Local Officials Guide 

for Coastal Construction

Design Considerations, Regulatory Guidance, and 

Best Practices for Coastal Communities

FEMA P-762 / February 2009

FEDERAL EMERGENCY MANAGEMENT AGENCY

Local Officials Guide

for Coastal Construction

Cover Photo: Courtesy of Jennifer Smits/FEMA

i

Design Considerations, Regulatory Guidance, and 

Best Practices for Coastal Communities

FEMA P-762 / February 2009
LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

Anyopinions,findings,conclusions,orrecommendationsexpressedinthispublicationdonotnecessarily

reflecttheviewsofFEMA.Additionally,neitherFEMAnoranyofitsemployeesmakesanywarrantee,

expressedorimplied,orassumesanylegalliabilityorresponsibilityfortheaccuracy,completeness,or

usefulnessofanyinformation,product,orprocessincludedinthispublication.Usersofinformationfrom

thispublicationassumeallliabilityarisingfromsuchuse.

ii
FEDERAL EMERGENCY MANAGEMENT AGENCY

Acknowledgements

The preparation of this document was sponsored by the FEMA Mitigation Directorate. It has been 

developed based on the work of several recent publications, new insights from recent hurricanes, the 

post-disaster assessment findings of FEMA Mitigation Assessment Teams, and other sources of 

information on residential coastal construction. The principal contributing authors of the supporting 

reference documents are gratefully acknowledged. 

For this manual, the following individuals are acknowledged:

Primary Authors:

Scott Tezak, URS Corporation – Project Manager

David K. Low, DK Low & Associates, LLC

Adam Reeder, PBS&J

Contributors:

Chris Hudson – FEMA Headquarters – Project Monitor

John Ingargiola – FEMA Headquarters

Jacob Anderson – FEMA Headquarters

Marcus Barnes – FEMA Headquarters

Ken Wallace – FEMA Region III

Mark Vieira – FEMA Region IV

John Plisich – FEMA Region IV

Chuck Gregg – FEMA Region VI

Jeffrey Lusky – FEMA Region IX

Byron Hilado – PBS&J

Mike J. Robinson – PBS&J

Rebecca Quinn – RCQuinn Consulting

Wanda Edwards – Institute for Business and Home Safety (IBHS)

William Coulbourne – Applied Technology Council 

Chris Jones – Christopher P. Jones

iii
LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

Project Review Committee

The authors and editors gratefully acknowledge the invaluable assistance and advice provided by the 

following reviewers:

Jhun De La Cruz – FEMA Headquarters

Lois Forster – FEMA Headquarters

Tim Tolbert – City of Santa Rosa, Florida

Joe Lamb – City of Port Aransas, Texas

William York – W.H. York Consulting

Timothy Reinhold – Institute for Business and Home Safety (IBHS)

Randy Noelle – Builder

Stuart McDonald –Mercedes Homes

Mike Rimoldi – FLASH

David Conover – International Code Council (ICC)

Steve Van Note – International Code Council (ICC)

Phil Line – American Forest & Paper Association (AF&PA)

Kenneth Ford – National Association of Home Builders (NAHB)

Dana Bres – U.S. Department of Housing and Urban Development (HUD/PATH) 

Steve Mitchell – City of Pascagoula, Mississippi

Don Burrell – City of Beaumont, Texas

Lalo Flores – Missouri City, Texas

Edward Beasley – City of Portland, Texas

Robert Daehn – City of Kingsville, Texas

San Nelson – Texas Department of Insurance

Robert Smalley – City of Chesapeake, Virginia

iv
FEMA P-762

Catalog No. 09064-1

FEMA

U. S. DEPARTMENT OF

HOMELAND SECURITY

FEDERAL EMERGENCY MANAGEMENT AGENCY TOC-1

TABLE OF CONTENTS TOC

Contents

1 Introduction

1.1 Objectives ....................................................................................................................................1-1

1.2 TargetAudience ..........................................................................................................................1-1

1.3 Scope............................................................................................................................................1-1

1.4 UsingtheGuide...........................................................................................................................1-2

1.5 CoastalConstructionversusInlandConstruction ......................................................................1-4

1.6 BuildingCodes.............................................................................................................................1-5

2 Coastal Hazards and Considerations

2.1 FloodHazards:GeneralDesignConsiderations......................................................................... 2-1

2.2 WindHazards:GeneralDesignConsiderations ....................................................................... 2-19

2.3 OtherHazards...........................................................................................................................2-32

3 Investigating Regulatory Requirements

3.1 FloodplainManagementRequirementsandBuildingCodes.....................................................3-1

3.2 BuildingCodesandStandards..................................................................................................3-11

3.3 CoastalBarrierResourcesActof 1982.....................................................................................3-18

3.4 CoastalZoneManagementRegulations...................................................................................3-19

3.5 Useof theNationalFloodInsuranceProgramandCodeCrosswalk ......................................3-20

4 Permits and Inspections

4.1 Introduction.................................................................................................................................4-1

