawildfireisgreatlyinfluencedbythecomponentsoftheroofassembly.ClassAratedroofassemblieswithnoncombustiblecoveringsarerecommended.
Fact Sheet #6: Eaves, Overhangs, and Soffits
Windborneembersandconvectiveandradiantheatcanbetrappedneareavesandsoffits,whichcanigniteifnotconstructedofnoncombustibleorfire-resistantmaterials.Eaveswithshortoverhangsandflatsoffitswithaminimumofa1-hourfire-resistanceratingarerecommended.
Fact Sheet #7: Exterior Walls
Howwellexteriorwallsareabletoresistawildfiredependslargelyonthematerialsusedtoconstructthewall.Exteriorwallcoveringsthatarenoncombustibleorfire-resistantandnotsusceptibletomeltingarerecommended.Aminimumfire-resistanceratingof1hourforthewallassemblyisrecommended
Fact Sheet #4: Defensible Space
Creatingadefensiblespace,whichcanoftenbedonebythehomeowner,isrecommended.Adefensiblespaceisanareaaroundahomeinwhichvegetation,debris,andothertypesofcombustiblefuelshavebeentreated,cleared,orreduced.Landscapemanagementcreatesabarrierbetweenahomeandawildfire.Withoutadefensiblespace,firefightersmaynotattempttoprotectthehomebecausedoingsowouldbetoohazardous.
FS No. 2 – Summary of Recommendations HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of5
Fact Sheet #9: Gutters and Downspouts
Combustibledebrissuchasleavesandpineneedlescanbecometrappedingutters.Thedebriscanbeignitedbyflyingembersorfirebrandsduringawildfire,andthefirecanspreadtotheroof.Noncombustibleleafguardsoverguttersandguttersconstructedofnoncombustiblematerialsarerecommended.
Fact Sheet #10: Windows and Skylights
Flames,firebrands,radiantheat,andfailedframescancauseglazingtobreakorotherwisefail.Glazing(glass,plastic,ortranslucentmaterial)thatfailsallowseasypassageofembersandhotgasesintotheinteriorofabuilding.Insulatedglazingunitsarerecommended.Thefireratingofwindowassembliesshouldbecommensuratewiththefireratingofthewall.
Fact Sheet #11: Exterior Doors
Combustibledoorsandframescanbeignitedinawildfire,andopeningsbetweenthedoorandframeandglassinthedoorcanbepenetratedbyflames,hotgases,orembers.Thefireratingofthedoorshouldbecommensuratewiththefireratingofthewall.Weatherstrippingandnoncombustibleorfire-resistanttrimarerecommended.
Fact Sheet #8: Vents
Embersandhotgasescanbeblownorpulledintoventopeningsandenteratticspaces,crawlspaces,andductwork,leadingtoignitionoftheinteriorofthebuilding.Ventsthatareaminimumof10feetfrompropertylinesandotherbuildings,constructedofmetalproducts,andhavecorrosive-resistantmetalmeshscreensarerecommended.
Page4of5 09/08 HomeBuilder’sGuidetoConstructioninWildfireZone FS No. 2 – Summary of Recommendations
Fact Sheet #14: Landscape Fences and Walls
Onceignited,afenceconstructedofcombustiblematerialsthatisattachedtoornearabuildingcanignitethebuilding.Fencesandwallsconstructedofnoncombustiblematerialssuchasconcrete,stone,andmasonryarerecommended.Attachingafenceorwalltothebuildingshouldbeavoidedunlessthefenceorwallisconstructedofnoncombustiblematerials
Fact Sheet #15: Fire Sprinklers
Theinteriorofabuildingcanignitefromawildfireevenwhentheexteriordoesnot.Interiorandexteriorfiresprinklerscanpreventsubstantialdamagetothebuilding,protectnearbybuildings,andpreventthefirefromignitingnearbycombustiblevegetation.
Fact Sheet #13: Decks and Other Attached Structures
Embers,firebrands,andhotgasescanbecometrappedunderdecksandotherattachedstructures.Decksconstructedofheavytimberornoncombustiblematerialsarerecommended.Isolatingtheattachedstructurebysurroundingitwithnoncombustiblematerialsuchasgravel,brick,andconcretepavers,andenclosingtheundersideofthedeckwithfire-resistantskirtingarealsorecommended.
Fact Sheet #12: Foundations
Embers,firebrands,andhotgasescanignitecombustiblefoundationwallsandpenetratecrawlspaceventsandbreachedbasementwindows.Walls,vents,andwindowsinclosedfoundationsshouldbeconstructedinaccordancewiththeguidanceintheseFactSheets.Inhomeswithopenfoundations,protectingtheundersideofthefloorstructurewithfire-resistantmaterialsisrecommended.
FS No. 2 – Summary of Recommendations HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page5of5
Fact Sheet #17: Community Infrastructure
Accessroadsanddrivewaysthatarewideandstrongenoughtoaccommodateemergencyvehiclesandprovideaccessforfirefightingeffortsarenecessary.Waterresourcesforwildfiresuppressionmustbeaccessible.Roadsandwatersourcesshouldbewellmarkedonsignsconstructedoffire-resistantmaterialsforeaseofusebyemergencyresponsepersonnel.
Fact Sheet #16: Utilities and Exterior Equipment
Mostutilitiesrequirepenetrationofthebuilding’senvelopeforductingandconduit.Utilityconnectionsshouldbeinstalledunderground,ifpossible,andgapsandpenetrationsinexteriorwallsandroofsshouldbesealedwithfire-resistantproducts.Fuelshouldbestoredundergroundorsurroundedbyanoncombustiblebarrier.
FS No. 3 – Selecting the Construction Site HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of4
Selecting the Construction Site Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 3
PurposeTohelppropertyownerswhoplantobuildhomesorotherstructuresinwildfirezonesunderstandtherelationshipbetweenwildfirebehaviorandfuels,weather,andtopographysotheycanselectconstructionsitesthatminimizethepotentialfordamagefromwildfires.TheguidancelistedinthisFactSheetappliesonlytonewbuildings.
Key IssuesWildfiresspreadmorequicklyonupslopedterrainthan•onlevelterrain(seeFigure1).Topographicfeaturessuchasslopes,saddles,ridges,andcanyonscanthereforeinfluencewildfirebehavior(seebelowforadescriptionofthesefeatures).Theinteractionofwindandradiantheatwithsomeofthefeaturesisalsoanimportantfactorinwildfirebehavior.Thedirectionaslopefacesinfluencesthegrowthof•vegetation,andvegetationinfluenceswildfirebehaviorbecauseitprovidesfuelforthewildfire.Implementingthefire-mitigationmeasuresdescribedin•theotherFactSheetscannotentirelyoffsetthepotentialfordamagefromawildfireathigh-risksiteswithtopographicandvegetationfeaturesthatcancontributetoextremefirebehavior.
Topography Sloped terrain. • Wind-drivenwildfiresfollowwinddirectionandareminimallyinfluencedbytopography.Intheabsenceofastrongwind,wildfirefollowstopography,burningprimarilyupslopeandup-canyon.Wildfiresspreadupslopequicklybecauseheatrisesandpreheatsandignitesfuelssuchasbuildingsandvegetation.Saddles.• Whereavalleycrossesaridge,asaddleiscreatedbetweentwopeaks(seeFigure2).Saddlesactaswindfunnelsandareoneofthemosthazardouslocationsforhomesintermsofwildfire.
Figure 1.Firespreadsmorequicklyonupslopedterrainthanonlevelterrain.
Fuel,topography,andweatherarethethreeprincipalenvironmentalelementsthataffectwildfirebehavior.Fuels(vegetation)andlocaltopographyshouldbeconsideredwhenchoosingasiteforahometoincreasethechancethehomewillsurviveawildfire.
Page2of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 3 – Selecting the Construction Site
Ridgetops and hilltops.• Wind speeds on ridgetopsandhilltopscanbeunpredictablebuttendtobehigherthanthoseinthesurroundinglowerareasbecauseofthehigherelevationandbecausewindspeedincreasesasitflowsoverabruptchangesintopography.Buildingsintheselocationscanhave360-degreedownhillexposuretowildfire.Canyons. • Awildfireatthebottomofavegetatedcanyoncanleadtoextremelyhazardousconditionsupslope.Acanyonactslikeachimney,collectinghotgasesanddirectingsuperheatedconvectionandradiantheatupslope.Canyonsfunnelwinds(seeFigure3)thatcanfanafireandleadtoextremefirebehavior(rapidspreadofthewildfireandignitionofanentirearea).Anentirecanyoncanpre-heatfromrisinghotairandgasesandexplodeinflames,creatingafirestorm.
VegetationVegetationactsasafuelforwildfires.Vegetationbothonandadjacenttoasitecanaffect•theprobabilityofdamagetoabuildingfromawildfire.Characteristicsofvegetationsuchasdensity,continuity,andtypecaninfluencewildfirebehavior(seeFactSheet#4,DefensibleSpace,formoreinformation).South-andwest-facingslopesgenerallyretainlessmoisture,producelessvegetation,and•dryoutearlierintheyearthannorth-andeast-facingslopes.Firesondryerslopestendtoignitemoreeasily,travelmorerapidly,andburnoutfasteraslightfuelsareconsumed.Themoreheavilyvegetatedmoistslopeshavealowerpotentialforignitionbutcansustainamoreintensefireoflongerdurationthandryslopes.
Guidance Byunderstandinghowtopographyandvegetationcaninfluencewildfirebehavior,propertyownerscanselectconstructionsitesinwildfirezonesthatreducethepotentialfordamagetoabuildingfromawildfire.Followingtheguidancelistedbelowcanincreasetheprobabilitythatabuildingwillsurviveawildfire.Avoidselectingaconstructionsitealongagullyorinanarrowcanyon.•Avoidselectingaconstructionsiteinoradjacenttoasaddleornarrowmountainpass.•Avoidconstructingahomeadjacenttooronasteepslope.Ifaridgetopsiteisselected,choose•
Figure 2. Windbehavioroverasaddle.
Figure 3.Windbehaviorthroughacanyon.
FS No. 3 – Selecting the Construction Site HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of4
anareathatallowsforaminimum50-footsetbackfromwildlandvegetationonthedownslopeside(seeFigure4).Increasethesetbackatsiteswithheavierfuelssuchasinaforestedenvironment.ImplementthemeasuresinFactSheet#4,DefensibleSpace;FactSheet#12,Foundations;andFactSheet#13,Decks.Orientthenarrowestwallofthe•buildingtowardthelikelypathofawildfiretominimizetheriskofstructuralignition.Orientthebuildingbasedonwindandfuelssothatdebris,embers,andfirebrandsdonotaccumulatenexttothebuilding’swalls,especiallyneartheinsidecornersofentriesandotheroff-setwalls.Minimizethenumberofwindowsonthesideofthebuildingfacingthelikelypathofawildfire•toreducetheriskofradiantheatorfirebrandsandflyingdebrisbreakingthewindows,allowingthefiretoenterthebuilding.
ConsiderationsConsiderthevegetationcharacteristicsonandadjacenttothesiteincludingdensity,continuity,•andtype.Ifthesitehasheavy,continuousvegetation,avegetationmanagementplanmaybeneededtoreducethehazard.Creatingadefensiblespacecanenhancefireresistance(seeFactSheet#4,DefensibleSpace).Consideraccesstothehome.Steepdrivewaysandnarrowroadscanlimitaccessibilitybyfire-•fightingequipment(seeFactSheet#17,CommunityInfrastructure).Evaluatethevulnerabilitytofireofneighboringproperties.Iftheneighboringpropertieshave•firehazardsbuttheneighborsareunwillingtocooperateindevelopingamutualdefensiblespace,considerthatinformationinselectingfire-resistancemeasuresforthebuilding.
EffectivenessTheeffectivenessoftherecommendedmeasurescanvarysignificantly,dependingontheinteractionoffuels,weather,topography,andwildfirebehavior.
ResourcesBarkley,Y.C.,C.Schnepf,andJ.Cohen.2005.Protecting and Landscaping Homes in the
Wildland/Urban Interface.StationBulletin#67.Moscow,Idaho:IdahoForest,WildlifeandRangeExperimentStation.www.treesearch.fs.fed.us/pubs/22257.
CaliforniaDepartmentofForestryandFireProtection.www.fire.ca.gov.
CaliforniaFireSafeCouncil.www.firesafecouncil.org.
Figure 4.Exampleofsetbackfromwildlandvegetation.
50 feet
Page4of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 3 – Selecting the Construction Site
FirewiseCommunitiesProgram.www.firewise.org/newsroom/faq.htm.
NationalWildfireCoordinatingGroup.www.nwcg.gov.
Slack,P.2000.Firewise Construction Design and Materials.ColoradoStateForestService.
FS No. 4 – Defensible Space HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of4
Defensible Space Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 4
PurposeToprovideinformationaboutcreatingadefensiblespacetoreducethepotentialfordamagetohomesfromwildfires.Guidancepertainstobothnewandexistingbuildings.
BackgroundAdefensiblespaceisanareaaroundabuildinginwhichvegetation,debris,andothertypesofcombustiblefuelshavebeentreated,cleared,orreducedtoslowthespreadoffiretoandfromthebuilding.Informationaboutlocalvegetation,weather,andtopographyisusedtodeterminetheFireSeverityZoneofanarea,whichcanhelpdeterminethemosteffectivedesignofadefensiblespace.
Adefensiblespaceisoneofthemostcost-effectivewaystoprotectabuildingfromawildfireandcanoftenbecreatedbythepropertyowner.
Key Issues Wildlandvegetationsuchasgrass,brush,andtimbercanbeextremelycombustible.The•vegetationcanburnwithgreatintensityandproducefirebrandsandburningembersthatcanbecomewind-drivenhazards.Landscapevegetationcanbeascombustibleaswildlandvegetation.•Combustibleplantshavethesecharacteristics:•
Volatileresinsandoils(generallyaromatic –whencrushed)
Narrowleavesorlong,thinneedlessuchas –coniferneedles
Waxyorfuzzyleaves –
Anaccumulationofdeadleavesandtwigson –andundertheplant
Looseorpaperybark –
Awildfirecanmovehorizontallyfromshrubto•shrubandtreetotree.Awildfirecanalsotravelverticallyfromthegroundupintothetreetops,resultingina•catastrophiccrownfire(afirethatcantravelatanincrediblepacethroughthetopofaforest).Figure1showsafirethatisspreadingverticallyfromgrassestoshrubstolowbranches.Accessorybuildingsandstructuresandotheritemscommonlyfoundinyardsthataremade•
Figure 1.Firespreadsverticallythroughvegetation(AnchorPointGroup,Boulder,CO).
