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This document was prepared by
URS Group, Inc.
200 Orchard Ridge Drive, Suite 101
Gaithersburg, 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 OKeefe, California Department of Forestry and Fire Protection (San Bernardino Unit)
Ken Worman, Governors 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
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FS No. 1 Wildland/Urban Interface Construction HomeBuildersGuidetoCon structionin WildreZones 09/08 Page1 of 5
Wildland/UrbanInterface Construction
Home Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 1
Purpose
Toprovideinformationaboutwildrebehaviorandrecommendationsforbuildingdesignand
constructionmethodsinthewildland/urbaninterface.Implementationoftherecommended
designandconstructionmethodscangreatlyincreasethechancesofabuildingssurvivalina
wildre(seeFigure1).
Background
Wildresareacommon,natural,andessentialoccurrenceintheforests,woodlands,
brushlands,andgrasslandsoftheUnitedStates.Whenconditionsareacceptable,re
professionalsuseretorevitalizetheecosystemandreduceaccumulatedvegetationthatcan
fuelawildreundercertainconditions.
Althoughtheseverityandtimingofreseasonsvarywidelyfromregiontoregion,wildresoften
poseathreattolives,property,andresources.Duringanaveragereseason,hundredsof
homesaredamagedordestroyedbywildre,andinextremereconditions,thousandsofhomes
canbedamagedordestroyed.Severereweatherinareaswithsignicantamountsofwildland
fuelscanleadtoextremerebehavior.
WildlandfuelsvarythroughouttheUnitedStates.InthePacicnorthwestandtheLakeStates,
forestsarethepredominatewildlandfuel.InsouthernCalifornia,chaparralbrushpredominates.
Theplainsstateshavegrassandoakwoodlands,NewJerseyhasPineBarrens,andthe
southeasthaspineandhardwoodforests.
Figure 1. Ahomeinthewildland/
urbaninterfacethatsurvived
awildre(AnchorPointGroup,
Boulder,CO).
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Page2of5 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 1 Wildland/Urban Interface Construction
Wildrescandamagebuildingsthroughdirectamecontact,convection(heatthatrisesfrom
areandcreatesasmokecolumn),conduction(heatthattransfersthroughmaterialsuchas
metalroofsandrailings),andradiation(heatfromarenexttothebuilding).Wildrescanalso
createburningembersthatriseinthesmokecolumnandfallonbuildings.Firebrands(large
piecesofwind-driven,burningmaterial)canbeblownthroughwindowsorlodgedagainsta
buildingandleadtoignitionofthebuilding.
Traditionaleffortstoprotectbuildingsfromwildreshavefocusedonghtingtherebefore
itreachesthebuildings.Withtheexpansionofresidentialconstructionintopreviously
undevelopedforestsandwildlands,morebuildingsarenowatriskfromwildres.Fighting
orsuppressingthereisoftendifcultorimpractical;buildingsmustthereforealsobe
constructedtobere-resistant.Nobuildingcanbecompletelyreproof,butimplementingthe
recommendationsthataredescribedintheseFactSheetsshouldgreatlyreducethepotentialfor
damagetoabuildingandgreatlyincreaseitschanceofsurvival.
Construction in the Wildland/Urban InterfaceThefollowingfactorsaffecttheprobabilitythatabuildingwillsurviveawildre:
Topographyandweather
Defensiblespace
Buildingenvelope
Communityinfrastructure
Topography and Weather
Wildresgenerallyfolloworaredrivenbyterrainandweather.Buildingsatthetopofacanyon
orridgeline,atmid-slope,orinaravinehaveahigherriskfordamagefromawildreduetotheinteractionofthesefeatureswithstrongwindsthanatlocationssuchasvalleybottoms.When
aconstructionsiteisselected,thetopographicfeaturesonandsurroundingasiteshouldbe
evaluatedfortheirpotentialcontributiontotheexposureofabuildingtoawildre.Abuildings
congurationandlocationonasiteshouldbepredicatedonminimizingtheriskfromthese
topographicfeatures.
SeeFactSheet#3,SelectingtheConstructionSite.
Defensible Space
Wildrestravelquicklyinareaswherevegetationisdryandabundant.Adefensiblespace
aroundabuildingcanimprovetheprobabilitythatthebuildingwillsurviveawildre.Adefensible
spaceisanareawherecombustiblematerial,includingvegetation,hasbeentreated,clearedor
modiedtoslowtherateandintensityofanadvancingwildreandtocreateasaferareaforre-
suppressionoperationstooccur.Buildingssurroundedbyzonesofnon-vegetatedareasorareas
populatedbyre-resistantvegetationaremorelikelytosurvive.
SeeFactSheet#4,DefensibleSpace.
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FS No. 1 Wildland/Urban Interface Construction HomeBuildersGuidetoCon structionin WildreZones 09/08 Page3 of 5
Building Envelope
Duringawildre,combustibleexteriorbuildingcomponentssuchasroofcoverings,siding,and
deckscanignite,leadingtoseveredamagetoortotallossofthebuilding.Therefore,theuse
ofnoncombustibleorre-resistantmaterialsshouldbeconsideredforexteriorcomponents.
Figure2showsthecomponentsofthebuildingenvelope.
Alsocriticalisthecongurationofthenoncombustibleorre-resistantmaterials.Unless
constructionmeasuresthatprovideprotectionfromawildreareimplemented,heatand
emberscanpenetratethebuildingenvelopeatvents,unsealedmechanicalorelectrical
openings,andthroughwindowsbrokenbyheatorwind-blownrebrands.Whentheseopenings
arepenetrated,thebuildingcanburnfromtheinsideout.
Iftheenvelopehasbeendesignedandconstructedtobere-resistant,boththeexteriorand
interiorofthebuildingwillbemorecapableofresistingawildrelongenoughforthedangerto
passorforreghterstoarrive.
SeeFactSheets#5through#16.
Community Infrastructure
Ahomethathasbeenconstructedtobere-resistantandhasadefensiblespacemaynot
besufcienttopreventdamagefromawildre.Survivingawildremayalsodependon
infrastructuresuchaslocalwaterresourcesforreghtingandroadsthataredesignedfor
emergencyvehicleaccess.Thebuildingsiteshouldalsohaveadequateinfrastructuretoensure
accessforreghtingcrews.
SeeFactSheet#17,CommunityInfrastructure.
Figure 2. Thebuildingenvelope.
Building Envelope
Vents
Garage door Exterior door
Siding
Roof Deck
Fence
Windows
Eaves
Foundation
Gutters
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Page4of5 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 1 Wildland/Urban Interface Construction
Prioritizing Fire-resistant
Construction Techniques
Theriskofwildrevariesgreatlyanddepends
onlocalfuels,weather,andtopography.Therisk
atabuildingsitemustbedeterminedbeforethe
appropriatedesignandconstructionmethods
foraneworexistingbuildingcanbeselected
andthemeasurescanbeprioritized.
Hazard and Risk Assessments
Thefoundationofanaccuratehazardandrisk
assessmentisinformationonwildrefuels,
weather,topography,assetsatrisk,andthe
probabilityofawildreoccurrence.Asitecan
beinanareawithaveryhighhazard(highlyvulnerabletowildre)buthavealowriskof
wildre,suchasasiteatahighaltitude.This
informationcanbeusedtodesignateFire
SeverityZones.Thezonescanthenbegiven
arating,fromlowtoextreme,asshownin
Figure3.
Ahazardandriskassessmentcanhelp
determinethelevelofmitigationthatisneededforabuilding.Theassessment,whichcanbe
conductedataregional,state,orlocallevel,needstobebothcredibleandprofessionalto
ensurethattheanalysisisaccurate,comprehensive,andveriable.Someregional,state,andlocalagenciesproducehazardriskmapssimilartothoseshowninFigures3and4.Thesemaps
maybefoundinstate,tribal,andlocalagencyhazardmitigationplansthathavebeenapproved
bytheFederalEmergencyManagementAgency(FEMA).
New Buildings
Fornewconstruction,FEMArecommendsfollowingthedesignandconstructionguidance
providedinthisseriesofFactSheets.
Existing Buildings
FEMArecognizesthatitmaynotbenanciallypossibleforthehomeownertoimplementall
ofthemeasuresthatarerecommendedinthisseriesofFactSheets.FEMArecommends
thathomeownersconsultwithlocalreandbuildingcodeofcialsorotherremanagement
specialiststoperformavulnerabilityassessmentanddevelopacustomized,prioritizedlistof
recommendationsforremedialworkondefensiblespaceandthebuildingenvelope.
Helpfulinformationaboutthevulnerabilitiesofthebuildingenvelopeisavailableathttp://
recenter.berkeley.edu/default.htm.TheHomeownersWildreAssessmentsurveyonthis
Figure 3. Exampleofarehazardratingmap.
Firehazardratingscanhelpdeterminethe
levelofmitigationthatisnecessaryforwildre
management(AnchorPointGroup,Boulder,CO).
http://firecenter.berkeley.edu/default.htmhttp://firecenter.berkeley.edu/default.htmhttp://firecenter.berkeley.edu/default.htmhttp://firecenter.berkeley.edu/default.htmhttp://firecenter.berkeley.edu/default.htm -
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FS No. 1 Wildland/Urban Interface Construction HomeBuildersGuidetoCon structionin WildreZones 09/08 Page5 of 5
websiteisahelpfultoolthatpropertyownerscanusetolearnaboutthespecicrisksa
particularbuildinghasandthemeasuresthatcanbetakentoaddressthem.
Construction Standards
Manycommunitiesenforceregulationsregardingwhereandhowbuildingsmaybesited,
designed,andconstructed.Theregulations,however,refertominimumstandards.Individual
propertyownershavetheoptiontoexceedthesestandards,anddoingsoveryoftenincreases
theprobabilitythatthehomewillsurviveawildre.
Resources
CenterforFireResearchandOutreach.UniversityofCalifornia,Berkeley:CollegeofNatural
Resources.http://recenter.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-re-can-your-home-take-heat/.
Underwood,J.1995.Fire-ResistantDetails.Fine Homebuilding96:9093.http://www.
taunton.com/nehomebuilding/how-to/articles/re-resistant-details.aspx.
Figure 4. Exampleofafuelmodel
map.Fuelmodelsthatdemonstrate
thelocationofcombustible
vegetationarepartofthefoundation
forrebehaviorcalculations(Anchor
PointGroup,Boulder,CO).
http://firecenter.berkeley.edu/default.htmhttp://firecenter.berkeley.edu/default.htmhttp://www.redding.com/news/2008/Feb/16/trial-fire-can-your-home-take-heat/http://www.taunton.com/finehomebuilding/how-to/articles/fire-resistant-details.aspxhttp://www.taunton.com/finehomebuilding/how-to/articles/fire-resistant-details.aspxhttp://www.taunton.com/finehomebuilding/how-to/articles/fire-resistant-details.aspxhttp://www.taunton.com/finehomebuilding/how-to/articles/fire-resistant-details.aspxhttp://www.redding.com/news/2008/Feb/16/trial-fire-can-your-home-take-heat/http://firecenter.berkeley.edu/default.htm -
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FS No. 2 Summary of Recommendations HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of5
Summary of WildreConstruction
RecommendationsHome Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 2
Stateandlocalcodesshouldincluderequirementsforwildremitigationforbothnew
constructionandupgradestoexistingbuildingsinwildrezones.Inareaswherebuildingsare
particularlyvulnerabletotheriskofwildre,implementingmeasuresthatexceedthecodescan
improvetheprobabilitythatabuildingwillsurviveawildre.