4.2 CoastalBuildingOfficial/FloodplainAdministratorsResponsibilities......................................4-2

4.3 Freeboard.....................................................................................................................................4-5

4.4 ThePre-developmentConference/Pre-applicationMeeting .....................................................4-6

4.5 CoastalConstructionPermitApplicationSteps..........................................................................4-8

4.6 PermitPlanSubmittalRequirements..........................................................................................4-8

4.7 ElevationCertificates.................................................................................................................4-10

4.8 Inspections.................................................................................................................................4-11

4.9 EnforcementandViolations......................................................................................................4-14

4.10 VarianceProcess........................................................................................................................4-15

4.11 SupplementalInformation .......................................................................................................4-16

5 Coastal Construction and Continuous Load Paths

5.1 ContinuousLoadPath.................................................................................................................5-1

5.2 Typesof LoadPaths....................................................................................................................5-4

5.3 IdentifyingLoadPathsinBuildings ............................................................................................5-5

5.4 BuildingCodesandStandards....................................................................................................5-7

5.5 ContinuousLoadPathsandBuildingSuccess ............................................................................5-8
TOC-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

TOC TABLE OF CONTENTS

6 Coastal Foundations and Best Practices

6.1 Introduction.................................................................................................................................6-1

6.2 BuildingCodesandCoastalFoundations ...................................................................................6-2

6.3 FoundationsinCoastalAreas......................................................................................................6-2

6.4 ElevatingBuildingsinCoastalAreas...........................................................................................6-5

6.5 SoilsInvestigation ......................................................................................................................6-24

7 Building Framing Systems and Best Practices

7.1 Introduction.................................................................................................................................7-1

7.2 DiaphragmsandShearWalls......................................................................................................7-2

7.3 Roof Construction.......................................................................................................................7-4

7.4 WallConstruction........................................................................................................................7-8

7.5 FloorConstruction .................................................................................................................... 7-18

8 Roof Coverings and Best Practices

8.1 Introduction.................................................................................................................................8-1

8.2 Roof Coverings:GeneralCodeRequirements ...........................................................................8-3

8.3 Re-roofingCodeRequirementsandBestPractices ..................................................................8-12

9 Exterior Cladding Components and Best Practices

9.1 Introduction.................................................................................................................................9-1

9.2 ExteriorWallCoveringsandCladdings......................................................................................9-1

9.3 ExteriorCoveringandBestPractices..........................................................................................9-6

9.4 ExteriorFloorCoverings...........................................................................................................9-11

9.5 Soffits .........................................................................................................................................9-12

9.6 ConcreteandMasonryWalls....................................................................................................9-12

10 Windows and Doors

10.1 Introduction...............................................................................................................................10-1

10.2 WindowandDoorFailure.........................................................................................................10-1

10.3 WindborneDebrisProtectionSystems......................................................................................10-4

10.4 ProtectionRequirementsforWindborneDebris ......................................................................10-6

10.5 WindowandDoorLeakage ....................................................................................................10-11

10.6 WindowandDoorAssemblyCapacities.................................................................................10-12

10.7 GarageDoors ..........................................................................................................................10-14

10.8 AdditionalResources...............................................................................................................10-16

Figures

2-1 Floodplainalonganopencoast...................................................................................................2-2

2-2 LongBeach,Mississippi:Aerialphotoof apartmentcomplex ...................................................2-3

2-3 Gulf Shores,WestBeach,Alabama:Aerialoverview.................................................................2-4
FEDERAL EMERGENCY MANAGEMENT AGENCY TOC-3

TABLE OF CONTENTS TOC

2-4Gulf Shores,WestBeach,Alabama:Insufficientpileembedment ............................................2-4

2-5OrangeBeach,Alabama:Collapseof five-story,multi-familybuilding .....................................2-5

2-6 OrangeBeach,Alabama:Collapseof five-story,multi-familybuilding .....................................2-5

2-7 Hydrostaticloadsonbuildings....................................................................................................2-6

2-8 Hydrodynamicloadsonabuildingorbuildingelement ............................................................2-7

2-9 Gulfport,Mississippi:Floodbornedebris....................................................................................2-8

2-10 Exampleof surge,wave,anddebrisdamage..............................................................................2-9

2-11 Exampleof surge,wave,anddebrisdamage..............................................................................2-9

2-12 BigLagoon,Alabama:Buildingsconstructedonpiles ...............................................................2-9

2-13 OrangeBeach,Alabama:Significanterosioncausedaparkingslabtofail ............................. 2-11

2-14 Gulf Shores,Alabama:Houseonpilefoundation.................................................................... 2-11

2-15 Gulf Shores,Alabama:Houseonpilefoundation.................................................................... 2-11

2-16 Coastalwaveheightandstillwaterdepth.................................................................................. 2-12

2-17 Floodprobabilitychart.............................................................................................................. 2-14

2-18 Exampleof aDigitalFloodInsuranceRateMap(DFIRM).................................................... 2-17