Page2of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 4 – Defensible Space
ofcombustiblematerialscanalsoputanotherwisefire-resistantbuildingatriskofignitionanddestruction.Combustiblevegetationandmaterialsarounda•building(seeFigure2)can:
– Increasetheriskofbuildingignition
Restrictthespacenecessarytoprovide –firefightersarelativelysafeplacetoprotectabuilding
Increasethechancethatabuildingonfire –willigniteadjacentwildlands
GuidanceAssessboththehorizontalandverticalaspectsofvegetationwhendesigningthedefensible•space.Topreventthehorizontalspreadofwildfire,thinshrubsandtreessothecrownsdonot•intersectandthereisspacebetweenindividualshrubsandtrees.Topreventtheverticalspreadofwildfire,keepthelowesttreebranchesprunedandtrimmed•tomaintainverticalseparationfromthetopofshrubsandgrassestothelowesttreebranches.Theverticaldistanceneededwillvarysignificantly,dependingonthespeciesoftreeandcompositionoftheunderstory.Createthreeconcentriczonesaroundthebuilding(seeFigure3).Zone1,thezoneclosest•tothebuilding,normallyhasthegreatestneedforfuelmodificationwithprogressivelylessmodificationintheothertwozones.ThehighertheFireSeverityZone,thelargertheconcentriczonesshouldbe.Consultthelocalorstatefireagencyforassistance.Thethreezonesarediscussedfurtherbelow.
Zone 1EliminateallcombustiblematerialsinZone1(within30feetofthehome)suchasfire-prone•vegetation,firewoodstacks,combustiblepatiofurniture,umbrellas,anddimensionedlumberdecking(seeFigure4).Desirablesubstitutionsincludeirrigatedgrass,rockgardens,stonepatios,metalpatiofurniture,andnoncombustibledecking(seeFactSheet#13,DecksandOtherAttachedStructures).Beforefireseasonbegins,removecombustiblelitteronroofsandguttersandtrimtree•branchesthatoverhangtheroofandchimney(seeFactSheet#9,Gutters).
Zone 2EnsurethatZone2includesonlyindividualandwell-spacedclumpsoftreesandshrubs •and/orafewislandsofvegetationthataresurroundedbyareaswithnoncombustiblematerials.
Figure 2. Combustiblematerialsadjacenttoabuildingcreateahazard(AnchorPointGroup,Boulder,CO).
FS No. 4 – Defensible Space HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of4
Usehardscapefeaturessuchasdrivewaysandpavedorgravelwalkwaysorpatiostocreate•firebreaksthroughouttheyard.Plantfire-resistant,low-volumevegetationthatretainsmoisturewellandneedsminimum•maintenancesuchaspruningandremovingdeadanddyingbranches.Separateauxiliarystructuressuchasadetachedgarage,pumphouse,pergola,andutilityshed•fromthehomebyatleast50feet.Increasethedistanceifthestructureisusedforthestorageofcombustiblematerials.Complywithrecommendedconstructionpracticesrelatedtofireresistanceforauxiliary•structures.SeeFactSheets#5to#16forguidanceonplanninganddesigningastructureinawildfirezone.Ensurethatpatiofurnitureiseithermadeof•noncombustiblematerialsuchasmetalorisatleast30feetawayfromthebuilding.Storepatiofurnitureinalocationthatisprotectedfromignitionbyawildfire.Placewoodpilesatleast30feetfromthe•buildingandstorethewoodinavegetation-freezonesuchasagraveledarea.Storefueltanksawayfromastructureatthe•minimumdistancethatisrequiredbycodeorgreater(seeFactSheet#16,Utilities)andplaceundergroundoronanoncombustiblepad.
Figure 4.AnoncombustiblegroundcoverinZone1helpedthishomesurviveawildfire(AnchorPointGroup,Boulder,CO).
Figure 3. Thethreeconcentriczonesofdefensiblespace.
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Zone 3Reducefuelsthatarefartherthan100feetfromthebuildingbythinningandpruningvegetationhorizontallyandverticallyasdiscussedabove.ThinningandpruninginZone3canbemorelimitedthaninZone2.ThegoalsinZone3aretoimprovethehealthofthewildlandsandhelpslowanapproachingwildfire.Zone3isalsoanaesthetictransitionbetweenthemoreheavilymodifiedZone2andtheunmodifiedsurroundings.
ConsiderationsConsultthelocalorstatefireagencyorqualifiedfiremanagementspecialistaboutcodes,•requirements,andstandardsrelatedtodefensiblespace.Codes,requirements,andstandardsnormallyrepresenttheminimumthatshouldbedone.Considerationshouldbegiventoprovidingenhancedprotectionmeasuresbeyondtheminimumrecommendedorrequired.Maintainingadefensiblespacerequiresroutinemaintenanceofvegetation,whichincludes•pruningandremovingdeadbranchesandleaves.Characteristicsoflow-maintenanceplantsare:
Drought-resistant –
Pest-resistant –
Nativetothearea –
Noninvasive –
Slow-growing –
Wind-resistant –
Sustainablewithoutsupplementalfertilization –
Vegetationmodificationmustbeperformedincompliancewithlocal,state,andfederal•environmentalregulations.
EffectivenessAllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZones.
ResourcesBarkley,Y.C.,C.Schnepf,andJ.Cohen.2005.Protecting and Landscaping Homes in the
Wildland/Urban Interface.StationBulletin#67.Moscow,Idaho:IdahoForest,WildlifeandRangeExperimentStation.www.treesearch.fs.fed.us/pubs/22257.
FirewiseCommunitiesProgram.www.firewise.org/newsroom/faq.htm.
NationalFireProtectionAssociation(NFPA)1144:StandardforReducingStructureIgnitionHazardsfromWildlandFire.2008.http://dnrc.mt.gov/forestry/Fire/Prevention/documents/WUIrewrite/NFPA1144.pdf.
NationalWildfireCoordinatingGroup.www.nwcg.gov.
FS No. 5 – Roofs HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of5
Roofs Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 5
PurposeToprovidegeneralguidanceonthedesignandconstructionofroofassembliesonbuildingsinwildfirezones. Guidancepertainstobothnewandexistingbuildings.
Key Issues Roofassembliesarethemostvulnerable•componentofthebuildingenvelopeinawildfirebecauseoftheirhorizontalorientationandsize.Embersandfirebrandscanignitetheroof•covering,otherroofcomponents,anddebrisontheroof.Oncetheroofhasignited,thefirecommonlypropagatesintotheinteriorofthebuilding,resultinginsubstantialdamagetoortotallossofthebuilding.Theprobabilitythatahomewillsurviveawildfireisgreatlyinfluencedbythecomponentsofthe•roofassembly.Thetypeandarrangementofthecomponentsgoverntheirpotentialforignitionandtheirpropensitytotransferheatintotheinteriorofthebuilding.Thecomplexityoftheroof’sshapealsoinfluencesthepotentialforignition.Aroofwithvalleys•androof/wallintersectionswherecombustibledebrissuchasleavesandneedlescancollecthasmorepotentialforignitionthanaroofwithoutthem.
Fire-rated Roof AssembliesTheresistanceofroofassembliestoexternalfireisratedbytheAmericanSocietyofTestingandMaterials(ASTM),usingtestmethodE108.Themethodincludesmeasurementsofthesurfacespreadofflame,theabilityoftheroofassemblytoresistfirepenetrationfromtheexteriorofthebuildingtotheundersideoftheroofdeck,andthepotentialfortheroofcoveringtodevelopflyingbrandsofburningmaterial.RoofassembliesareratedClassA(highestrating),B,orC.Assembliesthatfailthetest(donotmeettheClassA,B,orCcriteria)areunrated.
ClassAprovidesthegreatestdegreeoffireresistance,butthereisarangeofprotectionwithintheClassArating.Forexample,someClassAratedassemblieshavenoncombustibleroof
Roof covering: Theexteriorroofcoverorskinoftheroofassembly(e.g.,shingles,tiles,slate,metalpanels,roofmembrane).
Roof assembly:Anassemblyofinteractingroofcomponents,includingtheroofdeck,vaporretarder(ifpresent),insulation(ifpresent),insulationcoverboards(ifpresent),andtheroofcovering.
ASTME108testconditionsdonotreplicateactualwildfireconditions.Inmanycases,actualwildfireexposuresaremuchmoreseverethanthoseinducedduringthetesting.
Page2of5 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 5 – Roofs
coverings(suchasclayorconcretetilesandmetalpanels),whileothershavecombustiblecoverings(suchasasphaltshinglesandlow-slopemembranes).
Guidance for New BuildingsManytypesofroofassembliesareratedClassA.RecommendationsforvariouscomponentsofroofassembliesthatareratedClassAareprovidedbelow.
Steep-slope Roof: CoveringAsteep-sloperoofisaroofwithaslopegreaterthan3:12.Thefollowingdesignandinstallationpracticesarerecommended:
Tile. • Clayandconcretetilearenoncombustibleandbecauseoftheirrelativelylargethermalmass,retardthetransferofheat.Lightweighttileproductsareavailable,butnormal-weighttilesarerecommendedbecauseoftheirgreatermass.Iftilesareinstalledoverwoodbattens,embersmaybeblownunderthetilesandignitethebattens.Fire-retardant-treatedbattensarethereforerecommended.Iftileisused,thefollowingarealsorecommended:
Eaves, hips, and ridges. – Emberscanbeblownundertilesattheeaves,hips,andridges.Birdscanbuildnestsinthespacebetweentheunderlaymentandthebottomofthetilesifthespaceisaccessible,providingcombustibledebristhatcanbeignitedbyembers.Installingbirdstopsateavesandfullymortaringhipsandridgesarebothrecommendedtoavoidtheaccumulationofdebrisundertilesandtokeepembersout(seeFigure1).Valleys. – Unlessspecialmetalflashingisinstalled,combustibledebriscanaccumulateinvalleysandthenunderthetiles.Flatandplaintilesshouldbespecifiedtobetightlybuttedtoformaclosedvalley,andpiecesofmetalflashingshouldbeinstalledundereachtilecoursealongthevalleycenterline.Forprofiledtile,leadorflexibleflashingshouldbeused,asrecommendedbythetilemanufacturer(seeFigure2).
Metal shingles and panels.• Metalshinglesandpanelsarenoncombustible,buttheyreadilytransferheat.Iftheyareinstalledoverwoodbattens,fire-retardant-treatedbattensshouldbespecifiedandinstalled.Ifshinglesorpanelsareinstalledoverwooddecking,5/8-inchgypsum
Figure 1.Abirdstopattheeave.
Birdstops prevent debris from accumulating under tiles
OnlyClassAratedroofassembliesarerecommendedforhomesinwildfirezones.
FS No. 5 – Roofs HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of5
roofboardcomplyingwithASTMC11771 shouldbeinstalledoverthedecking.Fiberglass-reinforced asphalt shingles.• Althougharoofassemblythathasfiberglass-reinforcedasphaltshinglescanberatedasClassA,theseshinglescontaincombustiblematerial(e.g.,asphalt).Ifthistypeofshingleisused,a5/8-inchgypsumroofboardthatcomplieswithASTMC1177overthewooddeckingshouldbeinstalledforenhancedprotectionofthedecking.Careneedstobetakenwhentheshinglesarenailedthatthenailsarenotoverdriven.Wood shingles and shakes• . RoofassembliesthathavewoodshinglesandshakescanberatedClassAiftheshinglesorshakesarefire-retardant-treatedandaspecificcapsheetunderlaymentisinstalled.Withouttheunderlayment,themaximumratingisClassB.Notethatwhenshinglesorshakesarefire-retardant-treated,theycannotbeimpregnatedwithpreservativetreatment.Iffire-retardant-treatedshinglesorshakesareinstalledoverwooddecking,installinga5/8-inchgypsumroofboardthatcomplieswithASTMC1177overthedeckingisrecommendedinadditiontothespecialunderlaymentthatisrequiredtoachievea ClassArating.
Steep-slope Roof: Underlayment Emberscanbeblownundersometypesofsteep-slopecoveringssuchastile,slate,andmetalshinglesandpanels.Iftilesbecomedislodgedorcracked,emberscanlandontheunderlaymentbelow(seeFigure3).Installinganunderlaymentthathasenhancedfireresistanceisrecommendedtoprovideprotectionfromembersthatreachtheunderlayment.
Anexampleofanenhancedunderlaymentisamineral-surfacecapsheetthatisratedforuseinaClassAratedassembly.2Ifamineral-surfacecapsheetisusedundermetalpanelsorshingles,measuresshouldbetakentopreventthemetalfrombearingdirectlyonthecapsheetandthecapsheetfromabradingthemetal(therebymakingthemetalsusceptibletocorrosion).
1Boardsthatare5/8-inchthickaretypeX(“specialfire-resistant“).Boardsthatare1/2-inchand1/4-inchthickarenottypeX.
2Althoughcapsheetsarenormallythefinishedsurfaceofabuilt-upormodifiedbituminousroofcovering,acapsheetcanalsobeusedasanunderlayment.
Figure 3. Displacedtilesallowemberentry.
Figure 2.Specialvalleyflashingtoavoiddebrisaccumulationbetweenandbelowtiles(photographcourtesyofMonierLifetile).
Page4of5 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 5 – Roofs
Steep-slope Roof: Decking Mosthomeshaveroofdecksthatareconstructedofwood,typicallyplywoodororientedstrandboard.Fire-retardant-treateddeckingcanbespecifiedtoavoidignitionofthedeck.Formoreprotection,5/8-inchgypsumroofboardscanbespecifiedinadditiontothefire-retardant- treateddeck.
Althoughnotcommoninhomes,noncombustibledeckssuchassteelorconcrete,includingconcretetoppingoversteeldecking,canbespecified.Inadditiontobeingnoncombustible,concretedecksoffergreatresistancetoheattransferandfirepenetrationthroughthedeckfromtheexterior.
Low-slope Roof: Covering and UnderlaymentLow-sloperoofshaveslopeslessthan3:12.Avarietyoflow-sloperoofcoveringsandassembliesareavailablewithaClassArating.
Ifalow-slopeassemblyisselected,thefollowingrecommendationsshouldbefollowed:Polyisocyanurateroofinsulationshould•bespecified(seeFigure4).A5/8-inchgypsumroofboardthat•complieswithASTMC1177immediatelybelowtheroofmembrane(seeFigure4)shouldbespecified.Forenhancedfireresistance,inadditiontotheaboverecommendations,theroofmembrane•shouldbeprotectedwithheavyweight(i.e.,17poundspersquarefootminimum)concretepavers(seeFigure5).