TheUnifed Hazard Mitigation Assistance GuidanceandtheWildfre Mitigation Policyforthe
HazardMitigationGrantProgram(HMGP)andPre-DisasterMitigation(PDM)Programprovide
informationonwhichactivitiesareconsideredeligibleforfundingbytheFederalEmergency
ManagementAgency(FEMA)forwildremitigationactivities.
ThisseriesofTechnicalFactSheetsfromFEMAprovideinformationabouthowtominimizethe
potentialfordamagetoordestructionofbuildingsinwildrezonesfromwildres.Theinformation
pertainstobothnewandexistingbuildings.
TheFactSheetsareavailableontheFEMAwebsite( www.fema.gov)asAdobePortableDocument
Format(PDF)les.YoumusthaveAdobeReadertoviewthePDFles.ThelatestversionofAdobe
Readerisrecommendedandcanbedownloadedfrom www.adobe.com.
ThefollowingisasummaryoftherecommendationscontainedinFactSheets#3through#17.
Fact Sheet #3: Selecting the Construction Site
Topographicfeaturessuchasslopesandcanyons,local
vegetation,andweathercangreatlyinuencewildrebehavior.
Homebuildersshouldconsiderthesefactorscarefullywhen
selectingaconstructionsite
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Page2of5 09/08 HomeBuildersGuidetoConstructioninWildreZone FS No. 2 Summary of Recommendations
Fact Sheet #5: Roofs
Ofthecomponentsofthebuildingenvelope,theroofisthemost
vulnerableinawildrebecauseofitssizeandorientation.The
probabilitythatahomewillsurviveawildreisgreatlyinuenced
bythecomponentsoftheroofassembly.ClassAratedroofassemblieswithnoncombustiblecoveringsarerecommended.
Fact Sheet #6: Eaves, Overhangs, and Softs
Windborneembersandconvectiveandradiantheatcanbe
trappedneareavesandsofts,whichcanigniteifnotconstructed
ofnoncombustibleorre-resistantmaterials.Eaveswithshortoverhangsandatsoftswithaminimumofa1-hourre-
resistanceratingarerecommended.
Fact Sheet #7: Exterior Walls
Howwellexteriorwallsareabletoresistawildredependslargely
onthematerialsusedtoconstructthewall.Exteriorwallcoverings
thatarenoncombustibleorre-resistantandnotsusceptibleto
meltingarerecommended.Aminimumre-resistanceratingof
1hourforthewallassemblyisrecommended
Fact Sheet #4: Defensible Space
Creatingadefensiblespace,whichcanoftenbedonebythe
homeowner,isrecommended.Adefensiblespaceisanarea
aroundahomeinwhichvegetation,debris,andothertypes
ofcombustiblefuelshavebeentreated,cleared,orreduced.
Landscapemanagementcreatesabarrierbetweenahomeandawildre.Withoutadefensiblespace,reghtersmaynotattemptto
protectthehomebecausedoingsowouldbetoohazardous.
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FS No. 2 Summary of Recommendations HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of5
Fact Sheet #9: Gutters and Downspouts
Combustibledebrissuchasleavesandpineneedlescanbecome
trappedingutters.Thedebriscanbeignitedbyyingembersor
rebrandsduringawildre,andtherecanspreadtotheroof.
Noncombustibleleafguardsoverguttersandguttersconstructedofnoncombustiblematerialsarerecommended.
Fact Sheet #10: Windows and Skylights
Flames,rebrands,radiantheat,andfailedframescancause
glazingtobreakorotherwisefail.Glazing(glass,plastic,or
translucentmaterial)thatfailsallowseasypassageofembersandhotgasesintotheinteriorofabuilding.Insulatedglazingunitsare
recommended.Thereratingofwindowassembliesshouldbe
commensuratewiththereratingofthewall.
Fact Sheet #11: Exterior Doors
Combustibledoorsandframescanbeignitedinawildre,and
openingsbetweenthedoorandframeandglassinthedoorcan
bepenetratedbyames,hotgases,orembers.Thereratingof
thedoorshouldbecommensuratewiththereratingofthewall.
Weatherstrippingandnoncombustibleorre-resistanttrimare
recommended.
Fact Sheet #8: Vents
Embersandhotgasescanbeblownorpulledintoventopenings
andenteratticspaces,crawlspaces,andductwork,leadingto
ignitionoftheinteriorofthebuilding.Ventsthatareaminimum
of10feetfrompropertylinesandotherbuildings,constructedof
metalproducts,andhavecorrosive-resistantmetalmeshscreensarerecommended.
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Page4of5 09/08 HomeBuildersGuidetoConstructioninWildreZone FS No. 2 Summary of Recommendations
Fact Sheet #14: Landscape Fences and Walls
Onceignited,afenceconstructedofcombustiblematerialsthatis
attachedtoornearabuildingcanignitethebuilding.Fencesand
wallsconstructedofnoncombustiblematerialssuchasconcrete,stone,andmasonryarerecommended.Attachingafenceor
walltothebuildingshouldbeavoidedunlessthefenceorwallis
constructedofnoncombustiblematerials
Fact Sheet #15: Fire Sprinklers
Theinteriorofabuildingcanignitefromawildreevenwhenthe
exteriordoesnot.Interiorandexteriorresprinklerscanprevent
substantialdamagetothebuilding,protectnearbybuildings,and
preventtherefromignitingnearbycombustiblevegetation.
Fact Sheet #13: Decks and Other Attached Structures
Embers,rebrands,andhotgasescanbecometrappedunder
decksandotherattachedstructures.Decksconstructedofheavy
timberornoncombustiblematerialsarerecommended.Isolating
theattachedstructurebysurroundingitwithnoncombustiblematerialsuchasgravel,brick,andconcretepavers,andenclosing
theundersideofthedeckwithre-resistantskirtingarealso
recommended.
Fact Sheet #12: Foundations
Embers,rebrands,andhotgasescanignitecombustible
foundationwallsandpenetratecrawlspaceventsandbreached
basementwindows.Walls,vents,andwindowsinclosed
foundationsshouldbeconstructedinaccordancewiththe
guidanceintheseFactSheets.Inhomeswithopenfoundations,protectingtheundersideoftheoorstructurewithre-resistant
materialsisrecommended.
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FS No. 2 Summary of Recommendations HomeBuildersGuidetoConstructioninWildreZones 09/08 Page5of5
Fact Sheet #17: Community Infrastructure
Accessroadsanddrivewaysthatarewideandstrongenough
toaccommodateemergencyvehiclesandprovideaccessfor
reghtingeffortsarenecessary.Waterresourcesforwildre
suppressionmustbeaccessible.Roadsandwatersourcesshouldbewellmarkedonsignsconstructedofre-resistantmaterialsfor
easeofusebyemergencyresponsepersonnel.
Fact Sheet #16: Utilities and Exterior Equipment
Mostutilitiesrequirepenetrationofthebuildingsenvelope
forductingandconduit.Utilityconnectionsshouldbeinstalled
underground,ifpossible,andgapsandpenetrationsinexterior
wallsandroofsshouldbesealedwithre-resistantproducts.Fuel
shouldbestoredundergroundorsurroundedbyanoncombustiblebarrier.
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FS No. 3 Selecting the Construction Site HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of4
Selecting theConstruction Site
Home Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 3
Purpose
Tohelppropertyownerswhoplantobuildhomesorotherstructuresinwildrezonesunderstand
therelationshipbetweenwildrebehaviorandfuels,weather,andtopographysotheycanselect
constructionsitesthatminimizethepotentialfordamagefromwildres.Theguidancelistedin
thisFactSheetappliesonlytonewbuildings.
Key Issues
Wildresspreadmorequicklyonupslopedterrainthan
onlevelterrain(seeFigure1).Topographicfeaturessuch
asslopes,saddles,ridges,andcanyonscantherefore
inuencewildrebehavior(seebelowforadescriptionof
thesefeatures).Theinteractionofwindandradiantheat
withsomeofthefeaturesisalsoanimportantfactorin
wildrebehavior.
Thedirectionaslopefacesinuencesthegrowthof
vegetation,andvegetationinuenceswildrebehavior
becauseitprovidesfuelforthewildre.
Implementingthere-mitigationmeasuresdescribedintheotherFactSheetscannotentirelyoffsetthepotential
fordamagefromawildreathigh-risksiteswith
topographicandvegetationfeaturesthatcancontribute
toextremerebehavior.
Topography
Sloped terrain. Wind-drivenwildresfollowwinddirectionandareminimallyinuencedby
topography.Intheabsenceofastrongwind,wildrefollowstopography,burningprimarily
upslopeandup-canyon.Wildresspreadupslopequicklybecauseheatrisesandpreheats
andignitesfuelssuchasbuildingsandvegetation.
Saddles. Whereavalleycrossesaridge,
asaddleiscreatedbetweentwopeaks
(seeFigure2).Saddlesactaswindfunnels
andareoneofthemosthazardous
locationsforhomesintermsofwildre.
Figure 1.Firespreadsmorequicklyon
upslopedterrainthanonlevelterrain.
Fuel,topography,andweatherarethethree
principalenvironmentalelementsthataffect
wildrebehavior.Fuels(vegetation)and
localtopographyshouldbeconsideredwhen
choosingasiteforahometoincreasethe
chancethehomewillsurviveawildre.
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Page2of4 09/08 HomeBuilder s G uidetoConstructioninWildreZones FS No. 3 Selecting the Construction Site
Ridgetops and hilltops. Wind speeds onridgetopsandhilltopscanbeunpredictable
buttendtobehigherthanthoseinthe
surroundinglowerareasbecauseofthe
higherelevationandbecausewindspeed
increasesasitowsoverabruptchangesintopography.Buildingsintheselocations
canhave360-degreedownhillexposureto
wildre.
Canyons. Awildreatthebottomofa
vegetatedcanyoncanleadtoextremely
hazardousconditionsupslope.Acanyon
actslikeachimney,collectinghotgases
anddirectingsuperheatedconvectionand
radiantheatupslope.Canyonsfunnelwinds
(seeFigure3)thatcanfanareandleadtoextremerebehavior(rapidspreadofthe
wildreandignitionofanentirearea).An
entirecanyoncanpre-heatfromrisinghotair
andgasesandexplodeinames,creatinga
restorm.
Vegetation
Vegetationactsasafuelforwildres.Vegetationbothonandadjacenttoasitecanaffect
theprobabilityofdamagetoabuildingfromawildre.Characteristicsofvegetationsuchas
density,continuity,andtypecaninuencewildrebehavior(seeFactSheet#4,Defensible
Space,formoreinformation).