2-19 Coastalfloodhazardareas........................................................................................................ 2-17

2-20 Hurricane-proneregionsandspecialwindregions ..................................................................2-21

2-21 Wind-inducedpressuresonabuilding......................................................................................2-23

2-22 Windpressureasafunctionof windspeed...............................................................................2-25

2-23 Internalpressureconditionwhenthedominantopeningisinthewindwardwall ..................2-28

2-24 Internalpressureconditionwhenthedominantopeningisintheleewardwall ......................2-29

2-25 OceanSprings,Mississippi:Apartmentcomplexseverelydamagedbywind..........................2-31

2-26 Gulf Shores,Alabama:Partitionwallsdestroyedbyinteriorpressurization ............................2-31

2-27 NewOrleans,Louisiana:Neighborhoodwithhomesandvehiclesflooded.............................2-33

3-1 MinimumNFIPVZoneRequirements......................................................................................3-6

3-2 MinimumNFIPAZoneRequirements......................................................................................3-8

3-3 RecommendedElevationforBuildingsinCoastalAZonesandVZones............................... 3-10

3-4 Thehurricane-proneregionsalongthecoastlineof theUnitedStates.................................... 3-17

4-1 PermittingandConstructionProcessOverview.........................................................................4-9

5-1 DadeCounty,Florida,HurricaneAndrew(1992):Loadpathfailureatendgable ...................5-2

5-2 NorthCarolina,HurricaneFran(1996):Loadpathfailureinafoundation ..............................5-2
TOC-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

TOC TABLE OF CONTENTS

5-3 PuntaGorda,Florida:Roof framingdamageandlossduetoloadpathfailure ....................... 5-3

5-4 PuntaGorda,Florida:Loadpathfailureinconnectionsforaroof system ............................... 5-3

5-5 PassChristian,Mississippi:Newerhomedamagedfrominternalpressurization...................... 5-4

5-6 Loadsappliedtotheexteriorwallsof abuilding ....................................................................... 5-5

5-7 TechnicalFactSheetNo.10,Page1 .......................................................................................... 5-6

5-8 TechnicalFactSheetNo.10,Page2 .......................................................................................... 5-7

5-9 BigLagoon,Florida:Elevatedbuilding,constructedtonewercode.......................................... 5-9

5-10 BigLagoon,Florida:Thishousewaselevatedonpiles.............................................................. 5-9

5-11 BigLagoon,Florida:Thishousewaselevatedonpiles.............................................................. 5-9

6-1 Recommendedopen-foundationpracticeforbuildingsintheCoastalAZoneandVZone .... 6-4

6-2 NavarreBeach,Florida:Slab-on-gradefoundationfailureduetoerosion................................ 6-4

6-3 NavarreBeach,Florida:Close-upof foundationfailureshowninFigure6-2........................... 6-5

6-4 PlaqueminesParish,Louisiana:Homethathadbeenelevatedonfill ....................................... 6-6

6-5 Buildingfailurecausedbyunderminingof crawlspacefoundationduringHurricaneFran..... 6-8

6-6 Failureof crawlspacefoundation,whichwasunderminedbyscour.......................................... 6-8

6-7 Typicalstemwallfoundation.................................................................................................... 6-10

6-8 FortMyersBeach,Florida:Oceanfronthouseconstructedonanopenfoundation................ 6-11

6-9 FortMyersBeach,Florida:Newlyconstructedhouseelevatedonanopenfoundation.......... 6-12

6-10 DauphinIsland,Alabama:SuccessfulpilefoundationfollowingHurricaneKatrina.............. 6-13

6-11 DauphinIsland,Alabama:Structurenearcollapseduetoinsufficientpileembedment......... 6-13

6-12 LongBeach,Mississippi:Structureremovedfromitsfoundationbywaveaction ................... 6-14

6-13 Pileinstallationmethods ........................................................................................................... 6-15

6-14 Diagonalbracingschematic...................................................................................................... 6-17

6-15Kneebraceconnectionexample .............................................................................................. 6-18

6-16Elevationview(right)of aconcretepilefoundationusinggradebeams.................................. 6-19

6-17 Successfuluseof abreakawaywall........................................................................................... 6-21

6-18 Buildingdamagesduetotheincorrectconstructionof abreakawaywall............................... 6-21

6-19 Possiblefailuremodesformasonrypiers.................................................................................. 6-22

6-20 PassChristian,Mississippi:Performancecomparisonof shallow,openfoundations............... 6-23

6-21 BelleFontainePoint,JacksonCounty,Mississippi:Columnconnectionfailure....................... 6-23

7-1 Loadtransferbetweendiaphragmsandshearwall .................................................................... 7-2
FEDERAL EMERGENCY MANAGEMENT AGENCY TOC-5

TABLE OF CONTENTS TOC

7-2 Horizontaldiaphragmanddiaphragmcomponents.................................................................. 7-3

7-3 Verticalshearwallsandshearwallcomponents......................................................................... 7-3