Ifpaversareplacedoverabuilt-upormodifiedbitumenmembrane,alayerofextruded –polystyreneinsulation(intendedforprotectedmembranesystems)overthemembraneshouldbespecified.
Figure 5.Concretepaversovermembrane(FEMA55).
Mortar-faced extruded polystyrene
Roofparapet
Extruded polystyrene
Concrete pavers
Membrane
Polyisocyanurate insulation
Roof membrane
5/8-inch gypsum board
Roof deck
Figure 4. Componentsofalow-slopedroof.
FS No. 5 – Roofs HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page5of5
Additionally,forsmooth-surfacedbuilt-upandmodifiedbitumenmembranes,asheet –ofpolyethylene(minimumof4mils)shouldbespecifiedbetweenthemembraneandpolystyrenetokeepthepolystyrenefrombondingtothemembrane.Toprotectthebaseflashings,amortar-facedextrudedpolystyreneboardshouldbeinstalled –overthebaseflashing(seeFigure5).
Low-slope Roof: Decking Roofdeckingdesignandconstructionarethesameforsteep-slopeandlow-sloperoofs.Seethediscussionundersteep-sloperoofsabove.
Guidance for Existing BuildingsForhomeownerswithroofassembliesthatarenotClassArated,theonlylong-term,reliablewaytoreduceroofvulnerabilitytowildfireistoreroof.Reroofingnormallyinvolvesremovingthematerialsabovetheroofdeckandreplacingthemwithnewmaterials.Therecommendationsthatarelistedabovefornewbuildingsareapplicabletoreroofingdesignandinstallation.
RoofassembliesthathavewoodshinglesorshakesandarenotratedClassAandroofswithorganic-reinforcedasphaltshinglesarevulnerabletoawildfire.Thesetypesofroofsshouldbereplacedassoonaspossible.
ConsiderationsThehomeownershouldhaveroofdebrisremovedfromtheroofsurfaceandguttersregularly.•Agingdoesnotaffecttheignitionpotentialoftile.However,someroofcoverings,suchaswood•orfiberglass-reinforcedasphaltshingles,becomemoresusceptibletoignitionastheyage.Theroofcoveringshouldbereplacedbeforedeteriorationofthecoveringsignificantlydegradesresistancetoignition.Birdstopsshouldbeinspectedannuallytoensurethattheyhavenotfallenoutofplace.•Forrecommendationsonvents,seeFactSheet#8,Vents.•Forrecommendationsonguttersanddownspouts,seeFactSheet#9,Guttersand•Downspouts.
EffectivenessAllmitigationmeasuresrecommendedinthisFactSheetareeffectiveinallFireSeverityZones.
ResourcesAmericanSocietyofTestingMaterials(ASTM).2007.Standard Test Methods for Fire Tests of Roof
Coverings.ASTME108-07a.
FEMA.2003.Coastal Construction Manual.FEMA55.
FS No. 6 – Eaves, Overhangs, and Soffits HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of3
Eaves, Overhangs,and Soffits Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 6
Purpose Toprovideguidanceonthedesignandconstructionofeaves,overhangs,andsoffitsinwildfirezones.Theguidancepertainstobothnewandexistingbuildings.
Key IssuesWindborneembers,convectiveheat,andradiantheatcanbetrappedunderoverhangsand•intheupperportionofexteriorwalls.Overhangsandwallscanigniteifnotconstructedofnoncombustibleorfire-resistantmaterials.Typicalconstructionmaterialsforeaves,overhangs,andsoffitsarenotfire-resistantandare•thereforesusceptibletoignitionbyembersandhotgases.Onceaneave,overhang,orsoffithasignited,firecanspreadontotheroof,intotheattic,or•ontoandthroughtheexteriorwall.Soffitsnormallyhaveventsaspartoftheatticventilationsystem.Unprotectedventscanallow•embersandhotgasestoentertheattic(seeFactSheet#8,Vents).
Typical Design and ConstructionEaves. Eavesarelocatedatthedown-slopeedgeofaslopedroofandserveasthetransitionbetweentheroofandfascia/wall.Aneavetypicallyhasametaledgeflashingandgutterthatareattachedtoawoodfasciatrimboard.
Overhangs. Overhangsareextensionsoftheroofbeyondtheexteriorwall(i.e.,thejoists,rafters,ortrussesandthedeckingtheysupportcantileverpastthewall).Anoverhangprotectstheupperportionofthewallthatitisattachedtofromrainfall,anditalsoshadesthewindowsunderitfromthesun.Overhangscanbeopen,inwhichthetrusses/raftersanddeckingareexposed(seeFigure1),orenclosedbyasoffit.
Soffits.Asoffitenclosestheundersideofsloped-orflat-roofoverhangs.Soffitsarecommonlyconstructedfromfiber-cementpanels,metalpanels,stucco,vinylpanels,orwoodsheathing.Metalpanels,untreatedwoodpanels,andvinyl
Attic vents
Figure 1. Anopenoverhang.Theexposedtimberraftersanddeckingaresusceptibletoignition,andembersandhotgasescanentertheatticthroughunprotectedvents.
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panelsarevulnerabletodamagefromwildfires.Metalpanelsconductheatandcandistortandallowpassageofembersandhotgases.Untreatedwoodpanelscanignite,andvinylpanelscanmeltandfallaway.
Guidance for New BuildingsConsiderdesigningthebuildingwithout•overhangs(seeFigure2)toavoidthefire-relatedproblemsassociatedwithsoffitsorminimizeasmuchaspossibletheextentoftheoverhangtoreducethepotentialforentrapmentofembersandhotgases.Ifnooverhangsorshortoverhangsare•unacceptablebecauseofaestheticsoradesiretoprotectthewallsfromrainfallorwindowsfromthesun,implementthefollowingrecommendedmeasures:
Encloseoverhangswithsoffitsthathave –aminimum1-hourfire-resistanceratingtopreventembersandhotgasesfrommakingcontactwiththejoists,raftersortrusses,ortheundersideoftheroofdecking.Useflat,horizontalsoffits(seeFigure3)insteadofattachingthesoffitstotheslopedjoists, –whichcreatesslopedsoffits.Aflatsoffitreducesthepotentialforentrapmentofembersandhotgases.
Forthefascia,usenoncombustibleorfire-resistantmaterials(e.g.,fire-retardant-treated•lumber,fiber-cementboard).Foreavevents,followtheguidanceinFactSheet#8,Vents.•
Embers and hot gases from fire
Exterior wall cladding
Fascia
Gutter
Rafter
Underside of roof deck
Figure 3. An enclosed overhangwithahorizontalsoffit.
Figure 2.Aneavewithessentiallynooverhang.
Gutter
Embers and hotgases from fire
Horizontalsoffit
Exterior wall cladding
Fascia
RafterUnderside of roof deck
Soffit framing
FS No. 6 – Eaves, Overhangs, and Soffits HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of3
Guidance for Existing BuildingsInstallasoffitunderopenoverhangsaccordingtotheguidanceprovidedabove.•Evaluatethefire-resistanceofexistingsoffitsandreplacesoffitsthatarenotfire-resistant•accordingtotheguidanceprovidedabove.Someexistingsoffits(suchasthoseconstructedofplywood)canbecoveredwithanoncombustibleorfire-resistantmaterialsuchasfiber-cementboardorstucco.InveryhighFireSeverityZones,installexterior5/8-inchfire-resistantgypsumboardbetween•theexistingandnewsoffitmaterialsforenhancedfireresistance.Ifthefasciaiscombustible,coverthefasciaboardwithanoncombustibleorfire-resistant•material(e.g.,fire-retardant-treatedlumber,fiber-cementboard).Foreavevents,followtheguidanceinFactSheet#8,Vents.•
ConsiderationsPlantingcombustiblevegetationundereavesandoverhangsshouldbeavoided(seeFactSheet#4,DefensibleSpace).
EffectivenessAllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZones.
ResourcesUnderEaveSFMStandard12-7A-3,2001CaliforniaReferencedStandardCodes(Part12,
Title24,C.C.R.).http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdf.
FS No. 7 – Exterior Walls HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of3
Exterior Walls Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 7
PurposeToprovideguidanceonthedesignandconstructionofexteriorwallsinwildfirezones.Guidancepertainstobothnewandexistingbuildings.
Key Issues • Exteriorwallsaresusceptibletowildfireflames,conductiveheat,andradiantheat.Flamesandheatcanignitecombustiblewallcoverings.Whenexteriorwallsignite,thefirecanspreadtoothercomponentsofthebuildingsuchastheroof,soffit,windows,anddoors,resultinginsubstantialdamagetoortotallossofthebuilding.
• Windborneembersandfirebrandsarealsosourcesofignition.Emberscanbecometrappedincracksinwalls,windowopenings,anddoortrimboardsandignitecombustiblematerials.Windbornefirebrandscanignitewallcoverings.
• Thefireresistanceofexteriorwallsdependsprimarilyonwhatthewallsareconstructedofandtheamountofnearbycombustiblematerial.Sometypesofconstructionmaterialssuchasvinylsidingdonotburnbutcanmeltwhenexposedtohightemperatures(seeFigure1),allowingthefiretoreachtheunderlyingwallcomponentsandpenetratetheinteriorofthebuilding.
Guidance for New Buildings• Forthebestprotection,ensurethatexteriorwallcoveringsarenoncombustibleorfire-resistantandnotsusceptibletomelting.Concrete,fiber-cementpanelsorsiding,exteriorfire-retardant-treatedwoodsidingorpanels,stucco,masonry,andmetalarerecommendedmaterials.Withthesecoverings,thecoveringitselfshouldnotigniteandfuelthefire.Examplesofthetypesofcoveringsthatarenotrecommendedarewoodsidingthatisnotfire-retardant-treated,vinylsiding,metalsidingsusceptibletowarping,andanexteriorinsulationfinishsystem.
• Ensurethattheentirewallassemblyhasafire-resistanceratingtestedinaccordancewithAmericanSocietyforTestingandMaterials(ASTM)E119.Althoughtheaboverecommendedtypesofcoveringsprovideaninitialbarriertoflames,heatmaypassthroughthecovering
Figure 1.Vinylsidingthatmeltedandwarpedduringawildfire(firecenter.berkeley.edu).
Page2of3 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 7 – Exterior Walls
andigniteunderlyingwallcomponents.Afire-resistanceratingindicateshowlongundertestconditionsawallassemblycanpreventflamesandheatfrompassingthroughthewall.Aminimumfire-resistanceratingof1hourisrecommended,buthigherratingsprovidegreaterprotection.
• Complywiththerequirementsofthefire-ratedassembly,includingusingtheexacttypeofmaterials,configuration,andattachmentusedduringthetestingthatestablishedtherating.
• Forexceptionalfireresistance,useinsulatedconcreteform(ICF)walls,cast-in-placeconcrete,orfullygroutedconcretemasonryunits.IfICFisselected,useastuccoormasonrywallcoveringtoprotecttheplasticfoamforms.
• Iffiber-cementormetalwallcoveringsareused,installonelayerof5/8-inchtypeXexteriorgypsumboardwithtapedjointsunderneathhousewrap(seeFigure2).Forfiber-cementsiding,thegypsumboardprovidessecondaryprotectionifthesidingdecomposesandfallsawayduringafire.Formetalpanels,thegypsumboardminimizesthetransferofheatradiatedfromthemetalpanelstootherwallcomponents.
• Forvinylsiding(notethatvinylsidingisnotrecommended),installonelayerof5/8-inchtypeXexteriorgypsumboardwithtapedjointsunderneathhousewrap.Ifthevinylandhousewrapmeltduringafire,theunderlyinggypsumboardwillprovidesomeprotection.
• Usenoncombustibleorfire-resistantmaterialsuchasexteriorfire-retardant-treatedwoodorfiber-cementfortrimboardsarounddoors,windows,eaves,andcorners.
Guidance for Existing Buildings• Replaceexteriorwallcoveringsthatarecombustible,aresusceptibletomelting,orcanreadilytransmitheatwithoneoftherecommendedcoveringslistedabove.Examplesofthetypesofcoveringsthatneedtobereplacedarewoodsidingthatisnotfire-retardant-treated,vinylsiding,metalsiding,andanexteriorinsulationfinishsystem.
Beforereplacingvinylormetalsiding,checkwhetherthereisanunderlyinggypsumboard –substrate.Ifso,remedialworkmaynotbeneeded.
Determinewhetherkeepingtheexistingcoveringandcoveringitwith5/8-inchtypeX –gypsumboardandanewcoveringisaviableoption.
Considerations• Forstudwalls,metalstudscanbeusedinlieuofwoodstuds.Metalstudsdonotignite,buttheytransferheatmorereadilythanwoodstudsandcandeformandcollapseattemperaturesthatcanoccurinawildfire.Currentdataareinsufficientregardingthewildfireperformanceof
Figure 2.Exampleofafire-ratedwallassembly.
Exterior covering
Wall stud
Sill plate
5/8-inch type X exterior gypsum board
Wood sheathing
Housewrap
FS No. 7 – Exterior Walls HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of3
wallsthathavewoodstudsversusmetalstuds.• Maintainingandremovingcombustibledebris(suchasvegetationandleaves)andfirewoodneartheexteriorwallsregularlyreduceabuilding’svulnerabilitytoignitionduringawildfire(seeFactSheet#4,DefensibleSpace).
EffectivenessAwallassemblywithoneoftherecommendedcoveringsandaminimum1-hourfire-resistanceratingiseffectiveinallFireSeverityZones.
ResourcesASTME119-08aStandardTestMethodsforFireTestsofBuildingConstructionandMaterials.
http://www.astm.org/Standards/E119.htm.
MaterialsandConstructionMethodsforExteriorWildfireExposure:ExteriorWallSidingandSheathingSFMStandard12-7A-1,2001CaliforniaReferencedStandardCodes(Part12,Title24,C.C.R.).http://www.fire.ca.gov/fire_prevention/downloads/%20Part_12_CA_SFM_12-7A-1_Test_Standards.pdf.
FS No. 8 – Vents HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of5
Vents Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 8
Purpose Toprovideinformationaboutwaystoavoidwindborneembers,convectiveheat,andradiantheatenteringexteriorventopenings,whichcanleadtotheignitionofinteriorbuildingcomponentsandcontents.Guidancepertainstobothnewandexistingbuildings.
Vent Systems and Vent OpeningsVentscanbedividedintothoseforattics;ventilatedcathedralceilings;crawlspaces;andheating,ventilation,andairconditioning(HVAC)systems.