South-andwest-facingslopesgenerallyretainlessmoisture,producelessvegetation,and
dryoutearlierintheyearthannorth-andeast-facingslopes.Firesondryerslopestendto
ignitemoreeasily,travelmorerapidly,andburnoutfasteraslightfuelsareconsumed.The
moreheavilyvegetatedmoistslopeshavealowerpotentialforignitionbutcansustainamore
intensereoflongerdurationthandryslopes.
Guidance
Byunderstandinghowtopographyandvegetationcaninuencewildrebehavior,propertyownerscanselectconstructionsitesinwildrezonesthatreducethepotentialfordamagetoabuilding
fromawildre.Followingtheguidancelistedbelowcanincreasetheprobabilitythatabuildingwill
surviveawildre.
Avoidselectingaconstructionsitealongagullyorinanarrowcanyon.
Avoidselectingaconstructionsiteinoradjacenttoasaddleornarrowmountainpass.
Avoidconstructingahomeadjacenttooronasteepslope.Ifaridgetopsiteisselected,choose
Figure 2. Windbehavioroverasaddle.
Figure 3.Windbehaviorthroughacanyon.
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FS No. 3 Selecting the Construction Site HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of4
anareathatallowsforaminimum
50-footsetbackfromwildland
vegetationonthedownslopeside
(seeFigure4).Increasethesetback
atsiteswithheavierfuelssuchasin
aforestedenvironment.ImplementthemeasuresinFactSheet#4,
DefensibleSpace;FactSheet#12,
Foundations;andFactSheet#13,
Decks.
Orientthenarrowestwallofthe
buildingtowardthelikelypathof
awildretominimizetheriskofstructuralignition.Orientthebuildingbasedonwindand
fuelssothatdebris,embers,andrebrandsdonotaccumulatenexttothebuildingswalls,
especiallyneartheinsidecornersofentriesandotheroff-setwalls.
Minimizethenumberofwindowsonthesideofthebuildingfacingthelikelypathofawildretoreducetheriskofradiantheatorrebrandsandyingdebrisbreakingthewindows,allowing
theretoenterthebuilding.
Considerations
Considerthevegetationcharacteristicsonandadjacenttothesiteincludingdensity,continuity,
andtype.Ifthesitehasheavy,continuousvegetation,avegetationmanagementplanmaybe
neededtoreducethehazard.Creatingadefensiblespacecanenhancereresistance(see
FactSheet#4,DefensibleSpace).
Consideraccesstothehome.Steepdrivewaysandnarrowroadscanlimitaccessibilitybyre-ghtingequipment(seeFactSheet#17,CommunityInfrastructure).
Evaluatethevulnerabilitytoreofneighboringproperties.Iftheneighboringpropertieshave
rehazardsbuttheneighborsareunwillingtocooperateindevelopingamutualdefensible
space,considerthatinformationinselectingre-resistancemeasuresforthebuilding.
Effectiveness
Theeffectivenessoftherecommendedmeasurescanvarysignicantly,dependingonthe
interactionoffuels,weather,topography,andwildrebehavior.
Resources
Barkley,Y.C.,C.Schnepf,andJ.Cohen.2005. Protecting and Landscaping Homes in the
Wildland/Urban Interface.StationBulletin#67.Moscow,Idaho:IdahoForest,Wildlifeand
RangeExperimentStation.www.treesearch.fs.fed.us/pubs/22257.
CaliforniaDepartmentofForestryandFireProtection.www.re.ca.gov.
CaliforniaFireSafeCouncil. www.resafecouncil.org.
Figure 4.Exampleofsetbackfromwildlandvegetation.
50feet
http://www.treesearch.fs.fed.us/pubs/22257http://www.treesearch.fs.fed.us/pubs/22257http://www.fire.ca.gov/http://www.fire.ca.gov/http://www.treesearch.fs.fed.us/pubs/22257http://www.fire.ca.gov/ -
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Page4of4 09/08 HomeBuilder s G uidetoConstructioninWildreZones FS No. 3 Selecting the Construction Site
FirewiseCommunitiesProgram. www.rewise.org/newsroom/faq.htm.
NationalWildreCoordinatingGroup. www.nwcg.gov.
Slack,P.2000.Firewise Construction Design and Materials.ColoradoStateForestService.
http://www.firewise.org/newsroom/faq.htmhttp://www.firewise.org/newsroom/faq.htmhttp://www.nwcg.gov/http://www.nwcg.gov/http://www.nwcg.gov/http://www.firewise.org/newsroom/faq.htm -
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FS No. 4 Defensible Space HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of4
Defensible SpaceHome Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 4
PurposeToprovideinformationaboutcreatingadefensiblespacetoreducethepotentialfordamageto
homesfromwildres.Guidancepertainstobothnewandexistingbuildings.
Background
Adefensiblespaceisanareaaroundabuildinginwhichvegetation,debris,andothertypesof
combustiblefuelshavebeentreated,cleared,orreducedtoslowthespreadofretoandfrom
thebuilding.Informationaboutlocalvegetation,weather,andtopographyisusedtodetermine
theFireSeverityZoneofanarea,whichcanhelpdeterminethemosteffectivedesignofa
defensiblespace.
Adefensiblespaceisoneofthemostcost-effectivewaystoprotectabuildingfromawildreand
canoftenbecreatedbythepropertyowner.
Key Issues
Wildlandvegetationsuchasgrass,brush,andtimbercanbeextremelycombustible.The
vegetationcanburnwithgreatintensityandproducerebrandsandburningembersthatcan
becomewind-drivenhazards.
Landscapevegetationcanbeascombustibleaswildlandvegetation.
Combustibleplantshavethesecharacteristics:
Volatileresinsandoils(generallyaromatic
whencrushed)
Narrowleavesorlong,thinneedlessuchas
coniferneedles
Waxyorfuzzyleaves
Anaccumulationofdeadleavesandtwigson
andundertheplant
Looseorpaperybark
Awildrecanmovehorizontallyfromshrubto
shrubandtreetotree.
Awildrecanalsotravelverticallyfromthegroundupintothetreetops,resultingina
catastrophiccrownre(arethatcantravelatanincrediblepacethroughthetopofaforest).
Figure1showsarethatisspreadingverticallyfromgrassestoshrubstolowbranches.
Accessorybuildingsandstructuresandotheritemscommonlyfoundinyardsthataremade
Figure 1.Firespreadsverticallythroughvegetation(AnchorPointGroup,Boulder,CO).
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Page2of4 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 4 Defensible Space
ofcombustiblematerialscanalsoputan
otherwisere-resistantbuildingatriskof
ignitionanddestruction.
Combustiblevegetationandmaterialsarounda
building(seeFigure2)can:
Increasetheriskofbuildingignition
Restrictthespacenecessarytoprovide
reghtersarelativelysafeplacetoprotect
abuilding
Increasethechancethatabuildingonre
willigniteadjacentwildlands
Guidance
Assessboththehorizontalandverticalaspectsofvegetationwhendesigningthedefensible
space.
Topreventthehorizontalspreadofwildre,thinshrubsandtreessothecrownsdonot
intersectandthereisspacebetweenindividualshrubsandtrees.
Topreventtheverticalspreadofwildre,keepthelowesttreebranchesprunedandtrimmed
tomaintainverticalseparationfromthetopofshrubsandgrassestothelowesttreebranches.
Theverticaldistanceneededwillvarysignicantly,dependingonthespeciesoftreeand
compositionoftheunderstory.
Createthreeconcentriczonesaroundthebuilding(seeFigure3).Zone1,thezoneclosest
tothebuilding,normallyhasthegreatestneedforfuelmodicationwithprogressivelyless
modicationintheothertwozones.ThehighertheFireSeverityZone,thelargertheconcentriczonesshouldbe.Consultthelocalorstatereagencyforassistance.Thethreezonesare
discussedfurtherbelow.
Zone 1
EliminateallcombustiblematerialsinZone1(within30feetofthehome)suchasre-prone
vegetation,rewoodstacks,combustiblepatiofurniture,umbrellas,anddimensionedlumber
decking(seeFigure4).Desirablesubstitutionsincludeirrigatedgrass,rockgardens,stone
patios,metalpatiofurniture,andnoncombustibledecking(seeFactSheet#13,Decksand
OtherAttachedStructures).
Beforereseasonbegins,removecombustiblelitteronroofsandguttersandtrimtreebranchesthatoverhangtheroofandchimney(seeFactSheet#9,Gutters).
Zone 2
EnsurethatZone2includesonlyindividualandwell-spacedclumpsoftreesandshrubs
and/orafewislandsofvegetationthataresurroundedbyareaswithnoncombustible
materials.
Figure 2.Combustiblematerialsadjacenttoabuildingcreateahazard(AnchorPointGroup,
Boulder,CO).
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FS No. 4 Defensible Space HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of4
Usehardscapefeaturessuchasdrivewaysandpavedorgravelwalkwaysorpatiostocreate
rebreaksthroughouttheyard.
Plantre-resistant,low-volumevegetationthatretainsmoisturewellandneedsminimum
maintenancesuchaspruningandremovingdeadanddyingbranches.
Separateauxiliarystructuressuchasadetachedgarage,pumphouse,pergola,andutilityshed
fromthehomebyatleast50feet.Increasethedistanceifthestructureisusedforthestorage
ofcombustiblematerials.
Complywithrecommendedconstructionpracticesrelatedtoreresistanceforauxiliary
structures.SeeFactSheets#5to#16forguidanceonplanninganddesigningastructureina
wildrezone.
Ensurethatpatiofurnitureiseithermadeof
noncombustiblematerialsuchasmetaloris
atleast30feetawayfromthebuilding.Store
patiofurnitureinalocationthatisprotected
fromignitionbyawildre.
Placewoodpilesatleast30feetfromthe
buildingandstorethewoodinavegetation-
freezonesuchasagraveledarea.
Storefueltanksawayfromastructureatthe
minimumdistancethatisrequiredbycode
orgreater(seeFactSheet#16,Utilities)and
placeundergroundoronanoncombustible
pad.
Figure 4.AnoncombustiblegroundcoverinZone1
helpedthishomesurviveawildre(AnchorPoint
Group,Boulder,CO).
Figure 3.Thethreeconcentriczonesofdefensiblespace.
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Page4of4 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 4 Defensible Space
Zone 3
Reducefuelsthatarefartherthan100feetfromthebuildingbythinningandpruningvegetation
horizontallyandverticallyasdiscussedabove.ThinningandpruninginZone3canbemore
limitedthaninZone2.ThegoalsinZone3aretoimprovethehealthofthewildlandsandhelp
slowanapproachingwildre.Zone3isalsoanaesthetictransitionbetweenthemoreheavily
modiedZone2andtheunmodiedsurroundings.
Considerations
Consultthelocalorstatereagencyorqualiedremanagementspecialistaboutcodes,
requirements,andstandardsrelatedtodefensiblespace.Codes,requirements,andstandards
normallyrepresenttheminimumthatshouldbedone.Considerationshouldbegivento
providingenhancedprotectionmeasuresbeyondtheminimumrecommendedorrequired.