7-4 Lossof roof sheathingduetoinadequatefastening................................................................... 7-4

7-5 Exteriorviewsof connectionbetweenroof sheathingandroof trusses .................................... 7-6

7-6 Interiorviewsof connectionbetweenroof sheathingandroof trusses ..................................... 7-6

7-7 Detailof masonrywall-to-roof trusses ....................................................................................... 7-7

7-8 Horizontalloadingsexertedonexteriorwalls ............................................................................ 7-9

7-9Segmentedshearwalls.............................................................................................................. 7-10

7-10 Perforatedshearwalls ............................................................................................................... 7-10

7-11 Shearwallanchor ..................................................................................................................... 7-12

7-12 Exampleof balloonframing..................................................................................................... 7-13

7-13 Additionalbracingatagableendwall ..................................................................................... 7-13

7-14 Improperlybracedgablewalls.................................................................................................. 7-14

7-15 Residentialuseof amomentframe.......................................................................................... 7-15

7-16Upliftconnectionsaroundframedopening.............................................................................. 7-16

7-17 Designedof areinforcedmasonrywallsystem ........................................................................ 7-18

7-18 WoodenI-joistsusedforfloorframing ..................................................................................... 7-20

8-1 Instancewherewindpressuresexceededthestrengthof theasphaltroofing............................ 8-2

8-2 Gulfport,Mississippi:Windsdislodgedroof-mountedequipment............................................. 8-2

8-3 Exampleof anaugmentedunderlaymentinstallation ............................................................... 8-5

8-4 Exampleof propershingleinstallation....................................................................................... 8-6

8-5 Roof failuresthatresultedfromimproperstarter-stripinstallation............................................ 8-7

8-6 Roof failuresthatresultedfromasphaltshinglesbeinginstalledinarakingfashion................. 8-7

8-7 Lossof asphaltshingleroofingalonghip ................................................................................... 8-7

8-8 Claytileroof failure.Thetilesweredislodgedduetoinadequateanchorage ...........................8-8

8-9 Stormdamagetoatileroof system............................................................................................ 8-9

9-1 Examplesof moisturebarriersystems........................................................................................ 9-4

9-2 Examplesof moisturebarriersystems........................................................................................ 9-4

9-3 Propersidinglappingtopreventmoisturepenetration .............................................................. 9-5

9-4 Roof flashing............................................................................................................................... 9-7

9-5 Windowflashingdetails .............................................................................................................. 9-7
TOC-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

TOC TABLE OF CONTENTS

9-6 Comparisonof typicalhigh-windsidingversesstandardsiding ................................................ 9-8

9-7 Thecenterof thenailingslotistheproperfastenerlocation..................................................... 9-8

9-8 Properfastenerclearance............................................................................................................ 9-8

9-9 Exampleof woodsidingonawood-framedhouse .................................................................... 9-9

9-10 Figureillustratingthelayoutof bricktiesathouseunderconstruction ................................... 9-10

9-11 Waveland,Mississippi:Housewithcollapsedbrickveneerduetoinsufficientwallties........... 9-10

9-12 Exampleof anexteriorfloorcoveringsystemdamagedbyHurricaneIvan ........................... 9-11

10-1 PuntaGorda,Florida:Failureof aroof structurefrompressurization ...................................10-2

10-2 PuertoRico:Failureduetoinadequatepressureratingof window......................................... 10-3

10-3 PuntaGorda,Florida:Glazingfailureduetowindbornedebrisfromdisplacedroofing........ 10-3

10-4 Glazingfailureduetowindbornedebris.................................................................................. 10-3

10-5 Pensacola,Florida:Exampleof aninsufficientshutteringsystem ...........................................10-7

10-6 Pensacola,Florida:Failureof glazingfromwindbornedebris............................................... 10-10

10-7 PuntaGordaIsles,Florida:Anchoragefailureinslidingglassdoorfailure ........................... 10-12

10-8 Negativepressurefailureof garagedoor................................................................................ 10-15

10-9 Positivepressurefailureof garagedoor.................................................................................. 10-15

Tables

2-1 EnhancedFujitaScale .............................................................................................................. 2-20

2-2 Saffir-SimpsonHurricaneScale ............................................................................................... 2-22

2-3 WindPressureExampleforExposureB................................................................................... 2-26

2-4 WindPressureExampleforExposureC .................................................................................. 2-27

3-1 CodeCrosswalk ........................................................................................................................3-22

10-1 Tables2and3fromASTME1996 ..........................................................................................10-9

Appendix:................................................................................................................................................A-1
FEDERAL EMERGENCY MANAGEMENT AGENCY 1-1

INTRODUCTION 1

Introduction

Thedevastatingeffectsof recenthurricanesespeciallyhurricanesCharley(2004),Ivan(2004),Katrina

(2005),Rita(2005),andIke(2008)haveunderscoredthevulnerabilityof thenationscoastalareas.