Attic and Cathedral Ceiling Vents Ridge vent• —acontinuousventinstalledalongthefulllengthoftheroofridge.Ridgeventsallowexfiltrationofatticair,orinventilatedcathedralceilingsorventilatednailbaseboards,theexfiltrationofairfromtheventilationcavityofthecathedralceilingornailbaseboards.Ridgeventsaremetalorplastic.Someridgeventshaveinternalbafflemediatoavoidtheentranceofwind-drivenrainandsnow.Soffit vent• —acontinuousorintermittentventinstalledalongasoffit.Soffitventsprovideairintakeintotheatticorintotheventilationcavityofcathedralceilingsandventilatednailbaseboards.Soffitventsaremetalorplasticandoftenhaveascreentopreventinsectentry.Vinylandmetalsoffitsarecommonlyventedbyintermittentlyspaced,perforatedsoffitpanels.Gable-end vent• —aventlocatedinthegable-endwall,justbelowtheroofridge.Gable-endventsallowairtoflowintoandoutofattics.Gable-endventsnormallyhavelouverbladestoavoidtheentranceofwind-drivenrainandsnow(seeFigure1).Thistypeofventiscommonlymetalandnormallyhasaninsectscreen.Through-roof vent• —aventthatpenetratestherooftoallowexfiltrationofatticair;alsoknownasaneyebrowordormervent.Through-roofvents,includingsheetmetal“goose-necks,”arealsoavailableforkitchenorbathroomexhaustducts.Through-roofventsaremetal,plastic,orrigidfiberglass.
Figure 1. Alouveredventopeningcanbeusedforgable-endventingorforconnectiontoductwork.
Horizontal louvers can prevent embers from entering the ventilation system
Page2of5 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 8 – Vents
Crawlspace VentsCrawlspace vent• —aventinstalledintermittentlythroughthefoundationwallseveralinchesabove-grade.Crawlspaceventsallowairtoflowintoandoutofthecrawlspace.
HVAC System VentsThrough-roof vent• (seeabove).Wall louvers• —aventopeningonanexteriorwall(seeFigure1).WalllouversareconnectedtotheHVACductworkwhereairentersorisexhaustedfromthebuilding.Louversarecommonlymetal.Thelouverbladesarenormallyinafixedposition(i.e.,cannotberotated),butsomehavemoveablebladesthatcanberotatedtoclosetheventopening.
Key IssuesEmbersandhotgasescanbeblownorpulled•intoventopeningsandenteratticspaces,crawlspaces,andductwork,leadingtoignitionoftheinteriorofthebuilding(seeFigure2).Debriscanaccumulateatventopeningsand •igniteduringawildfire.
Guidance for New Buildings
All Vents Specifyandinstallnoncombustiblematerialforallvents.Metalproductsarerecommendedfor•ventsandventflashing.Specifyandinstallcorrosive-resistant,metalmeshscreenswithamaximumopeningof•1/4inchatallventopenings.Specifyandinstallventopeningswithamaximumnetfreeareaof144squareinches.•Placeallventopeningsatleast10feetfromotherbuildingsorpropertylinestoavoidignition•fromembersandhotgasesfromanadjacentbuildingthathasignited.
Attics (including Cathedral Ceiling and Ventilated Nailbase Boards) Protectingatticspacesfromwildfiresisachallengebecauseairisnaturallydrawnintoatticsthroughventopenings.Althoughinsectscreenscanpreventtheentryofmanyembers,ventscreensandlouversdonotpreventtheentryofhotgases.Ventsthatallowairtoflowintoandoutundernormalconditionsandalsoavoidtheentryofembersandhotgasesinawildfirecanbeprovidedinthefollowingways:
Gable-end vent• .Insteadofusingridgevents,specifyandinstallgable-endventswithspeciallydesignedmetalshutters.Whenawildfirethreatens,theshutterscanbeplacedoverthegable-endvent.Ahingedshutterthatcanbelatchedinanopenorclosedpositionisrecommended(seeFigure3).Adetachableshutterdesigncanbeused,butwhentheshuttersareneeded,
Figure 2. Embersorhotgasescanbeblownorpulledintovents.
FS No. 8 – Vents HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of5
thehomeownermustrememberquicklywheretheyarestored.Shuttersshouldhaveagasketthatprovidesatightsealbetweentheshutterandgable-endvent.Foramoreconservativeshutter,ashutterwithaninsulatedcoreencapsulatedbymetal(similartoarefrigeratordoor)canbeused.Whengable-endventsarecombinedwithsoffitvents,effectiveatticventilationcanbeachievedwhentheatticspaceissimpleandrelativelysmall,suchasasmall,gable-roofedhouse.Ifthehousehasacomplexroofareaortheatticistoolargetobeeffectivelyventilatedbygable-endvents,ridgeventsorthrough-roofventsshouldbeused.Ridge vent• .Continuousridgeventscanprovideeffectiveventilation,buttypicalridgeventsarenothighlyfire-resistant.Althoughairisnormallyexhaustedthroughridgevents,hotgasescanentertheridgeventandflowintotheattic.Emberscanalsoenterthroughtheridgeventiftheventdoesnothaveinternalbafflemedia.Typicalridgeventsarethereforenotrecommendedunlesstheatticconfigurationorsizerequiresridgeventstoventilatetheatticeffectively.Ifridgeventsareused,metalventswithinternalbafflemediaarerecommended,butduringawildfire,theinternalbafflematerialmaymeltandbecomeineffective in atpreventingembersfromentering.Soffit vent• . Aswithridgevents,typicalsoffitventsarenothighlyfire-resistant,butbecausetheyareanecessaryelementofaventedattic,theycannotbeeliminated.Toavoidembersandhotgasesfromenteringthevents,speciallydesignedmetalshuttersoverthesoffitventopeningsshouldbespecifiedandinstalled.Seetheshutterrecommendationsforgable-endventsabove.Through-roof vent• . Through-roofventsarenotrecommendedforatticventilationbecausethereisnoknowneffectivestrategyforavoidingembersandhotgasesfromentering,otherthanblockingthevent.A1/4--inchscreeniseffectiveatkeepingoutfirebrandsandembersthatarelargerthan1/4-inchbutwillnotkeepoutsmallerembersorhotair.
Shutter with fire-resistant gasket
Shutter latched in open position
Wall louver vent
Shutter manually latched in closed position at the onset of a wildfire
The Unventilated AtticThemostconservativeapproachtopreventingembersandhotgasesfromenteringtheatticistoeliminateatticventilation,butunventilatedatticsarecontroversial.AlthoughallowedbytheInternationalResidentialCode,providedtheCode’scriteriaaremet,unventilatedatticsmaynotcomplywithlocalbuildingcodes.
However,whenunventilatedatticsareallowedbythebuildingcodeorcodecomplianceisnotanissue,andwhenclimaticandinteriorhumidityconditions(e.g.,noindoorswimmingpools)areconducivetoanunventilateddesign,anunventilatedatticisareliablewaytopreventembersandhotgasesfromenteringtheattic.
Figure 3.Ahingedshutter.
Page4of5 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 8 – Vents
Becauseofvariablereliabilityofblockingtechniquesandthepotentialdangerofhomeownersfallingfromroofswhileattemptingtoblockvents,blockingisnotrecommended.
Crawlspace Vents Specifyandinstallspeciallydesignedmetalshuttersovercrawlspaceventopenings.A1/4-inchmeshscreenshouldalsobeinstalledovertheventopening.Seetheshutterrecommendationsforgable-endventsabove.
HVAC System VentsWall louvers• . Specifyandinstallspeciallydesignedmetalshuttersoverwalllouvers(seetheshutterrecommendationsforgable-endventsabove)orspecifyandinstallwalllouversthathaveadjustabletight-fittingbladesthatcanbeclosedwhenawildfirethreatens.Asanadditionalconservativemeasurewitheithershuttersoradjustableblades,specifyandinstallfiredamperswithintheductsimmediatelybehindthewalllouvers.Ifsufficientlyhighheatpenetratesbeyondthelouver,thefiredamperwillautomaticallycloseandpreventhighheatfrompenetratingfarther.Through-roof vents• .Asdiscussedinatticventilation,through-roofventsarenotrecommended.Ratherthanrunningductworkthroughtheroof,extendtheductworktoanexteriorwallwhereitcanbefittedwithawalllouverandshutter.Ifitisnecessarytopenetratetheroof,however,installafiredamperintheductattheplaneoftheroofassembly.
Guidance for Existing Buildings Ifthehomehasridgeventsorwalllouversandtheyarenotmetal,replacethemwithmetal•ventsaccordingtotheguidanceprovidedabove.Ifexistingventopeningsdonothavescreensorifthescreenopeningsarelargerthan•1/4-inch,installmetalscreensaccordingtotheguidanceprovidedabove.Installshuttersovergable-endvents,soffitvents,crawlspacevents,andwalllouvers.Ifthe•existingwallorsoffitiscombustible,shuttersmaynotbeeffective.Inthiscase,installingshuttersisprobablycost-effectiveonlyifdoneinconjunctionwithupgradestothewallorsoffit.
ConsiderationsLow-profile,through-roofventshavebeenusedinplaceofsoffit/eaveventswithgreatsuccess,•butnoneoftheseproductshavebeentestedatthetimeofthispublication.Thehomeownershouldperiodicallyhaveaprofessionalremovedebristhathasaccumulated•nearoronventopenings,ventscreens,andlouverblades.Theamountofvegetationnearventopeningsshouldbelimited(seeFactSheet#4,Defensible•Space).Tominimizethepossibilitythatembersandhotgaswillbepulledintothehome,theHVAC•system,includingexhaustfans,shouldbeturnedoffwhenawildfirethreatens.Atticexhaust
FS No. 8 – Vents HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page5of5
fansshouldalsobeshutdown.Atticexhaustfansthatarecontrolledbyathermostatmayneedtobedeactivatedbytrippingthecircuitbreaker.Forsoffitconstruction,seeFactSheet#6,Eaves,Overhangs,andSoffits.•
EffectivenessAllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZonesexceptasnotedbelow.Ifaridgeventisinstalled,theventopeningmaybebreachedduringextremefireexposureby•embersorhotgases,whichcouldresultinignitionoftheattic.Theeffectivenessofshutter-protectedventopeningsisdependentonthedeploymentofthe•shuttersbythehomeownerpriortofireexposure.
ResourcesSlack,P.2000.Firewise Construction Design and Materials.ColoradoStateForestService.
UnderEaveSFMStandard12-7A-3,2001CaliforniaReferencedStandardCodes(Part12,Title24,C.C.R.).Availableatwww.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdf.
FS No. 9 – Gutters and Downspouts HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of2
Gutters and Downspouts Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 9
PurposeToprovideguidanceaboutinstallingfire-resistantguttersanddownspoutstoreducethepotentialfordamagetohomesandotherbuildingsfromwildfires.Guidancepertainstobothnewandexistingbuildings.
Key IssuesDebrissuchasbranches,leaves,andpineneedlescan•becometrappedingutters(seeFigure1).Thedebriscanbeignitedbyflyingembersorfirebrandsduringawildfire,andthefirecanspreadtotheroof.
Guttersanddownspoutsareoftenconstructedof•plastic.Plasticcanmeltwhenexposedtothehightemperaturesthatcanoccurduringawildfire.
GuidanceInstallnoncombustibleleafguardsoverguttersto•preventtheaccumulationofcombustibledebris.Typesofleafguardsincludemetal-meshscreensandmetalhoodsthatfitintothegutter(seeFigure2).
Useguttersanddownspoutsconstructedof•noncombustiblematerialssuchasgalvanizedsteel,copper,andaluminum.Metalhoodleafguardsarerecommendedbecausetheydonotmeltandarerelativelyeffectiveinkeepingdebrisoutofgutters(seeFigure2).
ConsiderationsIntenseheatfromawildfirecandistortnoncombustible•gutters,leafguards,anddownspouts,andtheymayneedtobereplacedafterawildfire.
Someleafguardscanbecomedislodgedovertime,reducingtheireffectiveness.•
Figure 2.Leafguardsallowrainwaterintothegutterbutkeepcombustibledebrisout.
Leaf guard
Figure 1. Debrisingutterscanigniteandleadtoignitionoftherooforfasciaboard.
Page2of2 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 9 – Gutters and Downspouts
Sometypesofleafguardsdonotpreventalltypesofdebrisfromaccumulatinginthegutter.•Forexample,mesh-typeleafguardsallowpineneedlestoaccumulate.Leafguardsandguttersshouldthereforebecheckedregularlyanddebrisremovedifnecessary.
EffectivenessNoncombustiblegutters,leafguards,anddownspoutsareeffectiveinallFireSeverityZones.
FS No. 10 – Windows and Skylights HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of4
Windows and Skylights Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 10
PurposeToprovideinformationaboutmeasuresthatcanbetakentoavoidtheignitionofinteriorbuildingcomponentsandcontentsduetotheintrusionofwindborneembers,hotgases,andradiantheatthroughwindows,slidingglassdoors,doorvisionpanels,andskylights.Guidancepertainstobothnewandexistingbuildings.
Key IssuesGlazinginhomesistypicallyvulnerabletowildfire•(seeFigure1).(“Glazing”referstotheglass,plastic,orfiberglass-reinforcedtranslucentmaterialinwindows,slidingglassdoors,doorvisionpanels,andskylights.)Failedglazingallowseasypassageofembers,hotgases,andradiantheatintotheinteriorofthebuilding.Glazingisvulnerabletowildfireintwoways:
Flameimpingementandradiantheatcanbe –severeenoughtomeltorbreakmanytypesofglazing.Asinglepaneoftypicalresidentialglasscanfailwithin5minutesofexposuretoawildfire(Slack,2000).Windbornefirebrandscanhavesufficient –momentumtobreakmanytypesofglazing.
Theframesforwindows,slidingglassdoors,and•skylightsareconstructedofmetal,plastic,wood,oracombinationofthesematerials.Plasticandwoodenframesaresusceptibletofailurefromburningormelting(seeFigure2).Iftheframeorsashfails,theentireglazingmayfallout.
Guidance on New BuildingsThissectionprovidesguidanceonglazing,frames,fire-ratedassemblies,andexteriorwindowshutters.
Figure 1.Potentialdamagetoawindowduringawildfire.
Embers melt vinyl frames and ignite wooden frames
Radiant heat and windborne firebrands can shatter windows and lead to interior damage
Figure 2.Combustibleframing(firecenter.berkeley.edu).