Maintainingadefensiblespacerequiresroutinemaintenanceofvegetation,whichincludes
pruningandremovingdeadbranchesandleaves.Characteristicsoflow-maintenance
plantsare:
Drought-resistant
Pest-resistant
Nativetothearea
Noninvasive
Slow-growing
Wind-resistant
Sustainablewithoutsupplementalfertilization
Vegetationmodicationmustbeperformedincompliancewithlocal,state,andfederalenvironmentalregulations.
Effectiveness
AllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZones.
Resources
Barkley,Y.C.,C.Schnepf,andJ.Cohen.2005. Protecting and Landscaping Homes in the
Wildland/Urban Interface.StationBulletin#67.Moscow,Idaho:IdahoForest,Wildlifeand
RangeExperimentStation.www.treesearch.fs.fed.us/pubs/22257.
FirewiseCommunitiesProgram. www.rewise.org/newsroom/faq.htm.
NationalFireProtectionAssociation(NFPA)1144:StandardforReducingStructureIgnition
HazardsfromWildlandFire.2008. http://dnrc.mt.gov/forestry/Fire/Prevention/documents/
WUIrewrite/NFPA1144.pdf.
NationalWildreCoordinatingGroup. www.nwcg.gov.
http://www.treesearch.fs.fed.us/pubs/22257http://www.firewise.org/newsroom/faq.htmhttp://www.firewise.org/newsroom/faq.htmhttp://dnrc.mt.gov/forestry/Fire/Prevention/documents/WUIrewrite/NFPA1144.pdfhttp://dnrc.mt.gov/forestry/Fire/Prevention/documents/WUIrewrite/NFPA1144.pdfhttp://www.nwcg.gov/http://www.nwcg.gov/http://www.nwcg.gov/http://dnrc.mt.gov/forestry/Fire/Prevention/documents/WUIrewrite/NFPA1144.pdfhttp://dnrc.mt.gov/forestry/Fire/Prevention/documents/WUIrewrite/NFPA1144.pdfhttp://www.firewise.org/newsroom/faq.htmhttp://www.treesearch.fs.fed.us/pubs/22257 -
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FS No. 5 Roofs HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of5
RoofsHome Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 5
PurposeToprovidegeneralguidanceonthedesignandconstructionofroofassembliesonbuildingsin
wildrezones.Guidancepertainstobothnewandexistingbuildings.
Key Issues
Roofassembliesarethemostvulnerable
componentofthebuildingenvelopein
awildrebecauseoftheirhorizontal
orientationandsize.
Embersandrebrandscanignitetheroofcovering,otherroofcomponents,anddebris
ontheroof.Oncetheroofhasignited,there
commonlypropagatesintotheinteriorofthe
building,resultinginsubstantialdamageto
ortotallossofthebuilding.
Theprobabilitythatahomewillsurviveawildreisgreatlyinuencedbythecomponentsofthe
roofassembly.Thetypeandarrangementofthecomponentsgoverntheirpotentialforignition
andtheirpropensitytotransferheatintotheinteriorofthebuilding.
Thecomplexityoftheroofsshapealsoinuencesthepotentialforignition.Aroofwithvalleys
androof/wallintersectionswherecombustibledebrissuchasleavesandneedlescancollect
hasmorepotentialforignitionthanaroofwithoutthem.
Fire-rated Roof Assemblies
Theresistanceofroofassembliestoexternalre
isratedbytheAmericanSocietyofTestingand
Materials(ASTM),usingtestmethodE108.The
methodincludesmeasurementsofthesurface
spreadofame,theabilityoftheroofassemblyto
resistrepenetrationfromtheexteriorofthebuildingtotheundersideoftheroofdeck,andthepotential
fortheroofcoveringtodevelopyingbrandsofburningmaterial.Roofassembliesarerated
ClassA(highestrating),B,orC.Assembliesthatfailthetest(donotmeettheClassA,B,orC
criteria)areunrated.
ClassAprovidesthegreatestdegreeofreresistance,butthereisarangeofprotectionwithin
theClassArating.Forexample,someClassAratedassemblieshavenoncombustibleroof
Roof covering: Theexteriorroofcoveror
skinoftheroofassembly(e.g.,shingles,
tiles,slate,metalpanels,roofmembrane).
Roof assembly:Anassemblyofinteractingroofcomponents,includingtheroofdeck,
vaporretarder(ifpresent),insulation
(ifpresent),insulationcoverboards(if
present),andtheroofcovering.
ASTME108testconditionsdonot
replicateactualwildreconditions.In
manycases,actualwildreexposures
aremuchmoreseverethanthose
inducedduringthetesting.
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Page2of5 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 5 Roofs
coverings(suchasclayorconcretetilesandmetalpanels),whileothershavecombustible
coverings(suchasasphaltshinglesandlow-slopemembranes).
Guidance for New Buildings
ManytypesofroofassembliesareratedClassA.RecommendationsforvariouscomponentsofroofassembliesthatareratedClassAareprovidedbelow.
Steep-slope Roof: Covering
Asteep-sloperoofisaroofwithaslopegreaterthan3:12.Thefollowingdesignandinstallation
practicesarerecommended:
Tile. Clayandconcretetilearenoncombustibleandbecauseoftheirrelativelylargethermal
mass,retardthetransferofheat.Lightweighttileproductsareavailable,butnormal-weight
tilesarerecommendedbecauseoftheirgreatermass.Iftilesareinstalledoverwoodbattens,
embersmaybeblownunderthetilesandignitethebattens.Fire-retardant-treatedbattensare
thereforerecommended.Iftileisused,thefollowingarealsorecommended:
Eaves, hips, and ridges. Emberscanbeblown
undertilesattheeaves,hips,andridges.
Birdscanbuildnestsinthespacebetween
theunderlaymentandthebottomofthetilesif
thespaceisaccessible,providingcombustible
debristhatcanbeignitedbyembers.Installing
birdstopsateavesandfullymortaringhipsand
ridgesarebothrecommendedtoavoidthe
accumulationofdebrisundertilesandtokeep
embersout(seeFigure1).
Valleys. Unlessspecialmetalashingis
installed,combustibledebriscanaccumulatein
valleysandthenunderthetiles.Flatandplain
tilesshouldbespeciedtobetightlybuttedtoformaclosedvalley,andpiecesofmetal
ashingshouldbeinstalledundereachtilecoursealongthevalleycenterline.Forproled
tile,leadorexibleashingshouldbeused,asrecommendedbythetilemanufacturer
(seeFigure2).
Metal shingles and panels. Metalshinglesandpanelsarenoncombustible,buttheyreadily
transferheat.Iftheyareinstalledoverwoodbattens,re-retardant-treatedbattensshouldbe
speciedandinstalled.Ifshinglesorpanelsareinstalledoverwooddecking,5/8-inchgypsum
Figure 1.Abirdstopattheeave.
Birdstops prevent debris
from accumulating under tiles
OnlyClassAratedroofassemblies
arerecommendedforhomesin
wildrezones.
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FS No. 5 Roofs HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of5
roofboardcomplyingwithASTMC11771shouldbe
installedoverthedecking.
Fiberglass-reinforced asphalt shingles. Althougha
roofassemblythathasberglass-reinforcedasphalt
shinglescanberatedasClassA,theseshingles
containcombustiblematerial(e.g.,asphalt).Ifthistypeofshingleisused,a5/8-inchgypsumroof
boardthatcomplieswithASTMC1177overthe
wooddeckingshouldbeinstalledforenhanced
protectionofthedecking.Careneedstobetaken
whentheshinglesarenailedthatthenailsarenot
overdriven.
Wood shingles and shakes . Roofassembliesthat
havewoodshinglesandshakescanberated
ClassAiftheshinglesorshakesarere-retardant-
treatedandaspeciccapsheetunderlaymentisinstalled.Withouttheunderlayment,themaximumratingisClassB.Notethatwhenshinglesorshakesarere-retardant-treated,they
cannotbeimpregnatedwithpreservativetreatment.
Ifre-retardant-treatedshinglesorshakesareinstalledoverwooddecking,installing
a5/8-inchgypsumroofboardthatcomplieswithASTMC1177overthedeckingis
recommendedinadditiontothespecialunderlaymentthatisrequiredtoachievea
ClassArating.
Steep-slope Roof: Underlayment
Emberscanbeblownundersometypesofsteep-
slopecoveringssuchastile,slate,andmetal
shinglesandpanels.Iftilesbecomedislodgedor
cracked,emberscanlandontheunderlayment
below(seeFigure3).Installinganunderlayment
thathasenhancedreresistanceisrecommended
toprovideprotectionfromembersthatreachthe
underlayment.
Anexampleofanenhancedunderlaymentisa
mineral-surfacecapsheetthatisratedforusein
aClassAratedassembly.2
Ifamineral-surfacecapsheetisusedundermetalpanelsorshingles,
measuresshouldbetakentopreventthemetalfrombearingdirectlyonthecapsheetandthe
capsheetfromabradingthemetal(therebymakingthemetalsusceptibletocorrosion).
1Boardsthatare5/8-inchthickaretypeX(specialre-resistant).Boardsthatare1/2-inchand1/4-inchthickare
nottypeX.2Althoughcapsheetsarenormallythenishedsurfaceofabuilt-upormodiedbituminousroofcovering,acapsheetcan
alsobeusedasanunderlayment.
Figure 3. Displacedtilesallowemberentry.
Figure 2.Specialvalleyashingtoavoid
debrisaccumulationbetweenandbelow
tiles(photographcourtesyofMonierLifetile).
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Page4of5 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 5 Roofs
Steep-slope Roof: Decking
Mosthomeshaveroofdecksthatareconstructedofwood,typicallyplywoodororientedstrand
board.Fire-retardant-treateddeckingcanbespeciedtoavoidignitionofthedeck.Formore
protection,5/8-inchgypsumroofboardscanbespeciedinadditiontothere-retardant-
treateddeck.
Althoughnotcommoninhomes,noncombustibledeckssuchassteelorconcrete,including
concretetoppingoversteeldecking,canbespecied.Inadditiontobeingnoncombustible,
concretedecksoffergreatresistancetoheattransferandrepenetrationthroughthedeckfrom
theexterior.
Low-slope Roof: Covering and Underlayment
Low-sloperoofshaveslopeslessthan3:12.
Avarietyoflow-sloperoofcoveringsand
assembliesareavailablewithaClassA
rating.
Ifalow-slopeassemblyisselected,the
followingrecommendationsshouldbe
followed:
Polyisocyanurateroofinsulationshould
bespecied(seeFigure4).
A5/8-inchgypsumroofboardthat
complieswithASTMC1177immediately
belowtheroofmembrane(seeFigure4)
shouldbespecied.
Forenhancedreresistance,inadditiontotheaboverecommendations,theroofmembrane
shouldbeprotectedwithheavyweight(i.e.,17poundspersquarefootminimum)concrete
pavers(seeFigure5).
Ifpaversareplacedoverabuilt-upormodiedbitumenmembrane,alayerofextruded
polystyreneinsulation(intendedforprotectedmembranesystems)overthemembrane
shouldbespecied.