Thisguideprovideslocalbuildingofficialsandfloodplainmanagerswithinformationaboutthedesign

andconstructionof hazard-resistantresidentialstructureswithinthecoastalenvironment.Theprimary

coastalhazardsthisguidewillhighlightarehighwindsandflooding.Thebuildingtypestheguidefocuses

onaredetachedsingle-family,attachedsingle-family(townhouses),andlow-risemulti-familystructures

(i.e.,thosecontainingthreeorfewerstories).Manyof theprinciplesdiscussedhereinalsoapplytononresidential

structures;however,thosestructuresarecoveredinotherFederalEmergencyManagement

Agency(FEMA)publications.

1.1 Objectives

Theprimaryobjectiveof thisguideistoassistlocalofficialsandcommunitydecisionmakersincoastal

areasinadoptingandimplementingsoundmitigationmeasurestolowerthevulnerabilityof buildings

todisasters.

Thegoalsof thisguideareto:

n Introduce

anddiscusshowrequirementsinthe2006editionsof theInternationalResidentialCode

(IRC)andInternationalBuildingCode(IBC)promotehazard-resistantdesignandconstructionin

coastalareas

n Recommend

buildingdesignandconstructiontechniquesthatcanimprovetheperformanceof 

structuresduringandafterfloodingandhigh-windevents

n Provide

guidanceforimplementingfloodingandhigh-windmitigationbestpracticesintotheprocess

of designingandconstructingresidentialbuildings

1.2 Target Audience

Thetargetaudienceof thispublicationisstateandlocalgovernmentofficialsworkingwithinthebuilding

sector.Theguideismeanttoassisttheminimplementingfloodplainmanagementrequirementswithin

thecoastalenvironment.Thisguidedescribesmitigationmeasuresandtheapplicationof buildingcode

requirementsthathavebeensuccessfulinthepastandcouldbeimplementedquickly,especiallyinareas

recoveringfromadisaster.Newhomesandhomesrepairedafterbeingdamagedbyfloodandwind

mustbeconstructedtocomplywithcurrentbuildingcodes,standardsandtheNationalFloodInsurance

Program(NFIP)regulations.

1.3 Scope

Thisguidepresentsanoverviewof theprincipalplanninganddesignconsiderationsforimproving

theperformanceof residentialbuildingsduringfloodingandhigh-windeventsandtheiraftermaths.

Itprovidesinformationthatdirectslocalofficialsonwheretofindresourcesfordesignguidanceand
1-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

1 INTRODUCTION

alsopresentspracticalrecommendationsforprotectingbuildingsandtheiroccupantsagainsthazards

typicallyfoundincoastalzones.

Somepeoplechoosetoliveinhigh-hazardareas,whileothersresidethereoutof necessity.Theintent

of thisguideistoprovidetechnicalinformationtolocalbuildingofficialswhooverseeconstructionin

theseareas.ThisinformationisFEMAsrecommendedbest-practicesforcoastalconstructionthatwhen

implementedshouldimprovebuildingsafetyandreducefuturelosses.Whilethisguidefocusesprimarily

onnewconstruction,theprinciplesdescribedhereinalsoapplytotherenovationof existingbuildings.

Theguideemphasizestheimportanceof incorporatingmitigationmeasuresagainstfloodingandhigh

windsintotheplanninganddesignof buildings.

Theguideprovidesreaderswithinformationaboutthenaturalforcesactinguponcoastalstructures

andthemethodsandprocessesavailabletoprotectthosestructures.Thisinformationis,bynecessity,

limited.Itisnotexpectedthatthereaderwouldbeabletousethisinformationdirectlytodevelopplans

andspecifications.Instead,itservesasanintroductiontothefundamentalsof riskmitigationplanning

anddesign.Thisguidewillaidbuildingofficialsandregulatoryprofessionalsastheyinteractwithdesign

professionals,procurementpersonnel,andprojectadministrators.Itwillalsohelptoprovideabetter

graspof planningandconstructiontechniquesthatwillaidbuildingofficialsandregulatoryprofessionals

astheyworktoimprovethesafetyandwelfareof theircoastalcommunities.

1.4 Using the Guide

Thisguideisgenerallydividedintothefollowingsections:

n An

initialexplanationof coastalhazards(Chapter2)

n An

introductiontoregulatoryrequirementsandinspectionissues(Chapters3and4)

n Evaluations

of variouscomponentsof residentialbuildingconstruction(Chapters5,6,7,8,9,

and10)

Whilethisguideisnotmeanttoserveasadesignmanual,itisintendedtohelpreadersunderstandthe

generalconceptof mitigatingcoastalhazardsanditsapplicabilitytobuildingcomponents.Whenever

possible,theguiderefersreaderstodesigncodesandstandardsandotherrelevantmaterials.Margin

notesprovideadditionalinformationorcallattentiontoimportantconcepts.

TheLocalOfficialsGuideforCoastalConstructionispartof afamilyof FEMAmitigationguidesandreports.

Thesepublicationsarereferencedwithintheguideinordertoassistthereaderinfindingotherhelpful

mitigationinformation.