Page2of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 10 – Windows and Skylights
Glazing Avarietyofproductsareavailableforglazinginwindows,slidingglassdoors,doorvisionpanels,andskylights.Glazingcanbeinasingle-ormulti-panedconfiguration.Therecommendedglazingproductsforhomesinwildfirezonesarelaminatedglass,temperedglass,glasswithalow-emissivity,fiberglass-reinforcedtranslucentglazing,andinsulatedglazingunits(IGUs).Glazingproductsthatarenotrecommendedareannealedglass,ceramicglass,andplasticglazing.
RecommendedLaminated glass• . Laminatedglassprovidesresistancetowindbornefirebrands.Ifafirebrandstrikeswithenoughmomentumtobreaktheglass,theplasticfilminthecoreoftheglasswillkeeptheglazingintheframe,allowingthebrokenglasstocontinuetoresistfirebrandimpacts,embers,andhotgases.Iftheplasticfilminthecoregetssufficientlyhot,thepanewilldelaminatewhetherornottheglasshasbeenbroken.Iflaminatedglassisspecified,itshouldeitherbeprotectedbyshutters,asdiscussedbelow,orcombinedwithtemperedglassinanIGU.SeetheinformationonIGUsbelow.Tempered glass• .Temperedglassismoreresistanttoheatandflamesthanlaminatedglassorannealedglass(seebelow).Theresistanceoftemperedglasscanbeenhancedwithalow-ecoatingoraproprietaryreflectivecoating,asdiscussedbelow.Firebrandswithsufficientmomentumcanbreaktemperedglass.Toavoidbreakage,theglasscanbeprotectedbyshutters,asdiscussedbelow.AnotheralternativeistospecifyandinstallanIGUwithalaminatedglassinnerpane.Low-emissivity (low-e) coating• . Glasswithalow-ecoatingprovidesahigherlevelofresistancetoradiantheatthanothertypesofglazingbecausethecoatingreflectsradiantheat,reducingtheprobabilitythattheheatwillbeabletoenterthebuilding.Thecoatingshouldbeontheinnersurfaceoftheexteriorpane.Proprietary fiberglass-reinforced translucent glazing• .Thisproductisavailableforskylightsandwalls.TheskylightmaterialhasaClassArating.SeeFactSheet#5,Roofs,foradiscussionofthistypeofrating.Insulated glazing unit. • AnIGUconsistsoftwoorthreepanesofglassthatareseparatedbyasealedairspace.Double-panedannealedunitslastabout10minutesinawildfire,twiceaslongassingle-panedwindows.Inmanycases,10minutesislongenoughtoprovideprotectionfromthefire.Ifthefirstpanefails,thesecondpanemuststillbepenetrated(Slack,2000)(seeFigure3).Laminatedglass,temperedglass,andglasswithalow-ecoatingcanbecombinedinvariouswaysintoanIGU.
Two panes of glass with a layer of air between
The first pane may shatter within 5 minutes of theonset of a wildfire
The second pane offers 5 minutes of additional protection
Figure 3. Double-panedglazing.
FS No. 10 – Windows and Skylights HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of4
NotRecommendedAnnealed glass• .Annealedglass(alsoknownascommonfloatglass)iscommonlyusedinresidentialwindows.Annealedglassisthemostsusceptibletowildfiresofthevariousglasstypesandisnotrecommendedforhomesinwildfirezonesunlessprotectedbyshutters,asdiscussedbelow.Ceramic glass.• Thisspecialtyglassiseffectiveatresistingflames,butittransmitsradiantheatreadily.Ifceramicglassisusedforexteriorglazing,heatthatishighenoughtocauseignitioncanbetransmittedintotheinteriorofthebuilding.Ceramicglassisnotrecommendedforhomesinwildfirezones.Plastic glazing.• Acrylicandpolycarbonateareoftenusedinskylightsandsometimesinwindows.Becauseplasticglazingcanmeltduringawildfire,itisnotrecommendedforhomesinwildfirezones.
FramesAvarietyofproductsareavailableforwindowandskylightframes.Toavoidwindowfailure,framesshouldbeconstructedonlyofmetalormetal-cladwood.Woodenandplasticframesshouldnotbeused.
Fire-rated AssembliesIfafire-ratedwallisspecified,windowsandslidingglassdoorsthatarecommensuratewiththewallintermsofthefireratingarerecommended.Forexample,awindowwitha1½-hourratingisintendedtobeusedinawallwitha2-hourrating,andadoorwitha3/4-hourratingisintendedtobeusedinawallwitha1-hourrating.However,awindowwithahigherfireratingmaybeused.SeeFactSheet#7,ExteriorWalls,forinformationaboutfire-ratedwalls.
Ifafire-ratedwallisnotspecified,anIGUwithametalormetal-cladwoodenframeshouldbeused.SeetheinformationonIGUsabove.
Exterior Window ShuttersExteriorwindowshutterscanprovideprotectionforwindowsandslidingglassdoorsinawildfire.Solidmetalshuttersareunlikelytoigniteormeltandarethereforerecommendedoverwoodenorplasticshutters(seeFigure4).Forenhancedprotection,aninsulatedmetalshuttercanbedesignedandfabricated.Ifthebuildingislocatedinawindbornedebrisregionwithinahurricane-proneregion,theshuttershouldmeetthewindbornedebriscriteriaintheAmericanSocietyofCivilEngineersstandard,ASCE7-05(2006).
Figure 4. Thismetalshutterhastopandbottomtracksthatarepermanentlyanchoredtothewall(FEMA577).
Page4of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 10 – Windows and Skylights
Guidance on Existing BuildingsWindowsandslidingglassdoors,includingframes,thataresusceptibletodamagefrom•awildfireshouldbereplacedwiththecomponentsthatarerecommendedaboveand/orprotectedbyshutters,asrecommendedabove.Doorvisionpanelsthataresusceptibletodamagefromawildfireshouldbereplacedwith•temperedglasswithalow-eorproprietaryreflectivecoating,providedthedoorhassufficientfireresistance(seeFactSheet#11,ExteriorDoors).Skylightswithplasticglazingshouldbereplacedwithoneoftherecommendedtypesof•glazing,asdescribedabove.
ConsiderationsShuttersprotectthehomenotonlyfromwildfiresbutalsofromextremeweather.•Double-panedglassismoreenergyefficientthansingle-panedglass.•Aproprietaryreflectivecoatingisavailableforapplicationtotemperedglass.Thecoatingacts•likealow-ecoatinginthatitreflectsradiantheat,buttheproprietaryreflectivecoatingmaybemoreeffective.Formoreinformationonthisproductandacomparisonoffireratingsofvarioustypesofglassproductsandsizes,seewww.safti.com.
EffectivenessWindowassemblieswith3/4-hourminimumratingsareeffectiveinallFireSeverityZones.•Metalcladdingonmetalclad-woodframesmaybecomedistortedduringwildfireexposureand•requirereplacement.Temporaryshuttersareeffectiveonlyifthehomeownerhassufficienttimetoputtheshutters•intoplace.
ResourcesAmericanSocietyofCivilEngineers.(2006).Minimum Design Loads for Buildings and Other
Structures.ASCE7-05.
CenterforFireResearchandOutreach.UniversityofCalifornia,Berkeley:CollegeofNaturalResources.http://firecenter.berkeley.edu/default.htm.
ExteriorWindowsSFMStandard12-7A-2,2001CaliforniaReferencedStandardCodes(Part12,Title24,C.C.R.).http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-2_Test_Standards.pdf.
FEMA.2007.Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High Winds: Providing Protection to People and Buildings. RiskManagementSeries,FEMA577. http://www.fema.gov/library/viewRecord.do?id=2739.
FireRatedGlazingSolution.www.safti.com.
Slack,P.2000.Firewise Construction Design and Materials. ColoradoStateForestService.
FS No. 11 – Exterior Doors HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of3
Exterior Doors Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 11
Purpose Toprovidebasicguidanceonthedesignandconstructionofexteriordoors,includinggaragedoors,onbuildingsinwildfirezones.Guidancepertainstobothnewandexistingbuildings.
Key IssuesExteriordoorsaresubjecttothesame•typesofexposureasexteriorwallsinawildfire(seeFigure1).However,exteriordoorsaretypicallymuchthinnerandlessfire-resistantthanexteriorwallsandcanthereforeburnthroughmuchfaster.Flamesandhotgasescanignite•combustiblematerialsinadooranddoorframe.Flamesandhotgasescanpenetrate•openingsbetweenthedoorandframeandbetweenthedoorandthreshold(orfloorifnothresholdexists).Emberscanbecomelodgedinopenings•betweenthedoorandframeandbetweenthedoorandthreshold(orfloorifnothresholdexists).Emberscanalsobeblownthroughtheopeningsintotheinteriorofthebuilding.Flames,convectiveorradiantheat,and•airbornefirebrandscanbreakglassinadoor.
Exterior Door Characteristics and RatingsTypesofexteriordoorsincludesolidentrancedoors,entrancedoorswithglassvisionpanels,slidingglassdoors,stormdoors,screendoors,garagedoors,andcellardoors.
Solidexteriordoorsaretypicallymadeofwoodormetal.Doorswithasolid,noncombustiblemineralcoreareclassifiedasfire-rateddoorsandareratedbyUnderwritersLaboratories(UL)accordingtothelengthoftimetheycanresistfire(ULStandard10C)(UL,1998).UL
Figure 1. Typesofexposurethatexteriordoorscanbesubjecttoinawildfire.
Welcome Welcome
Embers can become lodged in openings and separations
Radiant heat can shatter glass
Radiant heat and embers can ignite combustible materials and penetrate through openings
Page2of3 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 11 – Exterior Doors
classificationsforinteriorandexteriorfire-rateddoorsandtheirframesrangefrom3-hourto20-minuteratings.Exteriorfire-rateddoorsareavailablewitharatingof1½houror3/4hour.
Thefireratingfordoorsisintendedtoequalthree-fourthsofthefireratingofthesurroundingwall.Forexample,adoorwitha1½-hourratingisintendedtobeusedinawallwith2-hourrating,andadoorwitha3/4-hourratingisintendedtobeusedinawallwitha1-hourrating.However,adoorwithahigherfireratingmaybeused.
Guidance for New BuildingsIfafire-ratedexteriorwallisspecified(seeFactSheet#7,ExteriorWalls),specifyandinstalla•fire-rateddoorandframe.Asexplainedabove,theratingofthedoorandframeshouldbeatleastthree-fourthsoftheratingofthewall.Inaddition,specifyandinstallfire-ratedhardware.FollowtheguidancepertainingtodoorglassvisionpanelsandglassslidingdoorsinFact•Sheet#10,WindowsandSkylights.Toavoidembersandhotgasespenetratingtheinteriorofthebuildingbetweenthedoor•andthedoorframe,installadjustableweatherstrippingontheinteriorsideofthedoorframeandspecifyandinstallanautomaticdoorbottomorthresholdweatherstripping.TheweatherstrippinganddoorbottomshouldbetestedinaccordancewithULStandard10C.Weatherstrippingisrelativelyinexpensive(seeFigure2).Garagedoorsaretypicallymadeofwood,aluminum,orsteel•andareinsulatedornon-insulated.Unlikestandardegress/ingressdoors,garagedoorsarenotnormallytestedforfireresistance(seeFigure3).Toprotectthegaragedoorandentirebuilding,followtheguidancelistedbelow.
Specifyandinstallinsulated,metalgaragedoors. –
Toavoidembersandhotgasespenetratingthegarage, –specifyandinstallweatherstrippingthathasbeentestedinaccordancewithULStandard10Caroundtheentiregaragedoor.
Figure 2.Exampleofadjustableweatherstripping(FEMA577).
Fire-resistant weatherstripping
Noncombustible or fire-resistant trim
Insulated metal door
Figure 3.Agaragedoorwithnoncombustibleandfire-resistantcomponents.
Door
Adjustablejambweatherstrip
FS No. 11 – Exterior Doors HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of3
Forexteriortrimthatcoverstheopeningbetweenthedoorframeandexteriorwall,specifyand•installnoncombustibleorfire-resistantmaterialsuchasfire-retardant-treatedwoodorfiber-cementboard.
Guidance for Existing BuildingsAddweatherstrippingtodoors,asdescribedabove.•Replacevisionpanelsindoors,ifnecessary,asdescribedinFactSheet#10,Windowsand•Skylights.Replaceslidingglassdoorsand/orprotectwithshutters,asdescribedinFactSheet#10,•WindowsandSkylights.Replacewoodengaragedoors,particularlyiftheydonothaveasolidcore.•Replacewoodenegress/ingressdoorswithoutasolidcore,althoughegress/ingressdoorsare•oftenrelativelyfire-resistantcomparedtoothercomponentsofthebuildingandthereforenotnormallyahighpriorityforremediation.
ConsiderationsMetalandmetal-claddoorframescantransmitheatduringafire,andtheheatcanignitethesurroundingexteriorwallifthewallisnotconstructedtofire-resistantstandards,asnotedabove.Formoreinformation,seeFactSheet#7,ExteriorWalls.
EffectivenessAllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZonesexceptasfollows:Garagedoorsarenotnormallytestedforfireresistanceandmaynotprovideeffectivefire•resistanceinhighFireSeverityZones.Underveryhighheatorprolongedexposuretoheat,weatherstrippingmaterialcanmeltor•burn,loweringitseffectivenessinpreventingembersandhotgasesfromenteringtheinteriorofabuilding.
ResourcesFEMA.2007.Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High Winds:
Providing Protection to People and Buildings.RiskManagementSeries,FEMA577.http://www.fema.gov/library/viewRecord.do?id=2739.
SteelDoorInstitute(SDI).2001.Basic Fire Door Requirements. TechnicalDataSeriesSDI118-01. http://www.steeldoor.org/res/118.pdf).
UnderwritersLaboratory(UL).1998.ULStandard10C,PositivePressureFireTestsofDoorAssemblies.
FS No. 12 – Foundations HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of4
Foundations Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 12
PurposeToprovideguidanceonavoidingtheignitionoffoundationsbywindborneembersandconvectiveandradiantheatinwildfirezones.Guidancepertainstobothnewandexistingbuildings.
Foundation DesignsFoundationscanbeopenorclosed.Homesnormallyhaveonlyonetypeoffoundation,butsomehaveboth.
Closed FoundationInaclosedfoundation,thefoundationwallextendsfromthefootingtothefirstflooraroundtheperimeterofthebuilding.Thefoundationwallistypicallyabearingwall.Thebelow-gradeportionistypicallyconstructedofconcreteormasonry,butpreservative-treatedwoodcanalsobeused.Theabove-gradeportionmayalsobeconstructedofconcreteormasonry,oritmaybeastudwall(commonlyreferredtoasa“cripplewall”;seeFigure1).Thefoundationwallenclosesabasement,acrawlspace,orthesoilbelowaslab-on-grade.