Figure 5.Concretepaversover
membrane(FEMA55).
Mortar-facedextruded polystyrene
Roofparapet
Extrudedpolystyrene
Concretepavers
Membrane
Polyisocyanurateinsulation
Roofmembrane
5/8-inch
gypsum board
Roof deck
Figure 4. Componentsofalow-slopedroof.
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FS No. 5 Roofs HomeBuildersGuidetoConstructioninWildreZones 09/08 Page5of5
Additionally,forsmooth-surfacedbuilt-upandmodiedbitumenmembranes,asheet
ofpolyethylene(minimumof4mils)shouldbespeciedbetweenthemembraneand
polystyrenetokeepthepolystyrenefrombondingtothemembrane.
Toprotectthebaseashings,amortar-facedextrudedpolystyreneboardshouldbeinstalled
overthebaseashing(seeFigure5).
Low-slope Roof: DeckingRoofdeckingdesignandconstructionarethesameforsteep-slopeandlow-sloperoofs.Seethe
discussionundersteep-sloperoofsabove.
Guidance for Existing Buildings
ForhomeownerswithroofassembliesthatarenotClassArated,theonlylong-term,reliable
waytoreduceroofvulnerabilitytowildreistoreroof.Reroongnormallyinvolvesremovingthe
materialsabovetheroofdeckandreplacingthemwithnewmaterials.Therecommendationsthat
arelistedabovefornewbuildingsareapplicabletoreroongdesignandinstallation.
RoofassembliesthathavewoodshinglesorshakesandarenotratedClassAandroofswith
organic-reinforcedasphaltshinglesarevulnerabletoawildre.Thesetypesofroofsshouldbe
replacedassoonaspossible.
Considerations
Thehomeownershouldhaveroofdebrisremovedfromtheroofsurfaceandguttersregularly.
Agingdoesnotaffecttheignitionpotentialoftile.However,someroofcoverings,suchaswood
orberglass-reinforcedasphaltshingles,becomemoresusceptibletoignitionastheyage.The
roofcoveringshouldbereplacedbeforedeteriorationofthecoveringsignicantlydegrades
resistancetoignition.
Birdstopsshouldbeinspectedannuallytoensurethattheyhavenotfallenoutofplace.
Forrecommendationsonvents,seeFactSheet#8,Vents.
Forrecommendationsonguttersanddownspouts,seeFactSheet#9,Guttersand
Downspouts.
Effectiveness
AllmitigationmeasuresrecommendedinthisFactSheetareeffectiveinallFireSeverityZones.
Resources
AmericanSocietyofTestingMaterials(ASTM).2007.Standard Test Methods for Fire Tests of Roof
Coverings.ASTME108-07a.
FEMA.2003.Coastal Construction Manual.FEMA55.
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FS No. 6 Eaves, Overhangs, and Softs HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of3
Eaves, Overhangs,and Softs
Home Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 6
Purpose
Toprovideguidanceonthedesignandconstructionofeaves,overhangs,andsoftsinwildre
zones.Theguidancepertainstobothnewandexistingbuildings.
Key Issues
Windborneembers,convectiveheat,andradiantheatcanbetrappedunderoverhangsand
intheupperportionofexteriorwalls.Overhangsandwallscanigniteifnotconstructedof
noncombustibleorre-resistantmaterials.
Typicalconstructionmaterialsforeaves,overhangs,andsoftsarenotre-resistantandare
thereforesusceptibletoignitionbyembersandhotgases.
Onceaneave,overhang,orsofthasignited,recanspreadontotheroof,intotheattic,or
ontoandthroughtheexteriorwall.
Softsnormallyhaveventsaspartoftheatticventilationsystem.Unprotectedventscanallow
embersandhotgasestoentertheattic(seeFactSheet#8,Vents).
Typical Design and Construction
Eaves.Eavesarelocatedatthedown-slopeedgeofaslopedroofandserveasthetransition
betweentheroofandfascia/wall.Aneavetypicallyhasametaledgeashingandgutterthatare
attachedtoawoodfasciatrimboard.
Overhangs.Overhangsareextensionsoftheroofbeyondtheexteriorwall(i.e.,thejoists,
rafters,ortrussesandthedeckingtheysupport
cantileverpastthewall).Anoverhangprotects
theupperportionofthewallthatitisattached
tofromrainfall,anditalsoshadesthewindows
underitfromthesun.Overhangscanbeopen,
inwhichthetrusses/raftersanddeckingareexposed(seeFigure1),orenclosedbyasoft.
Softs.Asoftenclosestheundersideofsloped-
orat-roofoverhangs.Softsarecommonly
constructedfromber-cementpanels,metal
panels,stucco,vinylpanels,orwoodsheathing.
Metalpanels,untreatedwoodpanels,andvinyl
Attic vents
Figure 1. Anopenoverhang.Theexposedtimber
raftersanddeckingaresusceptibletoignition,and
embersandhotgasescanentertheatticthrough
unprotectedvents.
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Page2of3 09/08 HomeBuildersGuidetoConstructioninWildr eZones FS No. 6 Eaves, Overhangs, and Softs
panelsarevulnerabletodamagefromwildres.Metalpanelsconductheatandcandistortand
allowpassageofembersandhotgases.Untreatedwoodpanelscanignite,andvinylpanelscan
meltandfallaway.
Guidance for New Buildings
Considerdesigningthebuildingwithout
overhangs(seeFigure2)toavoidthere-
relatedproblemsassociatedwithsoftsor
minimizeasmuchaspossibletheextent
oftheoverhangtoreducethepotentialfor
entrapmentofembersandhotgases.
Ifnooverhangsorshortoverhangsare
unacceptablebecauseofaestheticsor
adesiretoprotectthewallsfromrainfall
orwindowsfromthesun,implementthefollowingrecommendedmeasures:
Encloseoverhangswithsoftsthathave
aminimum1-hourre-resistancerating
topreventembersandhotgasesfrommakingcontactwiththejoists,raftersortrusses,or
theundersideoftheroofdecking.
Useat,horizontalsofts(seeFigure3)insteadofattachingthesoftstotheslopedjoists,
whichcreatesslopedsofts.Aatsoftreducesthepotentialforentrapmentofembers
andhotgases.
Forthefascia,usenoncombustibleorre-resistantmaterials(e.g.,re-retardant-treated
lumber,ber-cementboard).
Foreavevents,followtheguidanceinFactSheet#8,Vents.
Embers andhot gases
from fire
Exterior wall
cladding
Fascia
Gutter
Rafter
Underside of
roof deck
Figure 3. An enclosed
overhangwitha
horizontalsoft.
Figure 2.Aneavewithessentiallynooverhang.
Gutter
Embers and hotgases from fire
Horizontalsoffit
Exteriorwallcladding
Fascia
Rafter
Undersideof roof deck
Soffitframing
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FS No. 6 Eaves, Overhangs, and Softs HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of3
Guidance for Existing Buildings
Installasoftunderopenoverhangsaccordingtotheguidanceprovidedabove.
Evaluatethere-resistanceofexistingsoftsandreplacesoftsthatarenotre-resistant
accordingtotheguidanceprovidedabove.Someexistingsofts(suchasthoseconstructedof
plywood)canbecoveredwithanoncombustibleorre-resistantmaterialsuchasber-cement
boardorstucco.
InveryhighFireSeverityZones,installexterior5/8-inchre-resistantgypsumboardbetween
theexistingandnewsoftmaterialsforenhancedreresistance.
Ifthefasciaiscombustible,coverthefasciaboardwithanoncombustibleorre-resistant
material(e.g.,re-retardant-treatedlumber,ber-cementboard).
Foreavevents,followtheguidanceinFactSheet#8,Vents.
Considerations
Plantingcombustiblevegetationundereavesandoverhangsshouldbeavoided(seeFact
Sheet#4,DefensibleSpace).
Effectiveness
AllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZones.
Resources
UnderEaveSFMStandard12-7A-3,2001CaliforniaReferencedStandardCodes(Part12,
Title24,C.C.R.).http://www.re.ca.gov/re_prevention/downloads/Part_12_CA_SFM_12-
7A-3_Test_Standards.pdf.
http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdf -
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FS No. 7 Exterior Walls HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of3
Exterior WallsHome Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 7
PurposeToprovideguidanceonthedesignandconstructionofexteriorwallsinwildrezones.Guidance
pertainstobothnewandexistingbuildings.
Key Issues
Exteriorwallsaresusceptibletowildre
ames,conductiveheat,andradiantheat.
Flamesandheatcanignitecombustiblewall
coverings.Whenexteriorwallsignite,the
recanspreadtoothercomponentsofthebuildingsuchastheroof,soft,windows,and
doors,resultinginsubstantialdamagetoor
totallossofthebuilding.
Windborneembersandrebrandsarealso
sourcesofignition.Emberscanbecome
trappedincracksinwalls,windowopenings,
anddoortrimboardsandignitecombustible
materials.Windbornerebrandscanignite
wallcoverings.
Thereresistanceofexteriorwallsdependsprimarilyonwhatthewallsareconstructedofandtheamountofnearbycombustiblematerial.
Sometypesofconstructionmaterialssuchasvinylsidingdonotburnbutcanmeltwhen
exposedtohightemperatures(seeFigure1),allowingtheretoreachtheunderlyingwall
componentsandpenetratetheinteriorofthebuilding.
Guidance for New Buildings
Forthebestprotection,ensurethatexteriorwallcoveringsarenoncombustibleorre-resistant
andnotsusceptibletomelting.Concrete,ber-cementpanelsorsiding,exteriorre-retardant-
treatedwoodsidingorpanels,stucco,masonry,andmetalarerecommendedmaterials.With
thesecoverings,thecoveringitselfshouldnotigniteandfuelthere.Examplesofthetypes
ofcoveringsthatarenotrecommendedarewoodsidingthatisnotre-retardant-treated,vinyl
siding,metalsidingsusceptibletowarping,andanexteriorinsulationnishsystem.
Ensurethattheentirewallassemblyhasare-resistanceratingtestedinaccordancewith
AmericanSocietyforTestingandMaterials(ASTM)E119.Althoughtheaboverecommended
typesofcoveringsprovideaninitialbarriertoames,heatmaypassthroughthecovering
Figure 1.Vinylsidingthatmeltedandwarped
duringawildre(recenter.berkeley.edu).
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Page2of3 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 7 Exterior Walls
andigniteunderlyingwallcomponents.Are-resistanceratingindicateshowlongundertest
conditionsawallassemblycanpreventamesandheatfrompassingthroughthewall.A
minimumre-resistanceratingof1hourisrecommended,buthigherratingsprovidegreater
protection.
Complywiththerequirementsofthere-ratedassembly,includingusingtheexacttypeof
materials,conguration,andattachmentusedduringthetestingthatestablishedtherating.
Forexceptionalreresistance,useinsulatedconcreteform(ICF)walls,cast-in-placeconcrete,
orfullygroutedconcretemasonryunits.IfICFisselected,useastuccoormasonrywall
coveringtoprotecttheplasticfoamforms.