FEMApublicationsreferredtointhisguide:

n FEMA,

CoastalConstructionManual:PrinciplesandPracticesof Planning,Siting,Designing,Constructing,and

MaintainingResidentialBuildingsinCoastalAreas,FEMA55(3rdEdition),Washington,DC,August2005

n FEMA,

ManufacturedHomeInstallationinFloodHazardAreas,FEMA85,Washington,DC,

September1985(arevisionisexpectedin2009)
FEDERAL EMERGENCY MANAGEMENT AGENCY 1-3

INTRODUCTION 1

n FEMA,

HomebuildersGuidetoEarthquakeResistantDesignandConstruction,FEMA232,Washington,DC,

August2008

n FEMA,

EngineeringPrinciplesandPracticesof RetrofittingFlood-proneStructures,FEMA259,Washington,DC,

January2001

n FEMA,

MitigationAssessmentTeamReport:HurricaneFraninNorthCarolina,FEMA290,Washington,DC,

April1997

n FEMA,

FloodplainManagementBulletinontheElevationCertificate,FEMA467-1,Washington,DC,

May2004

n FEMA,

MitigationAssessmentTeamReport:HurricaneCharleyinFlorida,FEMA488,Washington,DC,

April2005

n FEMA,

MitigationAssessmentTeamReport:HurricaneIvaninAlabamaandFlorida,FEMA489,Washington,

DC,August2005

n FEMA,

HomeBuildersGuidetoCoastalConstructionTechnicalFactSheetSeries,FEMA499,Washington,DC,

August2005

n FEMA,

DesignGuideforImprovingCriticalFacilitySafetyfromFloodingandHighWinds:ProvidingProtectionto

PeopleandBuildings,FEMA543,Washington,DC,January2007

n FEMA,

MitigationAssessmentTeamReport:HurricaneKatrinaintheGulf Coast,FEMA549,Washington,DC,

July2006

n FEMA,

RecommendedResidentialConstructionfortheGulf Coast:BuildingonStrongandSafeFoundations,FEMA

550,Washington,DC,July2006

n FEMA,

NFIPTechnicalBulletin1:OpeningsinFoundationWallsandWallsof Enclosures,FIA-TB-1,

Washington,DC,August2008

n FEMA,

NFIPTechnicalBulletin2:FloodDamage-ResistantMaterialsRequirementsforBuildingsLocatedin

SpecialFloodHazardAreas,FIA-TB-2,Washington,DC,August2008

n FEMA,

NFIPTechnicalBulletin5:Free-of-ObstructionsRequirementsforBuildingsLocatedinCoastalHigh

HazardAreas,FIA-TB-5,Washington,DC,August2008

n FEMA,

NFIPTechnicalBulletin9:DesignandConstructionGuidanceforBreakawayWallsBelowElevated

CoastalBuildings,FIA-TB-9,Washington,DC,August2008
1-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

1 INTRODUCTION

1.5 Coastal Construction versus Inland Construction

Coastalstructuresaresubjecttoextremehazardsandloads.Duetotheintensityof theseconditions,

coastalconstructioninvolvesadditionaldesignconsiderations:

n Wave

actionexertstremendousloadsuponthefoundationsof coastalstructures.Suchloadingshave

beenknowntocausesignificantdamagetothesestructures.

n Erosion

andscourcanremovesoil,causingunderminingof somefoundationsof residentialbuildings

andincreasingtheunbracedlengthonopenfoundations.Subsidenceandrisingseaandwaterlevels

canpotentiallyincreaseflooddepths,creatingadditionalfloodloadsontheresidentialstructure.

n Waterborne

debriscanexertanimpactandproducerepetitiveloadsnotseenininlandresidential

construction.

n Wind

speedsaretypicallyhigherincoastalareasandrequirestrongerengineeredbuildingconnections

andmorecloselyspacedfastenersof buildingsheathing,siding,androof systems.

n Wind-driven

rain,airbornesalts,corrosion,anddecayareconstantconcernswithincoastalareas.

Toaddresssuchdifferencesinloadingcriteria,homesincoastalareasmustbedesignedandbuiltto

withstandextremeconditions.Thisguideoutlinestheminimumbuildingrequirementsforstructures

andsuggestsbestpracticestoimproveastructuresresistancetofuturestormevents.Exceedingthese

minimumrequirementscanresultinseveraleconomicbenefits:

n Reduced

damageduringcoastalstormevents

n Reduced

buildingmaintenance

n Longer

buildinglifetime

n Improved

CommunityRatingSystem(CRS)score

n Reduced

insurancepremiums

Althoughthisguidediscussesindetailbuildingdesignandconstructionissues,italsoaddressesother

aspectsof coastalconstructionsuchasplanning,zoning,andachievingcompliancewithlocalordinances.