Open FoundationInanopenfoundation,thebuildingissupportedbypilesorpiers,andthebottomofthefirst-floorframingisseveralfeetabove-grade(seeFigure2).Pilesandpiersareconstructedofconcrete,masonry,timber,orsteel.Someoftheareabelowthefirstfloormaybeenclosedwithwallsforanelevatorortocreateasmallstoragearea.1 Wood latticeisalsooftenplacedbetweenpiles/pierstoprovideaprivacyscreen(forexample,aroundcars parkedunderthebuilding).Manufacturedhousing 1 IfthehomeisinFloodHazardZoneV,seeTechnicalFactSheet27,EnclosuresandBreakawayWalls,inHome Builder’s
Guide to Coastal Construction,TechnicalFactSheetSeries(FEMA499).www.fema.gov/rebuild/mat/mat_fema499.shtm.
Figure 1.Aclosedfoundationwithacripplewall(FEMAfieldteam).
Figure 2.Anopenfoundation.
Page2of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 12 – Foundations
istypicallysupportedonanopenfoundation,butoftenanon-bearingwall(skirting)isinstalledaroundtheperimeterofthehomebetweengradeandthefloor.
Key Issues
Closed Foundation Directflame,embers,orhotgasescanenterthroughcrawlspaceventsorbreachedbasement•windows.Thecrawlspacewallorwallcoveringortheexposedportionofthebasementwallorwall•coveringcanbeignitedbydirectflame,embers,orhotgases.Oncethewallisignited,thefirecanpenetratethecrawlspaceorbasementandclimbuptheexteriorwall.Combustibleitemsstoredinbasementsorcrawlspaces(suchashouseholdgoodsincardboard•boxes)canbecomefuelinafire.
Open Foundation Theundersideofthefirstfloorcanbeignitedbydirectflame,embers,orhotgases.Whenpiles•orpiersareconstructedoftimber,thepile/pierisnormallythickenoughtoresistignition.SeeFactSheet#13,DecksandOtherAttachedStructures,forinformationonignitionresistanceasafunctionoftimberwidth.Woodlatticescreenscanbeignitedbydirectflame,embers,orhotgases.Latticescreens•oftentrapcombustibledebrissuchasleavesandpaper,increasingthepotentialforignition.Ignitionofalatticescreencanleadtoignitionoftheundersideofthefirstfloor.Wallsandwallcoveringsaroundenclosuressuchaselevatorshaftsandstorageareascanbe•ignitedbyembersorhotgases,leadingtoignitionoftheundersideofthefirstfloor.Combustibledebrisorstorageitems(suchasfirewoodorgasinacontainer)inanopen•foundationcanbeignited,leadingtoignitionoftheundersideofthefirstfloor.Skirtingaroundtheperimeterofmanufacturedhomescanbeignited,leadingtoignitionofthe•undersideofthefloorandspreadofafireuptheexteriorwall.
Guidance for New Buildings
Closed FoundationSeeFactSheet#7,ExteriorWalls,forguidanceonwallsandwallcoverings.•SeeFactSheet#8,Vents,forguidanceoncrawlspacevents.•SeeFactSheet#10,WindowsandSkylights,forguidanceonwindows.•
Open FoundationToavoidignitionofthefirst-floorframingmembers(joists)andfloordecking,sheaththeundersideoftheframingasfollows:
FS No. 12 – Foundations HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of4
Attach5/8-inchthickexteriortypeX•gypsumboardtotheundersideofthejoists.Forenergyconservation,installbattinsulationbetweenthejoists(seeFigure3).Attachfire-retardant-treatedplywood,•fiber-cementpanels,ormetalsidingpanelsoverthegypsumboard.Donotinstalllatticescreens.Ifscreens•areinstalled,usechain-linkfencingwithmetalprivacyslatsinsteadofwood.Forguidanceonenclosurewalls•aroundstorageareasandforskirtingonmanufacturedhomes,seeFactSheet#7,ExteriorWalls.Forguidanceonwindows,seeFactSheet#10,WindowsandSkylights.Forguidanceondoors,seeFactSheet#11,ExteriorDoors.
Guidance for Existing Buildings
Closed FoundationSeeFactSheet#7,ExteriorWalls,forguidanceonwallsandwallcoverings.•SeeFactSheet#8,Vents,forguidanceoncrawlspacevents.•SeeFactSheet#10,WindowsandSkylights,forguidanceonwindows.•
Open FoundationIfthefirst-floorframingmembersaretimbermemberslessthan3inchesthick(nominal)orif•thefloordeckingiscombustible,sheaththeundersideoftheframingasdescribedabove.Evaluatefloorbeamsandjoiststhatareconstructedofsteel(notcommoninresidential•construction).Dependingonavarietyofconditions,itmaybeprudenttosheaththeundersideoftheframingasdescribedaboveorprotectthesteelwithsuitablefireproofing.Removeexistinglatticescreensorreplacethemwithchain-linkfencingwithmetalprivacyslats.•Forguidanceonenclosurewallsaroundstorageareasandforskirtingonmanufactured•homes,seeFactSheet#7,ExteriorWalls.Forguidanceonwindows,seeFactSheet#10,WindowsandSkylights.Forguidanceondoors,seeFactSheet#11,ExteriorDoors.
ConsiderationsThehomeownershouldperiodicallyremovecombustibledebrisunderbuildingswithopen•foundations.
Figure 3.A5/8-inchtypeXgypsumboardattachedtotheundersideofthejoists.
5/8-inch type X gypsum
Joist
Subfloor
Exteriorcladding
Batt insulation
Page4of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 12 – Foundations
Thehomeownershouldnotstorecombustibleitemssuchasgasandfirewoodunderbuildings•withopenfoundations.Ifabuildingisexposedtoawildfire,anengineershouldevaluatethestructuralintegrityofthe•foundation.Inareaswheredryrotisaconcern,fire-retardant-treatedplywoodcanbeattachedoverthe•gypsumboardontheundersideofthefloorjoists,butplywoodisaffectedmorebyweatherelementsthanfiber-cementpanelsormetalsidingpanels.Ifthebuildingislocatedinafloodplain,asdesignatedbyFEMA’sNationalFloodInsurance•Program,criteriasetforthinTitle44CodeofFederalRegulationsPart60shouldbeconsidered.
EffectivenessAllmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZones.
ResourcesFEMA.2005.Home Builder’s Guide to Coastal Construction Technical Fact Sheet Series.
FEMA499.http://www.fema.gov/rebuild/mat/mat_fema499.shtm.
FEMA.2006.Recommended Residential Construction for the Gulf Coast: Building on Strong and Safe Foundations.FEMA550.www.fema.gov/library/viewRecord.do?id=1853.
Slack,P.2000.Firewise Construction Design and Materials.ColoradoStateForestService.
FS No. 13 – Decks and Other Attached Structures HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of4
Decks and Other Attached Structures Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 13
PurposeToprovideguidanceontheconstructionofdecksandotherattachedstructuresonhomesinwildfirezones.Otherattachedstructuresincludebalconies,porches,stairs,andramps.Allofthesestructurescanbeasourceoffuelduringawildfire.Ignitionbyflamesorfirebrandscanleadtoignitionoftheexteriorofthebuilding,resultinginsubstantialdamagetoortotallossofthebuilding.
Key IssuesDecksareoftenbuiltatthetopofaslopeinthedirectlineofthemostlikelyapproachofa•wildfire,puttingthesedecksatahighriskofignition.Buildinganddeckorientationisthereforeimportantinreducingtheriskofexposuretoawildfire(seeFactSheet#3,SelectingtheConstructionSite).Decksconstructedofdimensionedlumberarecombustibleandsubjecttoquickignition.•Embers,firebrands,andhotgasescanbecomelodgedortrappedunderdecksandother•attachedstructures,wherethestructuresattachtothebuilding,andinthegapsbetweenboarddecking.Theycanalsosettleagainstexteriorwallsandaccumulateatrailingedges.Allofthesethingsincreasetheriskofignitionofthesestructuresandignitionofthehome.
Guidance for New Decks and Other Attached Structures
SitingOrientdecksandotherattachedstructurestoavoidexposuretothepathofawildfire.Avoidconstructingthesestructuresnearheavilyvegetatedareasandtopographicfeaturessuchassteepslopes,gullies,canyons,saddles,ridgetops,andnarrowmountainpasses(seeFactSheet#3,SelectingtheConstructionSite).
Construction Materials Useheavytimberornoncombustiblematerials(seeFigure1).Thefollowingmaterialsarerecommended:Forcolumns,useaminimum6-inch• ×6-inchtimberor concreteblockorsteel.
Figure 1. Deckconstructedofheavytimber.
Decking: 3-inch nominal thickness
Columns: 6-inch x 6-inch
Joists: 3- or 4-inch nominal thickness
Railing: metal
Page2of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS 13 - Decks and Other Attached Structures
Forfloorjoistsandbeams,useheavytimber,3-inchto4-inchnominalthicknessfire-retardant-•treatedwood,orconcreteblockorsteelframing.Forrailings,useminimum3-inchnominalthicknessfire-retardant-treatedwood• ormetal,cables,ortemperedglass.Fordeckingandstairtreads,useexteriorfire-retardant-treatedwood,minimum3-inchnominal•thickness,orbrickorconcretepaversandasuitabledrainagematoverwooddeckingormetalgrates.Light,pouredconcretemayalsobeasuitabledeckcovering.
Duetoinsufficientdatacomparingtheperformanceofplasticandcompositematerialstoheavytimberdeckingwhenexposedtoflamesandheat,FEMAdoesnotrecommendtheuseofplasticorcompositedeckinginhighFireSeverityZones.However,theUniversityofCalifornia’sCenterforFireResearchandOutreach(Berkeley)hasconductedsometestingonplasticandcompositematerialsusedindecks.Resultsareasfollows:Plasticandcompositeproductswithchannelsontheundersideofthedeckingdegradedearly•whenexposedtounder-deckfires.Productswithhollowconstructionexhibitedboardcollapsewhenexposedtofirebrands.•Someproductswithasolidconstructionperformedsimilarlyto2-inchthicknominalwood•decking,butmanydidnotperformaswellasheavytimberdecking.
Moreinformationonthetestingisavailableathttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-4_Test_Standards.pdf.
Construction TechniquesIsolatetheattachedstructurebysurroundingitwith•noncombustiblematerialsuchasgravel,brick,orconcretepaverstopreventvegetativegrowthandreducefuelinawildfire(seeFigure2).Enclosetheundersideofthedeckwithfire-resistant•skirtingthatactsasashieldagainstembersandreducestheprobabilitythatradiatedandconvectedheatwillignitethedeck(seeFigure2).Topreventemberintrusioningapsbetweenthe•deckingandhome(suchasinoffsetledgerboardconstruction),coverthegapswith1/8-inchmetalscreening.Installflashingonledgerboardsthatareattachedwithoutgapstocreateabarriertoembersandpreventwaterfrompenetrating(seeFigure3).Coverexposedfloorframingattheundersideof•attachedstructureswithafire-resistantsoffitsuchasfiber-cementpanels.Thesoffitshouldhaveweepholeswithamaximumdiameterof1/4inchtoallowwaterthatleaksthroughthedeckingtodrainoutofthesoffitspace.
Figure 2. Deckisolatedbyapatio.
Surround deck with noncombustible patio
Enclose the deck with fire-resistant skirting
FS No. 13 – Decks and Other Attached Structures HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of4
Guidance for Existing Decks and Other Attached StructuresToenhancetheperformanceofexistingdecksandotherattachedstructures,thefollowingarerecommended:Replacecombustiblematerialswithnoncombustibleorfire-resistantmaterials.•Replacedimensionaltimberrailingswithrailingsconstructedoffire-resistantmaterialssuch•asmetal,temperedglass,cables,or3-inchnominalthicknessfire-retardant-treatedwood(seeFigure4).Whenthedeck,balcony,stairs,orrampcanaccommodateorbereinforcedtoaccommodate•additionalload,installbrickorconcretepaversandasuitabledrainagematovertheexistingdecking(seeFigure4).
Figure 3. Deckflashing.
Figure 4. Concretepaversoverexistingdeck.
Deck flashing
Deck joist
Exterior wall cladding
Exterior wall sheathing
Fiber-cement board
Flashing
Waterproof membrane
Concrete pavers
Existing deck
Existing joist
Gypsum soffit
Metal railing
Page4of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS 13 - Decks and Other Attached Structures
Constructdeckskirtingaroundthedeckusingfire-resistantornoncombustiblematerialsuch•asfiber-cementboardsand/orconstructapatioonthegroundaroundthedeck,stairs,orramp.Installasoffitattheundersideofbalconies,decks,stairlandings,orrampswhenskirtingisnot•installed(seeFigure4).
ConsiderationsMaintenanceandremovalofcombustible•debrisandvegetationaroundandunderdecksandotherattachedstructuresisakeyfactorinreducingvulnerabilitytoignitionduringawildfire(seeFigure5).Formoreinformationondefensiblespace,seeFactSheet#4,DefensibleSpace.Decksandotherattachedstructuresshould•bemaintainedbyreplacingdeterioratedcomponentsbeforetheylosetheirfire-resistance.Decksenclosedwithfire-resistantskirting•mustbeventedformoisturecontrol(seeFactSheet#8,Vents).
EffectivenessAllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZones.
ResourcesDecking:SFMStandard12-7A-4.2001CaliforniaReferencedStandardCodes(Part12,Title24,
C.C.R.).http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-4_Test_Standards.pdf.
UniversityofCaliforniaAgricultureandNaturalResources.FirePerformanceTesting:Decks.http://firecenter.berkeley.edu/quarles/deck_kit-SQ.pdf.
Figure 5. Combustibledebrisunderthisdeckignitedandledtothedestructionofthedeck.Althoughthesidingisnoncombustible,thefirespreadfromthedeckthroughawindowtotheinterior(firecenter.berkeley.edu).
FS No. 14 – Landscape Fences and Walls HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of3
Landscape Fences and Walls Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 14
PurposeToprovideguidanceaboutlandscapefencingandwallsthatareattachedtoornearbuildingsinwildfirezonestoreducethepotentialfordamagetothebuildingsfromawildfire.