Ifber-cementormetalwallcoveringsare
used,installonelayerof5/8-inchtypeX
exteriorgypsumboardwithtapedjoints
underneathhousewrap(seeFigure2).
Forber-cementsiding,thegypsumboard
providessecondaryprotectionifthesiding
decomposesandfallsawayduringare.For
metalpanels,thegypsumboardminimizes
thetransferofheatradiatedfromthemetal
panelstootherwallcomponents.
Forvinylsiding(notethatvinylsidingisnot
recommended),installonelayerof5/8-inch
typeXexteriorgypsumboardwithtaped
jointsunderneathhousewrap.Ifthevinyland
housewrapmeltduringare,theunderlyinggypsumboardwillprovidesomeprotection.
Usenoncombustibleorre-resistantmaterialsuchasexteriorre-retardant-treatedwoodor
ber-cementfortrimboardsarounddoors,windows,eaves,andcorners.
Guidance for Existing Buildings
Replaceexteriorwallcoveringsthatarecombustible,aresusceptibletomelting,orcanreadily
transmitheatwithoneoftherecommendedcoveringslistedabove.Examplesofthetypes
ofcoveringsthatneedtobereplacedarewoodsidingthatisnotre-retardant-treated,vinyl
siding,metalsiding,andanexteriorinsulationnishsystem.
Beforereplacingvinylormetalsiding,checkwhetherthereisanunderlyinggypsumboard
substrate.Ifso,remedialworkmaynotbeneeded.
Determinewhetherkeepingtheexistingcoveringandcoveringitwith5/8-inchtypeX
gypsumboardandanewcoveringisaviableoption.
Considerations
Forstudwalls,metalstudscanbeusedinlieuofwoodstuds.Metalstudsdonotignite,but
theytransferheatmorereadilythanwoodstudsandcandeformandcollapseattemperatures
thatcanoccurinawildre.Currentdataareinsufcientregardingthewildreperformanceof
Figure 2.Exampleofare-ratedwallassembly.
Exterior covering
Wall stud
Sill plate
5/8-inch type X
exterior gypsum board
Wood sheathing
Housewrap
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FS No. 7 Exterior Walls HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of3
wallsthathavewoodstudsversusmetalstuds.
Maintainingandremovingcombustibledebris(suchasvegetationandleaves)andrewood
neartheexteriorwallsregularlyreduceabuildingsvulnerabilitytoignitionduringawildre
(seeFactSheet#4,DefensibleSpace).
Effectiveness
Awallassemblywithoneoftherecommendedcoveringsandaminimum1-hourre-resistance
ratingiseffectiveinallFireSeverityZones.
Resources
ASTME119-08aStandardTestMethodsforFireTestsofBuildingConstructionandMaterials.
http://www.astm.org/Standards/E119.ht m.
MaterialsandConstructionMethodsforExteriorWildreExposure:ExteriorWallSidingand
SheathingSFMStandard12-7A-1,2001CaliforniaReferencedStandardCodes(Part12,Title24,C.C.R.).http://www.re.ca.gov/re_prevention/downloads/%20Part_12_CA_SFM_12-
7A-1_Test_Standards.pdf.
http://www.astm.org/Standards/E119.htmhttp://www.astm.org/Standards/E119.htmhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-1_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-1_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-1_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-1_Test_Standards.pdfhttp://www.astm.org/Standards/E119.htm -
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FS No. 8 Vents HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of5
VentsHome Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 8
PurposeToprovideinformationaboutwaystoavoidwindborneembers,convectiveheat,andradiantheat
enteringexteriorventopenings,whichcanleadtotheignitionofinteriorbuildingcomponentsand
contents.Guidancepertainstobothnewandexistingbuildings.
Vent Systems and Vent Openings
Ventscanbedividedintothoseforattics;ventilatedcathedralceilings;crawlspaces;andheating,
ventilation,andairconditioning(HVAC)systems.
Attic and Cathedral Ceiling Vents
Ridge vent acontinuousventinstalledalongthefulllengthoftheroofridge.Ridgevents
allowexltrationofatticair,orinventilatedcathedralceilingsorventilatednailbaseboards,the
exltrationofairfromtheventilationcavityofthecathedralceilingornailbaseboards.Ridge
ventsaremetalorplastic.Someridgeventshaveinternalbafemediatoavoidtheentranceof
wind-drivenrainandsnow.
Soft vent acontinuousorintermittentventinstalledalongasoft.Softventsprovideair
intakeintotheatticorintotheventilationcavityofcathedralceilingsandventilatednailbase
boards.Softventsaremetalorplasticand
oftenhaveascreentopreventinsectentry.
Vinylandmetalsoftsarecommonlyventedby
intermittentlyspaced,perforatedsoftpanels.
Gable-end vent aventlocatedinthegable-
endwall,justbelowtheroofridge.Gable-end
ventsallowairtoowintoandoutofattics.
Gable-endventsnormallyhavelouverblades
toavoidtheentranceofwind-drivenrain
andsnow(seeFigure1).Thistypeofventis
commonlymetalandnormallyhasaninsect
screen.
Through-roof vent aventthatpenetratesthe
rooftoallowexltrationofatticair;alsoknown
asaneyebrowordormervent.Through-roof
vents,includingsheetmetalgoose-necks,arealsoavailableforkitchenorbathroomexhaust
ducts.Through-roofventsaremetal,plastic,orrigidberglass.
Figure 1. Alouveredventopeningcanbeusedfor
gable-endventingorforconnectiontoductwork.
Horizontal louvers can
prevent embers from
entering the ventilation
system
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Page2of5 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 8 Vents
Crawlspace Vents
Crawlspace vent aventinstalledintermittentlythroughthefoundationwallseveralinches
above-grade.Crawlspaceventsallowairtoowintoandoutofthecrawlspace.
HVAC System Vents
Through-roof vent (seeabove).
Wall louvers aventopeningonanexteriorwall(seeFigure1).Walllouversareconnectedto
theHVACductworkwhereairentersorisexhaustedfromthebuilding.Louversarecommonly
metal.Thelouverbladesarenormallyinaxedposition(i.e.,cannotberotated),butsome
havemoveablebladesthatcanberotatedtoclosetheventopening.
Key Issues
Embersandhotgasescanbeblownorpulled
intoventopeningsandenteratticspaces,
crawlspaces,andductwork,leadingtoignitionoftheinteriorofthebuilding(seeFigure2).
Debriscanaccumulateatventopeningsand
igniteduringawildre.
Guidance for New Buildings
All Vents
Specifyandinstallnoncombustiblematerialforallvents.Metalproductsarerecommendedfor
ventsandventashing.
Specifyandinstallcorrosive-resistant,metalmeshscreenswithamaximumopeningof
1/4inchatallventopenings.
Specifyandinstallventopeningswithamaximumnetfreeareaof144squareinches.
Placeallventopeningsatleast10feetfromotherbuildingsorpropertylinestoavoidignition
fromembersandhotgasesfromanadjacentbuildingthathasignited.
Attics (including Cathedral Ceiling and Ventilated Nailbase Boards)
Protectingatticspacesfromwildresisachallengebecauseairisnaturallydrawnintoattics
throughventopenings.Althoughinsectscreenscanpreventtheentryofmanyembers,vent
screensandlouversdonotpreventtheentryofhotgases.Ventsthatallowairtoowintoandout
undernormalconditionsandalsoavoidtheentryofembersandhotgasesinawildrecanbe
providedinthefollowingways:
Gable-end vent .Insteadofusingridgevents,specifyandinstallgable-endventswithspecially
designedmetalshutters.Whenawildrethreatens,theshutterscanbeplacedoverthegable-
endvent.Ahingedshutterthatcanbelatchedinanopenorclosedpositionisrecommended
(seeFigure3).Adetachableshutterdesigncanbeused,butwhentheshuttersareneeded,
Figure 2. Embersorhotgasescanbeblownor
pulledintovents.
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FS No. 8 Vents HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of5
thehomeownermustrememberquickly
wheretheyarestored.Shuttersshouldhave
agasketthatprovidesatightsealbetween
theshutterandgable-endvent.Foramore
conservativeshutter,ashutterwithan
insulatedcoreencapsulatedbymetal(similartoarefrigeratordoor)canbeused.
Whengable-endventsarecombinedwith
softvents,effectiveatticventilationcan
beachievedwhentheatticspaceissimple
andrelativelysmall,suchasasmall,gable-
roofedhouse.Ifthehousehasacomplexroof
areaortheatticistoolargetobeeffectively
ventilatedbygable-endvents,ridgeventsor
through-roofventsshouldbeused.
Ridge vent .Continuousridgeventscanprovideeffectiveventilation,buttypicalridge
ventsarenothighlyre-resistant.Althoughairisnormallyexhaustedthroughridgevents,
hotgasescanentertheridgeventandowintotheattic.Emberscanalsoenterthroughthe
ridgeventiftheventdoesnothaveinternalbafemedia.Typicalridgeventsarethereforenot
recommendedunlesstheatticcongurationorsizerequiresridgeventstoventilatetheattic
effectively.Ifridgeventsareused,metalventswithinternalbafemediaarerecommended,
butduringawildre,theinternalbafe
materialmaymeltandbecomeineffective in
atpreventingembersfromentering.
Soft vent . Aswithridgevents,typicalsoftventsarenothighlyre-resistant,but
becausetheyareanecessaryelementofa
ventedattic,theycannotbeeliminated.To
avoidembersandhotgasesfromentering
thevents,speciallydesignedmetalshutters
overthesoftventopeningsshouldbe
speciedandinstalled.Seetheshutter
recommendationsforgable-endventsabove.
Through-roof vent . Through-roofventsarenot
recommendedforatticventilationbecausethereisnoknowneffectivestrategyfor
avoidingembersandhotgasesfromentering,
otherthanblockingthevent.A1/4--inch
screeniseffectiveatkeepingoutrebrands
andembersthatarelargerthan1/4-inchbut
willnotkeepoutsmallerembersorhotair.
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 Attic
Themostconservativeapproachto
preventingembersandhotgasesfrom
enteringtheatticistoeliminateattic
ventilation,butunventilatedatticsare
controversial.Althoughallowedbythe
InternationalResidentialCode,provided
theCodescriteriaaremet,unventilated
atticsmaynotcomplywithlocalbuilding
codes.
However,whenunventilatedatticsare
allowedbythebuildingcodeorcode
complianceisnotanissue,andwhenclimaticandinteriorhumidityconditions
(e.g.,noindoorswimmingpools)are
conducivetoanunventilateddesign,
anunventilatedatticisareliableway
topreventembersandhotgasesfrom
enteringtheattic.
Figure 3.Ahingedshutter.
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Page4of5 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 8 Vents
Becauseofvariablereliabilityofblockingtechniquesandthepotentialdangerofhomeowners
fallingfromroofswhileattemptingtoblockvents,blockingisnotrecommended.
Crawlspace Vents
Specifyandinstallspeciallydesignedmetalshuttersovercrawlspaceventopenings.A1/4-inch
meshscreenshouldalsobeinstalledovertheventopening.Seetheshutterrecommendations
forgable-endventsabove.