Theseconsiderationsarealsoimportantbecauseevenawell-builtbuildingcansustainsignificantdamage

orcollapseif itispoorlysited.Theimpactsof erosionandscourshouldbeseriouslyconsideredduring

theplanningprocess.
FEDERAL EMERGENCY MANAGEMENT AGENCY 1-5

INTRODUCTION 1

1.6 Building Codes

Thisguideprimarilyreferencestwocodes:TheInternationalBuildingCode(IBC)andtheInternational

ResidentialCode(IRC).AchievingfamiliaritywithotherrelevantmaterialsfromtheAmericanSocietyof 

CivilEngineers(ASCE)andregulationsfromtheNFIPisimportantwhenimplementingacomprehensive

approachtocoastalresidentialconstruction.Thestateinwhichthelocalofficialisworkingmayuse

othercodesorstandardsoneitherastateorlocallevel.If yourlocationdoesnotusethesecodes,this

guidewillstillprovideinsightintobestpracticesincoastalconstructionmethodsandsuggestappropriate

designconsiderations.

Codesreferredtointhisguideare:

n International

CodeCouncil,InternationalBuildingCode,CountryClubHills,IL,2006

n International

CodeCouncil,InternationalResidentialCode,CountryClubHills,IL,2006

n International

CodeCouncil,InternationalExistingBuildingCode,CountryClubHills,IL,2006

n NFPA,

BuildingConstructionandSafetyCode,NFPA5000,Quincy,MA,2005

Standardsreferredtointhisguideare:

n American

Societyof CivilEngineers,StructuralEngineeringInstitute,MinimumDesignLoadsforBuildings

andOtherStructures,ASCE/SEI7-05,Reston,VA,2005

n American

Societyof CivilEngineers,StructuralEngineeringInstitute,FloodResistantDesignand

Construction,ASCE/SEI24-05,Reston,VA,2005

n American

ConcreteInstitute/AmericanSocietyof CivilEngineers/TheMasonrySociety,BuildingCode

RequirementsforMasonryStructures,ACI530/ASCE5/TMS402,FarmingtonHills,MI,updated2008

n American

Forest&PaperAssociation,WoodFrameConstructionManualforOne-andTwo-FamilyDwellings

(WFCM),Washington,DC,2001

n American

IronandSteelInstitute,StandardforCold-FormedSteelFraming:PrescriptiveMethodforOne-and

Two-FamilyDwellings(COFS/PM)withsupplementtoStandardforCold-FormedSteelFramingÐ PrescriptiveMethod

forOne-andTwo-FamilyDwellings,AISIS230-07,Washington,DC,updated2007

n American

NationalStandardsInstitute(ANSI)/SinglePlyRoofingIndustry(SPRI),WindDesignStandard

forBallastedSingle-PlyRoofingSystems,ANSI/SPRIRP-4,Waltham,MA,2002

n ANSI/Door

andAccessSystemsManufacturersAssociation(DASMA),StandardMethodforTesting

SectionalGarageDoors:Determinationof StructuralPerformanceUnderUniformStaticAirPressureDifference,ANSI/

DASMA108,Waltham,MA
1-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

1 INTRODUCTION

n American

SocietyforTestingandMaterials(ASTM),StandardTestMethodforWind-Resistanceof Asphalt

Shingles(Fan-InducedMethod),ASTMD3161,WestConshohocken,PA

n ASTM,

StandardTestMethodforWindResistanceof AsphaltShingles(UpliftForce/UpliftResistanceMethod),

ASTMD7158,WestConshohocken,PA

n ASTM,

StandardTestMethodforStructuralPerformanceof ExteriorWindows,Doors,Skylights,andCurtainWalls

byUniformStaticAirPressureDifference,ASTME330,WestConshohocken,PA

n ASTM,

StandardTestMethodforPerformanceof ExteriorWindows,CurtainWalls,Doors,andImpactProtectiveSystems,

ImpactedbyMissile(s)andExposedtoCyclicPressureDifferentials,ASTME1886,WestConshohocken, PA

n ASTM,

StandardSpecificationforPerformanceof ExteriorWindows,CurtainWalls,Doors,andImpactProtective

SystemsImpactedbyWindborneDebrisinHurricanes,ASTME1996,WestConshohocken,PA

n ASTM,

StandardPracticeforInstallationof ExteriorWindows,Doors,andSkylights,ASTME2112,

WestConshohocken,PA

n American

ArchitecturalManufacturersAssociation/Window&DoorManufacturersAssociation/

CanadianStandardsAssociation,Standard/SpecificationforWindows,Doors,andUnitSkylights,

AAMA/WDMA/CSA101/I.S.2/A440,Schaumburg,IL,March2007

n National

FireProtectionAssociation(NFPA),ModelManufacturedHomeInstallationStandard,NFPA225,

Quincy,MA,2005

Additionalresourcesreferredtointhisguide:

n International

CodeCouncil,andFEMA,ReducingFloodLossesThroughtheInternationalCodeSeries:Meeting

theRequirementsof theNationalFloodInsuranceProgram(2ndEdition),CountryClubHills,IL,2005

n American

InstitutesforResearch,Evaluationof theNationalFloodInsuranceProgram,December2006

n Applied

TechnologyCouncil,ATC-45FieldManual:SafetyEvaluationof BuildingsAfterWindStormsand