Key Issues Landscapefencesandwallsfunctionas•physicalorvisualbarriersorarchitecturalstatements.Propertyownersdonotalwaysconsiderthepotentialthatlandscapefencesandwallscanhaveincontributingtothespreadofawildfire.Thecommonwoodenpost-and-boardfence•canbecomefuelforawildfire,especiallywhenthefenceisoldandweather-beaten.Thistypeoffencecanalsocollectembersandfirebrandsinawildfireandactasahorizontalladderfuelbyallowingthefiretotravelalongthefencetowardthemainbuilding(seeFigure1).Onceignited,afenceorwallconstructedof•combustiblematerialsthatisattachedtoornearabuildingcanignitethebuildingthroughradiantorconvectiveheatorbydirectflamecontact.
Guidance Usenoncombustiblematerialsforfencesandwalls.Fencesandwallsvaryinshape,size,and•constructionmaterials,allofwhichprovidevaryingdegreesofprotectionorriskinawildfire.Typicalmaterialsusedinfencesandwallsarewood,plastic,composite,metal,wire,concrete,stone,andmasonry.Ofthesematerials,woodisthemostcombustible,whileconcrete,stone,andmasonryarenoncombustible.
Wood. – Fencesthatareconstructedofwoodorhavewoodencomponentsarecombustibleandthereforeprovidenofireresistance.Combustiblematerialssuchassoftwoodsandpinetreatedwithpreservativesshouldbeavoidedifthefenceisattachedtothebuilding.Densehardwoodssuchasredoak,whiteoak,hickory/pecan,andwalnutaremorefire-resistantthanpinesandothersoftwoods.
Figure 1.Thegatethatwasattachedtothegarageatthecornerignitedandledthefiretothehome,causingthedamageseenhere(firecenter.berkeley.edu).
Page2of3 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 14 – Landscape Fences and Walls
Plastic. – Plasticfencesaremorefire-resistant,moredurable,andoftenstrongerthanwoodenfences,butplasticfencescanmeltinawildfirefromtemperaturesthatarebelowthemaximumawildfirecangenerate(seeFigure2).Metal. – Metalfencesaremorefire-resistantthanplasticfences.Wirefencessuchasbarbedwire,hogwire,andchainlinkhavelittleornoeffectonfirepassage.However,ifcombustiblematerialshaveaccumulatedinoraroundthefenceorthefencecontainscombustiblematerialssuchaswoodenposts,thefencecanactasahorizontalladderfuelbyallowingthefiretotravelalongthefencetowardthemainbuildingConcrete, stone, or masonry. – Concrete,stone,andmasonryfencesandwallsarenoncombustibleandcanactasabarriertoawildfirebydeflectingflamesawayfromabuilding,butthepassageofairborneembersandfirebrandswillnotbesignificantlyaltered.Thesematerialsarethemosteffectiveatminimizingthepotentialfordamagetoabuildingfromawildfire.
Avoidattachingfencesandwallsconstructedofcombustiblematerialstoabuilding.•Forfencesandwallsthatareattachedtoabuilding,ensurethatallcombustiblecomponents•areatleast10feetfromthebuildingtopreventheatandflamesfromignitingthebuilding.Avoidfencesthathavegaps,suchaswoodenslatfences,becauseairbornefirebrandscan•becometrappedinthegapsandignitethefence(seeFigure3).
Figure 2.Plasticfencescanmeltevenundermoderatewildfiretemperatures(FEMAfieldteam).
Figure 3. Keyguidanceforfences.
Avoid fences with gaps because airborne firebrands can become trapped in the gaps and ignite the fence
Clear combustible debris and vegetation near the fence regularly; vegetation growing on or around a fence can ignite, leading to ignition of the fence
FS No. 14 – Landscape Fences and Walls HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of3
ConsiderationsThephysicalconditionofthefenceorwallshouldbemaintained.•Combustibledebrisnearthefenceorwallshouldbeclearedregularly(seeFactSheet#4,•DefensibleSpace).Thetypeoflandscapevegetationthatisplantednexttoafenceorwallshouldbeconsidered,•andthevegetationshouldbemaintainedregularly.Unmanagedlandscapevegetationcanincreasetheprobabilitythatthefencewillignite,especiallyafencethatisconstructedofcombustiblematerials(seeFigure3).Formoreinformationondefensiblespace,seeFactSheet#4,DefensibleSpace.
EffectivenessMasonry,concrete,stone,metal,andhardwoodlandscapefencesandwallsareeffectiveinallFireSeverityZones.
ResourcesAmericanHardwoodInformationCenter.http://www.hardwoodinfo.com/species_guide/
brochure_44-45.pdf
CenterforFireResearchandOutreach.UniversityofCalifornia,Berkeley:CollegeofNaturalResources.http://firecenter.berkeley.edu/default.htm.
FiresafeCouncil.http://www.firesafecouncil.org/.
FirewiseCommunitiesProgram.http://www.firewise.org/.
FS No. 15 – Fire Sprinklers HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of4
Fire Sprinklers Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 15
PurposeToprovideguidanceontheinstallationofinteriorandexteriorfiresprinklersystemsonbuildingsinwildfirezones.Theguidancepertainstobothnewandexistingbuildings.
Key IssuesDuringawildfire,firebrandsandairbornedebriscanbreachwindows,andconvectiveheatand•emberscanpenetrateutilityopenings,gapsarounddoors,andotheropenings.Theinteriorofabuildingcanigniteevenwhentheexteriordoesnot.Firesprinklersarenotcommoninresidentialconstruction,buttheycanbeeffectiveinpreventingdamagefromawildfire.Exteriorbuildingcomponentsthatarecombustiblesuchasoverhangsandrecessedalcoves•cantrapembers,firebrands,andhotgases,leadingtoignitionofthebuilding.Exteriorsprinklerscanhelpextinguishflamesbeforethebuildinghasbeensubstantiallydamaged.Abuildingthathasignitedcanendangernearbybuildingsandcontributetothespreadofa•wildfire.Interiorandexteriorsprinklerscanpreventsubstantialdamagetothebuilding,protectnearbybuildings,andpreventthefirefromignitingnearbycombustiblevegetation.
Interior Fire Sprinklers
Common Misconception FactAllsprinklersinasystemactivatesimultaneously.
Onlysprinklerheadsthatareinanareaofhighheatareactivated.Typically,onlyoneortwoheadsactivateduringafire.Sprinklerheadsareactivatedonlybyheat,notbysmoke.
Sprinklerscanactivateaccidentally. AccordingtotheU.S.FireAdministration,only1in16millionsprinklerheadsactivatesaccidentally.
Waterdamagefromsprinklersismoreexpensivetorepairthandamagefromthefire.
Waterdamagefromsprinklersisusuallyconsiderablylessexpensivetorepairthandamagecausedbywaterfromfirehoses,smoke,andfire.Quick-responsesprinklersrelease8to24gallonsofwaterperminute,whilefirehosesrelease50to125gallonsperminute.
Interiorsprinklersystemsareobtrusiveandnotaestheticallypleasinginresidences.
Interiorfiresprinklersforsingle-familyresidencesaresmallerthantraditionalcommercialorindustrialfiresprinklersandcanbecoordinatedwithanyroomdécor.Sprinklerheadscomeinavarietyofstyles,models,andcolorsandcanbemountedflushwiththeceiling(seeFigure1)orconcealedbehindcovers.
Page2of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 15 – Fire Sprinklers
CharacteristicsI• nteriorfiresprinklersystemscandetectadevelopingfirequicklyandactivateautomatically.Systemsdonotrequiremanualintervention.Interiorsprinklersystemscanincludeawarningsystem•thatnotifiesoccupantsandemergencyresponsepersonnelofadevelopingfire.Interiorsprinklerscanbeinstalledduringnew•constructionorinanexistinghome.
GuidanceInstallingsprinklersinunoccupied,enclosedspaces•suchasatticsshouldbeconsideredbecausedoingsocanprovideadditionalprotectioniffirepenetratestheexteriorofthespace.Waterpressureandsupplymustbothbeadequateforaninteriorsprinklersystemtobe•effective.Wateristypicallysuppliedbythewatermainfromthemunicipalwatersupply.Duringawildfire,firefightingresourcesoftenexhausttheavailablewaterpressure.Ifexistingwaterpressureisinadequateorthesourceofwaterisawell,aholdingtankcanbeusedasawatersource.Toensurethatwaterisavailabletothesystemduringawildfire,apressurizedholdingtankshouldbeconsidered,evenifthestructureisconnectedtothemunicipalwatersupply.
ConsiderationsThemajorityofthecostofaninteriorsprinklersystemisassociatedwiththepipingmaterial.•Optionsformaterialsincludesteelalloys,copper,andfire-resistantplastics.Plasticpipingislessexpensivethansteelalloysandcopper,butitsmeltingpointisasmuchasfivetimeslowerthancopperpiping.Hazardinsuranceratesaretypicallydiscountedforhomeswithinteriorsprinklersystems.•Aninteriorsprinklersystemisrelativelyeasytoinstallduringnewconstruction.Thesystem•increasesthetotalcostofconstructionbyapproximately2percent;complexandmulti-storyinstallationsmayincreasethecostmore.Installinganinteriorsprinklersystemcanbedonewhentheroofisreplacedorupgraded,anddoingsomaycostlessthanstandardinstallation.Thecostofinstallinganinteriorsprinklersystemduringnewconstructionisabouthalfthecost•ofinstallingasysteminanexistingbuilding.
EffectivenessInternalsprinklersextinguishthefireatanearlystageandpreventsubstantialdamagefromheatandsmokeortotallossofthestructure.TheyareeffectiveinallFireSeverityZones.
Figure 1.Aconcealed,aestheticallypleasingfiresprinkler.
Sprinkler head ceiling cover
FS No. 15 – Fire Sprinklers HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of4
Exterior Fire Sprinklers
Characteristics Thepurposeofanexteriorfiresprinklersystemistosaturatetheexteriorofthebuilding.•Exteriorsprinklersystemscanbeinstalledduringnewconstructionoronexistingbuildings.•Theyarecommonlyinstalledontheroofalongtheridgelineorunderneaththeeavesandalongsoffits.Exteriorsprinklerscanbeactivatedautomaticallybylow-voltageheatdetectorsormanuallyby•occupantsbeforetheyevacuatethehome.Exteriorsprinklerscanincludeawarningsystemthatnotifiesoccupantsandemergency•responsepersonnelofadevelopingfire.Somelandscapesprinklersaredesignedandinstalledtoprovideprotectionfromawildfireto•landscapeareasimmediatelysurroundingabuilding.Anexteriorsprinklersystemcanbeinstalledsothatitissubstantiallyhiddenfromview.•
GuidanceExteriorsprinklersmountedonthebuildingcanbeconfiguredtousewaterpipingthroughtheatticorroofortousepipingontheexteriorofthestructure.Ifinteriorpipesareused,exteriorsprinklerscanbeinstalledinconjunctionwithinteriorsprinklers(seeFigure2).Astand-alonesystemthatincludesapressurizedholdingtankcanbeconsideredtoensureanadequatewatersupply.Seetheinformationaboutwatersupplyunderinteriorfiresprinklersabove.
ConsiderationsIfexteriorsprinklersareinstalledin•areaswherefreezingtemperaturesoccur,specialprovisionssuchasdrysprinklersarerequiredtopreventwaterinthepipingfromfreezingandrupturingit.Inadrysprinklersystem,theportionofpipingthatisvulnerabletofreezingisnotchargedwithwateruntilafireopensavalveandreleaseswaterintothepiping.Exteriorsprinklerscanprovideaddedprotectionwhenusedinconjunctionwithfire-resistant•constructionmaterials(seeFactSheets#5–14)anddefensiblespace(seeFactSheet#4,DefensibleSpace).Polymergels,ClassAfoamproducts,andotherlong-termfireretardantscanbeappliedto•structurespriortofireimpingementandprovidegreaterthermalprotectionthanwateralone.
Figure 2.Interiorandexteriorfiresprinklerscanbeinstalledinconjunctionwitheachother,suchasthissystemwithasprinklerintheatticandalongtheeave.
System is connected to the water main or a pressurized holding tank
Sprinklers can be installed in the attic and in the eaves
Page4of4 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 15 – Fire Sprinklers
Manyoftheseproductsareavailabletohomeownersinself-containedapplicationunitsandcanbeappliedwithanattachmenttoagardenhoseorintegratedintothehome’sexteriorsprinklersystems.
EffectivenessIfexteriorfiresprinklersrequiremanualactivation,occupantsmustactivatethesystem•expeditiouslyforthesystemtobeeffective.Highwindsthatarefrequentlyabyproductofmajorfireactivitycansignificantlydegradethe•effectivenessofanexteriorsprinklersystem.Manuallyappliedfire-protectionmaterialssuchasClassAfoamproductscanbeeffectiveif•timeisavailabletotreatthehome.Tobeeffective,thefire-protectionmaterialmustbeappliedwithinthetimeframeidentifiedbytheproductmanufacturer.
ResourcesFireSafety.gov.Residential Fire Sprinklers.http://www.firesafety.gov/citizens/sprinklers/index.
shtm.
NationalFireProtectionAssociation.2007.NFPA13D:Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes.http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=13D.
NationalFireSprinklerAssociation.Informationaboutresidentialsprinklersystems.http://www.nfsa.org.
FS No. 16 – Utilities HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page1of3
Utilities and Exterior Equipment Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 16
PurposeToprovideinformationaboutmeasuresthatcanbeimplementedtoprotectutilityconnectionstobuildingsandexteriorequipmentfromawildfire.Guidancepertainstobothnewandexistingbuildings.
DescriptionUtilitiesofalltypesthatpenetrateabuildingcanbeathreattoabuildinginawildfire.Exteriorequipment,suchassolarpanelsandreceiverdishes,canbevulnerabletodamagebythehightemperaturesgeneratedbyawildfire.Thefollowingutilitiesandequipmentareparticularlysusceptibletodamageinawildfire:
Electrical Utilities and Exterior Equipment Electricityisdeliveredtohomesthroughabovegroundconductorsanddroplines(themajorityofhomes)orthroughundergroundcables.Electricityisthenprovidedtoexteriorequipmentbycablesthatareconnectedtotheequipmentfrominsidethehome.
Fuel-related Utilities and Exterior Equipment Manyhomesusepressurizedgas(liquidpetroleumgas,suchaspropaneandbutane,ornaturalgas)orliquidfuel(fueloilorkerosene)forheating,hotwater,andcooking.Propaneandbutanearestoredinpressurizedvessels.Naturalgasisdeliveredthroughpressurizedpipesthatareconnectedtothehome.Liquidfuelisdeliveredtothehomebygravityfromon-sitestoragetanks.