HVAC System Vents
Wall louvers . Specifyandinstallspeciallydesignedmetalshuttersoverwalllouvers(seethe
shutterrecommendationsforgable-endventsabove)orspecifyandinstallwalllouversthat
haveadjustabletight-ttingbladesthatcanbeclosedwhenawildrethreatens.
Asanadditionalconservativemeasurewitheithershuttersoradjustableblades,specifyand
installredamperswithintheductsimmediatelybehindthewalllouvers.Ifsufcientlyhigh
heatpenetratesbeyondthelouver,theredamperwillautomaticallycloseandpreventhighheatfrompenetratingfarther.
Through-roof vents .Asdiscussedinatticventilation,through-roofventsarenotrecommended.
Ratherthanrunningductworkthroughtheroof,extendtheductworktoanexteriorwallwhere
itcanbettedwithawalllouverandshutter.Ifitisnecessarytopenetratetheroof,however,
installaredamperintheductattheplaneoftheroofassembly.
Guidance for Existing Buildings
Ifthehomehasridgeventsorwalllouversandtheyarenotmetal,replacethemwithmetal
ventsaccordingtotheguidanceprovidedabove.
Ifexistingventopeningsdonothavescreensorifthescreenopeningsarelargerthan
1/4-inch,installmetalscreensaccordingtotheguidanceprovidedabove.
Installshuttersovergable-endvents,softvents,crawlspacevents,andwalllouvers.Ifthe
existingwallorsoftiscombustible,shuttersmaynotbeeffective.Inthiscase,installing
shuttersisprobablycost-effectiveonlyifdoneinconjunctionwithupgradestothewallorsoft.
Considerations
Low-prole,through-roofventshavebeenusedinplaceofsoft/eaveventswithgreatsuccess,
butnoneoftheseproductshavebeentestedatthetimeofthispublication.
Thehomeownershouldperiodicallyhaveaprofessionalremovedebristhathasaccumulated
nearoronventopenings,ventscreens,andlouverblades.
Theamountofvegetationnearventopeningsshouldbelimited(seeFactSheet#4,Defensible
Space).
Tominimizethepossibilitythatembersandhotgaswillbepulledintothehome,theHVAC
system,includingexhaustfans,shouldbeturnedoffwhenawildrethreatens.Atticexhaust
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FS No. 8 Vents HomeBuildersGuidetoConstructioninWildreZones 09/08 Page5of5
fansshouldalsobeshutdown.Atticexhaustfansthatarecontrolledbyathermostatmayneed
tobedeactivatedbytrippingthecircuitbreaker.
Forsoftconstruction,seeFactSheet#6,Eaves,Overhangs,andSofts.
Effectiveness
AllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZonesexceptas
notedbelow.
Ifaridgeventisinstalled,theventopeningmaybebreachedduringextremereexposureby
embersorhotgases,whichcouldresultinignitionoftheattic.
Theeffectivenessofshutter-protectedventopeningsisdependentonthedeploymentofthe
shuttersbythehomeownerpriortoreexposure.
Resources
Slack,P.2000.Firewise Construction Design and Materials.ColoradoStateForestService.
UnderEaveSFMStandard12-7A-3,2001CaliforniaReferencedStandardCodes(Part12,Title
24,C.C.R.).Availableatwww.re.ca.gov/re_prevention/downloads/Part_12_CA_SFM_12-
7A-3_Test_Standards.pdf.
http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-3_Test_Standards.pdf -
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FS No. 9 Gutters and Downspouts HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of2
Gutters andDownspouts
Home Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 9
Purpose
Toprovideguidanceaboutinstallingre-resistantguttersanddownspoutstoreducethepotential
fordamagetohomesandotherbuildingsfromwildres.Guidancepertainstobothnewand
existingbuildings.
Key Issues
Debrissuchasbranches,leaves,andpineneedlescan
becometrappedingutters(seeFigure1).Thedebris
canbeignitedbyyingembersorrebrandsduringa
wildre,andtherecanspreadtotheroof.
Guttersanddownspoutsareoftenconstructedof
plastic.Plasticcanmeltwhenexposedtothehigh
temperaturesthatcanoccurduringawildre.
Guidance
Installnoncombustibleleafguardsoverguttersto
preventtheaccumulationofcombustibledebris.Types
ofleafguardsincludemetal-meshscreensandmetal
hoodsthattintothegutter(seeFigure2).
Useguttersanddownspoutsconstructedof
noncombustiblematerialssuchasgalvanizedsteel,
copper,andaluminum.Metalhoodleafguardsare
recommendedbecausetheydonotmeltandare
relativelyeffectiveinkeepingdebrisoutofgutters(see
Figure2).
ConsiderationsIntenseheatfromawildrecandistortnoncombustible
gutters,leafguards,anddownspouts,andtheymayneed
tobereplacedafterawildre.
Someleafguardscanbecomedislodgedovertime,reducingtheireffectiveness.
Figure 2.Leafguardsallowrainwaterintothegutterbutkeepcombustible
debrisout.
Leaf guard
Figure 1. Debrisingutterscanignite
andleadtoignitionoftherooforfascia
board.
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Page2of2 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 9 Gutters and Downspouts
Sometypesofleafguardsdonotpreventalltypesofdebrisfromaccumulatinginthegutter.
Forexample,mesh-typeleafguardsallowpineneedlestoaccumulate.Leafguardsandgutters
shouldthereforebecheckedregularlyanddebrisremovedifnecessary.
Effectiveness
Noncombustiblegutters,leafguards,anddownspoutsareeffectiveinallFireSeverityZones.
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FS No. 10 Windows and Skylights HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of4
Windows andSkylights
Home Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 10
Purpose
Toprovideinformationaboutmeasuresthatcanbetakentoavoidtheignitionofinteriorbuilding
componentsandcontentsduetotheintrusionofwindborneembers,hotgases,andradiantheat
throughwindows,slidingglassdoors,doorvisionpanels,andskylights.Guidancepertainstoboth
newandexistingbuildings.
Key Issues
Glazinginhomesistypicallyvulnerabletowildre
(seeFigure1).(Glazingreferstotheglass,
plastic,orberglass-reinforcedtranslucent
materialinwindows,slidingglassdoors,door
visionpanels,andskylights.)Failedglazingallows
easypassageofembers,hotgases,andradiant
heatintotheinteriorofthebuilding.Glazingis
vulnerabletowildreintwoways:
Flameimpingementandradiantheatcanbe
severeenoughtomeltorbreakmanytypes
ofglazing.Asinglepaneoftypicalresidential
glasscanfailwithin5minutesofexposuretoa
wildre(Slack,2000).
Windbornerebrandscanhavesufcient
momentumtobreakmanytypesofglazing.
Theframesforwindows,slidingglassdoors,and
skylightsareconstructedofmetal,plastic,wood,
oracombinationofthesematerials.Plasticand
woodenframesaresusceptibletofailurefrom
burningormelting(seeFigure2).Iftheframeor
sashfails,theentireglazingmayfallout.
Guidance on New Buildings
Thissectionprovidesguidanceonglazing,frames,
re-ratedassemblies,andexteriorwindowshutters.
Figure 1.Potentialdamagetoawindow
duringawildre.
Embers melt vinyl framesand ignite wooden frames
Radiant heat and windbornefirebrands can shatter windows
and lead to interior damage
Figure 2.Combustibleframing(recenter.
berkeley.edu).
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Page2of4 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 10 Windows and Skylights
Glazing
Avarietyofproductsareavailableforglazinginwindows,slidingglassdoors,doorvisionpanels,
andskylights.Glazingcanbeinasingle-ormulti-panedconguration.Therecommendedglazing
productsforhomesinwildrezonesarelaminatedglass,temperedglass,glasswithalow-
emissivity,berglass-reinforcedtranslucentglazing,andinsulatedglazingunits(IGUs).Glazing
productsthatarenotrecommendedareannealedglass,ceramicglass,andplasticglazing.
Recommended
Laminated glass . Laminatedglassprovidesresistancetowindbornerebrands.Ifa
rebrandstrikeswithenoughmomentumtobreaktheglass,theplasticlminthecoreof
theglasswillkeeptheglazingintheframe,allowingthebrokenglasstocontinuetoresist
rebrandimpacts,embers,andhotgases.Iftheplasticlminthecoregetssufcientlyhot,
thepanewilldelaminatewhetherornottheglasshasbeenbroken.Iflaminatedglassis
specied,itshouldeitherbeprotectedbyshutters,asdiscussedbelow,orcombinedwith
temperedglassinanIGU.SeetheinformationonIGUsbelow.
Tempered glass .Temperedglassismoreresistanttoheatandamesthanlaminatedglassorannealedglass(seebelow).Theresistanceoftemperedglasscanbeenhanced
withalow-ecoatingoraproprietaryreectivecoating,asdiscussedbelow.Firebrands
withsufcientmomentumcanbreaktemperedglass.Toavoidbreakage,theglasscanbe
protectedbyshutters,asdiscussedbelow.Anotheralternativeistospecifyandinstallan
IGUwithalaminatedglassinnerpane.
Low-emissivity (low-e) coating . Glasswithalow-ecoatingprovidesahigherlevelof
resistancetoradiantheatthanothertypesofglazingbecausethecoatingreectsradiant
heat,reducingtheprobabilitythattheheatwillbeabletoenterthebuilding.Thecoating
shouldbeontheinnersurfaceoftheexteriorpane.
Proprietary berglass-reinforced translucent glazing .Thisproductisavailableforskylights
andwalls.TheskylightmaterialhasaClassArating.SeeFactSheet#5,Roofs,fora
discussionofthistypeofrating.
Insulated glazing unit. AnIGUconsistsoftwo
orthreepanesofglassthatareseparatedbya
sealedairspace.Double-panedannealedunits
lastabout10minutesinawildre,twiceas
longassingle-panedwindows.Inmanycases,
10minutesislongenoughtoprovideprotection
fromthere.Iftherstpanefails,thesecond
panemuststillbepenetrated(Slack,2000)
(seeFigure3).Laminatedglass,tempered
glass,andglasswithalow-ecoatingcanbe
combinedinvariouswaysintoanIGU.
Two panes of glass with
a layer of air between
The first pane may shatter
within 5 minutes of the
onset of a wildfire
The second pane offers
5 minutes of additional
protection
Figure 3. Double-panedglazing.
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FS No. 10 Windows and Skylights HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of4
NotRecommended
Annealed glass .Annealedglass(alsoknownascommonoatglass)iscommonlyusedin
residentialwindows.Annealedglassisthemostsusceptibletowildresofthevariousglass
typesandisnotrecommendedforhomesinwildrezonesunlessprotectedbyshutters,as
discussedbelow.
Ceramic glass. Thisspecialtyglassiseffectiveatresistingames,butittransmitsradiant
heatreadily.Ifceramicglassisusedforexteriorglazing,heatthatishighenoughto
causeignitioncanbetransmittedintotheinteriorofthebuilding.Ceramicglassisnot
recommendedforhomesinwildrezones.
Plastic glazing. Acrylicandpolycarbonateareoftenusedinskylightsandsometimesin
windows.Becauseplasticglazingcanmeltduringawildre,itisnotrecommendedfor
homesinwildrezones.