Key Issues
GeneralExteriorequipmentoftencontainscombustible•componentsthatincreasetheriskofignitionoftheequipmentandthebuildingitisattachedto.Mostutilitiesandexteriorequipmentrequirepenetration•ofthebuildingenvelopeforductingandconduit(seeFigure1).Theopeningsmayallowheat,hotgases,andemberstoenterthebuildingandcauseignitionofcombustiblematerialsinthebuildinginterior.
Figure 1.Thegaparoundutilitypenetrationssuchasthisoneshouldbefilled.
Page2of3 09/08 HomeBuilder’sGuidetoConstructioninWildfireZones FS No. 16 – Utilities
Combustibledebriscancollectaroundexteriorequipment,increasingtheprobabilityofignition•oftheequipmentandbuilding.
Electrical Utilities and EquipmentWildfirescanaffectpowertransmissionbyconduction,convection,directflamecontact,and•heavysmoke.Wildfirescandamageequipmentsuchaspowerpolesandpowerlinesorcauseashortcircuitinthelines.Powersurgesandpoweroutagescausedbywindandfirecandamageelectricallypowered•equipmentinhomesthataremilesaway.Aswithanyelectricalpowersupply,waterwellpowersuppliesarevulnerableduringawildfire.•Waterwellsystemscanbeessentialtodomesticandfire-protectionneeds.Equipmentmountedonroofshasthesameignitionpotentialastheroofingassembly.•
Fuel-related Utilities and EquipmentExposed,combustibledeliverylinesarevulnerabletowildfire.Forexample,gasmetersare•vulnerabletowildfiredamageifpipeconnectionsincludearubberizedgasket.Pressurizedandliquidfuelsareflammableandexplosive.•Ventingoffuelunderpressuremaycausesignificantdamageortotaldestructionofabuilding,•dependingprimarilyonthelocationofthefuelcontainer.
Guidance
GeneralIfpossible,installutilityandequipmentconnectionsunderground,includingallentrypoints•intothebuilding.Ifautilityorequipmentconnectioncannotbeinstalledunderground,sealgapsand•penetrationsinexteriorwallsandroofswithfire-resistantcaulk,mortar,orfire-ratedexpandingfoam.Filllargegapswithintumescentorfire-protectivesheetsorpillows.Fire-resistantwrapmaybeusedaroundventilationfeaturesthatarebuiltintoandpenetrateexteriorwalls(suchasairconditioners).
Electrical Utilities and Equipment Shieldpowercablesandotherwiringwithnoncombustibleorfire-resistantmaterialstoprotect•thecablesandwiringfromconvection,radiation,andconductionheat,anddirectflamecontact.Usenoncombustibleorfire-resistantmaterialsformountingsystemsofroof-mounted•equipment.Usesurgeprotectorstoprotectsensitiveelectronicequipment.•
FS No. 16 – Utilities HomeBuilder’sGuidetoConstructioninWildfireZones 09/08 Page3of3
InstallClassAratedsolarcellsystems•forthegreatestprotection.SolarcellsystemsaretestedandratedunderthesameconditionsasroofingassembliesandareavailablewithClassAandClassCratings(seeFactSheet#5,Roofs).
Fuel-related Utilities and EquipmentBuryorshieldfuellinestoprotect•themfromradiation,conductionheat,anddirectflamecontact.Burypressurizedstoragevessels•underground(seeFigure2).Placefuelstoragevessels30feetfromthehomeandawayfromdownhillslopesandenclose•thembehindanoncombustiblemasonrywall.Shieldgasmetersfromhotairandgases,convectionandradiantheat,anddirectcontactby•flame,usingnoncombustiblematerialssuchasmasonryorconcrete.Ensurepressurizedstoragetankshaveapressurereliefvalve.Astheoutsidetemperature•risesinawildfire,thepressureinsidethetankcanincrease.Whenthepressuresettingisexceeded,thevalvewillopenandrelievethepressure,preventinganexplosion.
ConsiderationsReplacingpipes,cables,andotherinstallationscandamagesealantsforwallpenetrations.•Fire-resistantsealantsandnoncombustiblemortarmustberemovedandreplacedeachtimeacableorpipeisreinstalled.Usingdefensiblespaceforthelocationofutilitiesandexteriorequipment(forexample,electric•waterpumps,fueltanks)shouldbeconsidered(seeFactSheet#4,DefensibleSpace).
EffectivenessAllmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZones.
ResourcesFire-resistantexpandingfoamstandards:ASTME814,UL1479,BS476,Part20.
Pressurereliefvalvestandards:ASME(AmericanSocietyofMechanicalEngineers)Boiler&PressureVesselCode,SectionVIIIDivision1andSectionI.
Fuel storage tank
Filler pipeVent
Buried fuel lines
Figure 2.Buriedfuelstoragetank.
FS No. 17 – Community Infrastructure Home Builder’s Guide to Construction in Wildfire Zones 09/08 Page 1 of 5
Community Infrastructure Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 17
PurposeToprovideguidanceaboutneighborhoodandcommunity-widefire-safepracticesthatwillenhancefireprotectioninwildfirezones.Guidancepertainstocommunityinfrastructure,includingroadsusedforevacuationroutesandemergencyaccess,andemergencywatersupply.Althoughahomebuildermaynothavecontrolovertheseelements,communityofficialsandhomeownersshouldbeawareofmeasuresthatcanbetakenonacommunity-widebasistoincreasethechancesofanentireneighborhood’ssurvivalinawildfire.
BackgroundPoorlydesignedorinadequateinfrastructurecanhamperfire-suppressioneffortsandput•citizensandfirefightersatrisk.Reducingtheriskofwildfiredamageanddestructionrequiresimplementingmeasuresbeyondthoseinvolvinganindividualbuildingorparcel.Itisalsoessentialtoenhancemitigationmeasuresattheneighborhoodandcommunitylevels,whichwilleffectivelyexpandthezoneofprotectionbeyondtheindividualparcelorbuilding.
Thelocalfireagency,stateforestryornaturalresourcesdepartments,thelocaloffice•ofemergencymanagement,orotherlocalorganizationsshouldbecontactedtoobtaininformationaboutthehazardsandrisksinanarea.
Key Issues Emergencyresponsevehiclesmayneedtoaccessawildfireareaatthesametimeevacuation•trafficisleavingthearea.Firefightersneedsafeaccessalongroadstoreachthewildfireandaccesswaterresources.
Visiblestreetsignsandpropertyaddressesprovidefirefighterswithcriticalresponseand•locationinformation.Propertyaddressesareoftennotvisible,andaroadnamemayoccurmorethanonceinajurisdiction.
Wildlandfuelsandlandscapevegetationalongroadscanplacefirefightersinextremely•hazardoussituations.
Waterresourcesforwildfiresuppressionarevitalandneedtobeaccessible.•
Guidance for Roads and DrivewaysRoadsshouldbewideenoughtoallowevacuationandemergencyvehiclessimultaneous•access.Minimumwidthis20feetforaccessroadsand12feetfordriveways(seeFigure1).
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Themaximumgradeofroadsanddriveways•shouldbedeterminedbythelocaljurisdictionbutingeneralshouldnotexceedagradeof16percent.
Roadsanddrivewaysshouldprovide•sufficientverticalclearancetoallowfor largeemergencyvehicles.Theminimum is13.6feet(seeFigure1).
Roadsshouldsupportaminimum•of40,000poundstoallowforheavyemergencyvehicles.
Appropriatesignage,includingbutnot•limitedtoweightandverticalclearancelimitationsandone-wayroadandsingle-laneconditions,shouldbepostedandfullyvisibleonnoncombustiblesignsandposts.
Gatedaccessfromapublicroadwayshould•besetbackfromtheroadwayatadistancethatissufficienttoallowemergencyequipmenttoclearthetrafficlane.Adistanceof50feetshouldbeadequateformostequipment(seeFigure2).
Turnaroundsshouldbeattheendofroads•andondrivewaysthatarelongerthan150feet.Theminimuminsideturningradiusshouldnotbelessthan30feet,andtheoutsideturningradiusforaturnaroundshouldbe45feetfromthecenterlineoftheroad.Ifahammerhead/”T”isused,thetopofthe“T”shouldhaveaminimumlengthof60feet(seeFigure3).
Roadsanddrivewaysshouldprovide•all-weatheraccess,whichmayrequireasphaltorconcretesurfacing.
Address and Signage Publicandprivateroadsandstreetsshouldbeidentifiedbyanameornumberthrougha•consistentjurisdiction-widesystemthatprovidesforsequencedorpatternednumbering and/ornon-duplicatingnamingwithineachjurisdiction.
Figure 1.Roadwithadequatewidthforemergencyvehicles.
Figure 3. Thetopofthe“T”usedforaturnaround(AnchorPointGroup,Boulder,CO).
Figure 2.Gatedaccesswitha50-footsetbackthatallowsemergencyvehiclestoclearthetrafficlane.
13.6-footminimum clearance 20-foot minimum
width for access roads
12-foot minimum width for driveways
50 fe
et
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Sizeofletters,numbers,andsymbolsforstreetandroadsignsshouldhaveaminimum4-inch•letterheightand1/2-inchstroke,bereflective,andcontrastwiththebackgroundcolorofthesign.Thesignandsignsupportshouldbeconstructedofnoncombustiblematerials.
Streetandroadsignsshouldbevisibleandlegiblefrombothdirectionsofvehicletravelfora•distanceofatleast100feetandbemountedataheightof7feetfromtheroadsurfacetothebottomofthesign.
Allbuildingsshouldhaveapermanentlypostedaddressateachdrivewayentranceandshould•bevisiblefrombothdirectionsoftravelalongtheaccessroad.
FuelModificationReducingthevolumeanddensityof•combustiblevegetationreducestheintensityofwildfire.Strategicfuelmodificationalongaccessandegressroutesincreasessafetyforemergencyfireequipmentandevacuatingcitizens(seeFigure4).
Areassuchasgolfcourses,schools,•andlargeparkinglotsshouldbelabeledassafetyzonesforcitizensunabletoevacuateorforfirefighters.Itiscriticallyimportantthattheseareasbeevaluatedbyfireprofessionalsbeforeasafetyzoneisdesignated.
Guidance for Emergency Water Supply Community-widewatersuppliesneedtobeavailableandaccessible.•
Signsshouldbeprovidedindicatingaccesstoeachwatersource.•
Vegetationshouldbemaintainedateachwatersourcetoallowsafeaccesstothesource.•
Water Tanks and Pressure SystemsSomecommunitywatersystemsusetanksandcisternstostoreemergencywatersupplies.Individualpropertiesmaybesuppliedwithpotablewaterthroughon-sitewellsorlimiteddistributionsystemsduetothedispersednatureofthecommunityorthecostofinstallingamajorwaterdeliverysystem.Watertanksshouldbeconstructedofhighlyfire-resistantmaterialssuchassteel,concrete,or•ferrocement.Fiberglasstanksmaybeplacedunderground.Allcisternsorwatertanksusedfor
Figure 4.Exampleofamapdepictingareasforplannedfuelmodificationalongevacuationroutes/fireaccessroads(AnchorPointGroup,Boulder,CO).
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emergenciesshouldhaveafiredepartmentconnection.Thelocaljurisdictionmayspecifythesizeandtypeoffiredepartmentconnection.
Pressurizedsystemswithhydrantsshouldconformtothelocaljurisdiction’srequirementsor•recommendationsforspacing,flow,andpressure.
InstallationshouldmeetNationalFireProtectionAssociationstandardsattheminimum.•
Dry HydrantsManyruralareasdonothaveaccesstothepressurizedhydrantsthatarecommoninlargercommunitiesforfirefighting.Whenpressurizedsystemsarenotavailable,dryhydrantsarerecommended.Dryhydrantsarearelativelyinexpensivewaytoprovideareadysourceofwaterforfirefighting
Adryhydrantisanon-pressurizedpipesystemthatallowsfireequipmentaccesstoanearbysourceofwatersuchasalake,stream,pond,residentialpool,orcisternwithaminimumwaterdepthof2feet,orawatersourcesuchasatankthatisnotdirectlyaccessibletoafireapparatus(seeFigure5).
ConsiderationsThefire-suppressioncapabilitiesinthearea,asdiscussedabove,shouldbeconsideredwhenselectingaconstructionsite(seeFactSheet#3,SelectingtheConstructionSite).
Formoreinformationaboutinfrastructure,seeFEMA’sWildfireHazardMitigationHandbookforPublic Facilities.
EffectivenessTheeffectivenessoftherecommendedmeasuresvariessignificantly,dependingontheinfrastructureelementsthatarepresentinthecommunity.
Figure 5. Dryhydrantdesigns.
2-foot minimum
Anticipated low-water level
Normal waterline elevation
Installation below frost depth
18-footmaximum
2 feet
Strainer
Design using two 45-degree elbows
Design using two 90-degree elbows
FS No. 17 – Community Infrastructure Home Builder’s Guide to Construction in Wildfire Zones 09/08 Page 5 of 5
ResourcesCaliforniaAdministrativeCodeTitle14,Division1.5,§1270–1276.
InternationalCodeCouncil.2006.2006 International Wildland-Urban Interface Code.
NationalFireProtectionAssociation.2001.NFPA Standard 1142: Standard on Water Supplies for Suburban and Rural Fire Fighting.
NaturalResourcesConservationService.DryHydrantDesignDrawings.http://www.sc.nrcs.usda.gov/technical/dryhydrant.html.
Lagucki,T.andK.Mancl.FireProtectioninRuralAreas:DryHydrantsforPonds.TheOhioStateUniversityFactSheet:Food,AgriculturalandBiologicalEngineering.http://ohioline.osu.edu/aex-fact/0422.html.
RanchoSantaFe[California]FireProtectionDistrict.StandardforDriveways,Dead-EndsandLoopedAccessWays.http://www.rsf-fire.org/prevention/access_requirements.asp.Includesinformationonfireaccessroadandfirehydrantspecifications(specificationsandordinancesmaybedifferentforotherstates,cities,anddistricts).
StateofMinnesota.TheDryHydrantConcept.http://files.dnr.state.mn.us/assistance/backyard/firewise/dryhydrant_advantages.pdf.
Winter,A.,S.Holman,S.Kett,andR.Dolan.2006.Taylor[Florida]CommunityWildfireProtectionPlan. http://www.fl-dof.com/publications/fire_pdfs/taylor_fl_cwpp_complete.pdf.Includesimprovementstowildlandfireresponse,suchasinstallationofdryhydrantsandupgradestocommunicationsequipment.