Frames
Avarietyofproductsareavailableforwindowandskylightframes.Toavoidwindowfailure,frames
shouldbeconstructedonlyofmetalormetal-cladwood.Woodenandplasticframesshouldnot
beused.
Fire-rated Assemblies
Ifare-ratedwallisspecied,windowsandslidingglassdoorsthatarecommensuratewiththe
wallintermsofthereratingarerecommended.Forexample,awindowwitha1-hourratingis
intendedtobeusedinawallwitha2-hourrating,andadoorwitha3/4-hourratingisintended
tobeusedinawallwitha1-hourrating.However,awindowwithahigherreratingmaybeused.
SeeFactSheet#7,ExteriorWalls,forinformationaboutre-ratedwalls.
Ifare-ratedwallisnotspecied,anIGUwithametalormetal-cladwoodenframeshouldbeused.SeetheinformationonIGUsabove.
Exterior Window Shutters
Exteriorwindowshutterscanprovideprotectionfor
windowsandslidingglassdoorsinawildre.Solid
metalshuttersareunlikelytoigniteormeltandare
thereforerecommendedoverwoodenorplasticshutters
(seeFigure4).Forenhancedprotection,aninsulated
metalshuttercanbedesignedandfabricated.Ifthe
buildingislocatedinawindbornedebrisregionwithinahurricane-proneregion,theshuttershouldmeetthe
windbornedebriscriteriaintheAmericanSocietyof
CivilEngineersstandard,ASCE7-05(2006).Figure 4. Thismetalshutterhastop
andbottomtracksthatarepermanently
anchoredtothewall(FEMA577).
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Page4of4 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 10 Windows and Skylights
Guidance on Existing Buildings
Windowsandslidingglassdoors,includingframes,thataresusceptibletodamagefrom
awildreshouldbereplacedwiththecomponentsthatarerecommendedaboveand/or
protectedbyshutters,asrecommendedabove.
Doorvisionpanelsthataresusceptibletodamagefromawildreshouldbereplacedwith
temperedglasswithalow-eorproprietaryreectivecoating,providedthedoorhassufcient
reresistance(seeFactSheet#11,ExteriorDoors).
Skylightswithplasticglazingshouldbereplacedwithoneoftherecommendedtypesof
glazing,asdescribedabove.
Considerations
Shuttersprotectthehomenotonlyfromwildresbutalsofromextremeweather.
Double-panedglassismoreenergyefcientthansingle-panedglass.
Aproprietaryreectivecoatingisavailableforapplicationtotemperedglass.Thecoatingacts
likealow-ecoatinginthatitreectsradiantheat,buttheproprietaryreectivecoatingmaybe
moreeffective.Formoreinformationonthisproductandacomparisonofreratingsofvarious
typesofglassproductsandsizes,seewww.safti.com.
Effectiveness
Windowassemblieswith3/4-hourminimumratingsareeffectiveinallFireSeverityZones.
Metalcladdingonmetalclad-woodframesmaybecomedistortedduringwildreexposureand
requirereplacement.
Temporaryshuttersareeffectiveonlyifthehomeownerhassufcienttimetoputtheshutters
intoplace.
Resources
AmericanSocietyofCivilEngineers.(2006).Minimum Design Loads for Buildings and Other
Structures.ASCE7-05.
CenterforFireResearchandOutreach.UniversityofCalifornia,Berkeley:CollegeofNatural
Resources.http://recenter.berkeley.edu/default.htm.
ExteriorWindowsSFMStandard12-7A-2,2001CaliforniaReferencedStandardCodes(Part12,
Title24,C.C.R.).http://www.re.ca.gov/re_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.
http://www.safti.com/http://www.safti.com/http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-2_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-2_Test_Standards.pdfhttp://www.fema.gov/library/viewRecord.do?id=2739http://www.safti.com/http://www.safti.com/http://www.safti.com/http://www.fema.gov/library/viewRecord.do?id=2739http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-2_Test_Standards.pdfhttp://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-7A-2_Test_Standards.pdfhttp://www.safti.com/ -
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FS No. 11 Exterior Doors HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of3
Exterior DoorsHome Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 11
PurposeToprovidebasicguidanceonthedesignandconstructionofexteriordoors,includinggarage
doors,onbuildingsinwildrezones.Guidancepertainstobothnewandexistingbuildings.
Key Issues
Exteriordoorsaresubjecttothesame
typesofexposureasexteriorwallsina
wildre(seeFigure1).However,exterior
doorsaretypicallymuchthinnerandless
re-resistantthanexteriorwallsandcanthereforeburnthroughmuchfaster.
Flamesandhotgasescanignite
combustiblematerialsinadooranddoor
frame.
Flamesandhotgasescanpenetrate
openingsbetweenthedoorandframeand
betweenthedoorandthreshold(oroorif
nothresholdexists).
Emberscanbecomelodgedinopenings
betweenthedoorandframeandbetween
thedoorandthreshold(oroorifno
thresholdexists).Emberscanalsobe
blownthroughtheopeningsintothe
interiorofthebuilding.
Flames,convectiveorradiantheat,and
airbornerebrandscanbreakglassina
door.
Exterior Door Characteristicsand Ratings
Typesofexteriordoorsincludesolidentrancedoors,entrancedoorswithglassvisionpanels,
slidingglassdoors,stormdoors,screendoors,garagedoors,andcellardoors.
Solidexteriordoorsaretypicallymadeofwoodormetal.Doorswithasolid,noncombustible
mineralcoreareclassiedasre-rateddoorsandareratedbyUnderwritersLaboratories
(UL)accordingtothelengthoftimetheycanresistre(ULStandard10C)(UL,1998).UL
Figure 1. Typesofexposurethatexteriordoorscanbe
subjecttoinawildre.
Welcom
e
Welcom
e
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
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Page2of3 09/08 HomeBuildersGuidetoConstructioninWildreZones FS No. 11 Exterior Doors
classicationsforinteriorandexteriorre-rateddoorsandtheirframesrangefrom3-hourto
20-minuteratings.Exteriorre-rateddoorsareavailablewitharatingof1houror3/4hour.
Thereratingfordoorsisintendedtoequalthree-fourthsofthereratingofthesurroundingwall.
Forexample,adoorwitha1-hourratingisintendedtobeusedinawallwith2-hourrating,and
adoorwitha3/4-hourratingisintendedtobeusedinawallwitha1-hourrating.However,adoor
withahigherreratingmaybeused.
Guidance for New Buildings
Ifare-ratedexteriorwallisspecied(seeFactSheet#7,ExteriorWalls),specifyandinstalla
re-rateddoorandframe.Asexplainedabove,theratingofthedoorandframeshouldbeat
leastthree-fourthsoftheratingofthewall.Inaddition,specifyandinstallre-ratedhardware.
FollowtheguidancepertainingtodoorglassvisionpanelsandglassslidingdoorsinFact
Sheet#10,WindowsandSkylights.
Toavoidembersandhotgasespenetratingtheinteriorofthebuildingbetweenthedoor
andthedoorframe,installadjustableweatherstrippingontheinteriorsideofthedoor
frameandspecifyandinstallanautomaticdoorbottomorthresholdweatherstripping.The
weatherstrippinganddoorbottomshouldbetestedinaccordancewithULStandard10C.
Weatherstrippingisrelativelyinexpensive(seeFigure2).
Garagedoorsaretypicallymadeofwood,aluminum,orsteel
andareinsulatedornon-insulated.Unlikestandardegress/
ingressdoors,garagedoorsarenotnormallytestedforre
resistance(seeFigure3).Toprotectthegaragedoorand
entirebuilding,followtheguidancelistedbelow.
Specifyandinstallinsulated,metalgaragedoors.
Toavoidembersandhotgasespenetratingthegarage,
specifyandinstallweatherstrippingthathasbeentested
inaccordancewithULStandard10Caroundtheentire
garagedoor.
Figure 2.Exampleofadjustable
weatherstripping(FEMA577).
Fire-resistant
weatherstripping
Noncombustible or
fire-resistant trim
Insulated metal door
Figure 3.Agaragedoorwith
noncombustibleandre-resistant
components.
Door
Adjustable
jamb
weatherstrip
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FS No. 11 Exterior Doors HomeBuildersGuidetoConstructioninWildreZones 09/08 Page3of3
Forexteriortrimthatcoverstheopeningbetweenthedoorframeandexteriorwall,specifyand
installnoncombustibleorre-resistantmaterialsuchasre-retardant-treatedwoodorber-
cementboard.
Guidance for Existing Buildings
Addweatherstrippingtodoors,asdescribedabove.
Replacevisionpanelsindoors,ifnecessary,asdescribedinFactSheet#10,Windowsand
Skylights.
Replaceslidingglassdoorsand/orprotectwithshutters,asdescribedinFactSheet#10,
WindowsandSkylights.
Replacewoodengaragedoors,particularlyiftheydonothaveasolidcore.
Replacewoodenegress/ingressdoorswithoutasolidcore,althoughegress/ingressdoorsare
oftenrelativelyre-resistantcomparedtoothercomponentsofthebuildingandthereforenot
normallyahighpriorityforremediation.
Considerations
Metalandmetal-claddoorframescantransmitheatduringare,andtheheatcanignitethe
surroundingexteriorwallifthewallisnotconstructedtore-resistantstandards,asnotedabove.
Formoreinformation,seeFactSheet#7,ExteriorWalls.
Effectiveness
AllmitigationmeasureslistedinthisFactSheetareeffectiveinallFireSeverityZonesexceptas
follows:
GaragedoorsarenotnormallytestedforreresistanceandmaynotprovideeffectivereresistanceinhighFireSeverityZones.
Underveryhighheatorprolongedexposuretoheat,weatherstrippingmaterialcanmeltor
burn,loweringitseffectivenessinpreventingembersandhotgasesfromenteringtheinterior
ofabuilding.
Resources
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.
SteelDoorInstitute(SDI).2001. Basic Fire Door Requirements. TechnicalDataSeriesSDI
118-01.http://www.steeldoor.org/res/118.pdf).
UnderwritersLaboratory(UL).1998.ULStandard10C,PositivePressureFireTestsofDoor
Assemblies.
http://www.steeldoor.org/res/118.pdfhttp://www.steeldoor.org/res/118.pdf -
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FS No. 12 Foundations HomeBuildersGuidetoConstructioninWildreZones 09/08 Page1of4
FoundationsHome Builders Guide to Construction in Wildfre Zones Technical Fact Sheet No. 12
PurposeToprovideguidanceonavoidingtheignitionoffoundationsbywindborneembersandconvective
andradiantheatinwildrezones.Guidancepertainstobothnewandexistingbuildings.
Foundation Designs
Foundationscanbeopenorclosed.Homesnormallyhaveonlyonetypeoffoundation,butsome
haveboth.
Closed Foundation
Inaclosedfoundation,thefoundationwall
extendsfromthefootingtotherstooraround
theperimeterofthebuilding.Thefoundation
wallistypicallyabearingwall.Thebelow-grade
portionistypicallycon