Floods,RedwoodCity,CA,2007

n North

CarolinaStateUniversity/OregonStateUniversity,BehaviororBreakawayWallsSubjectedtoWave

Forces:AnalyticalandExperimentalStudies,Tungetal.,Raleigh,NC,1999
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-1

COASTAL HAZARDS AND CONSIDERATIONS 2

Coastal Hazards and 

Considerations

T

hischapterdescribesthehazardsassociatedwithcoastalareasandtheissuesthatlocalofficialsmust

considerwhentheyworkinthisenvironment.Thechapterenlightensthereaderonthefloodand

windhazardsassociatedwithcoastalareasandprovidesabrief summaryof otherhazardsthat

couldpotentiallyimpactconstructionmethodsattheendof thechapter.

2.1 Flood Hazards: General Design Considerations

Thissectionintroducesthephysicalnatureandcharacteristicsof coastalfloods.Italsodescribesthetypes

of flooddamagethatcanresultwhenbuildingsarelocatedwithincoastalfloodhazardareas.

2.1.1 The Nature of Flooding

FloodingisthemostcommonnaturalhazardtooccurintheUnitedStates,affectingmorethan20,000

localjurisdictionscoveredundertheNationalFloodInsuranceProgram(NFIP)andrepresentingmore

than70percentof presidentialdisasterdeclarations.Floodingisanaturalprocessthatmayoccurina

varietyof forms.Thisguidefocusesoncoastalfloodingfromhurricanesandtropicalstorms.Increased

developmentalongournationscoastlinescreatespotentiallylife-threateningsituationsandrenders

propertyvulnerabletoseriousdamageordestruction.

Floodingalongshorelinesisusuallytheresultof coastalstormsthatgeneratestormsurgeorwaves.Several

factorscanaffectthefrequencyandseverityof damagethatensuesasaresultof coastalflooding:

n Erosion

of shorelines,oftenresultinginsignificantlossesof soil

withasingleevent

n Rising

sealevels

n Deposition

of sedimentfromrecededwavesorwater,orsediment

thatiscarriedinlandbywaveaction

n Land

subsidence,whichincreasesflooddepths

n Failure

of leveesthatmayresultinthesuddenfloodingof areas

behindlevees

Coastalfloodinghasdistinctcharacteristicsthatshouldbeconsideredintheselectionof buildingsites,

designof newbuildings,andsubstantialrepairormodificationof existingfloodpronebuildings.

NOTE

Flood frequency analyses are 

performed using historical records and hydrological analysis, 

and the results are influenced 

by the length of the record. 

Such analyses do not account 

for recent changes to the land 

(such as shifting of barrier 

islands due to storms) or future 

changes (including development, 

greater subsidence, or 

climatic variations).
2-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

CoastalfloodingoccursalongtheAtlantic,Gulf,andPacificcoastsandmanylargelakes,includingthe

GreatLakes.Coastalfloodingisinfluencedbystormsurgesassociatedwithtropicalcyclonicweather

systems(e.g.,hurricanes,tropicalstorms,tropicaldepressions,andtyphoons),extratropicalsystems(i.e.,

noreasters),andtsunamis(whicharesurgesinducedbyseismicactivity).Coastalfloodingisprimarily

characterizedbywind-drivenwaves.Alongthereachesof theGreatLakes,windsblowingacrossbroad

expansesof watercangeneratewavesrivalingthoseof oceanshorelines.Figure2-1isaschematicof 

agenericcoastalfloodplain.Section2.1.3.1providesadditionalinformationondepthof floodingin

mappedareas.

Figure 2-1. 

Floodplain along an open coast. (Flood zones identified in this figure are discussed in Subsection 2.1.4.3 of this guide.)

2.1.2 Flood Characteristics and Loads

Characteristicsassociatedwithcoastalfloodingareimportantintheanalysisof sitesforbuildingsand

inthedeterminationof floodloadsthatmustbeconsideredaspartof thearchitecturalandengineering

design.Thesecharacteristicsaredescribedbelow.

Depth.Themostnoticeablecharacteristicof anyfloodiswaterdepth.Thedepthof coastalfloodingis

influencedbysuchfactorsasstormstrength,tidalcycle,stormduration,landelevation,andthepresence

of waves.Depthisacriticalfactorinbuildingdesignbecausethefloodforcesactinguponaverticalsurface

(suchasafoundationwall,column,post,pier,orpile)aredirectlyrelatedtodepth.Costsassociatedwith

protectingbuildingsfromfloodingtypicallyincreasewithdepth.Undercertainconditions,hurricanes

Flood Level Including

Wave Eects

100-Year 

Stillwater Elevation

Sea Level

Shoreline Limit of Flooding

and Waves

Wave Height 

<1.5 ft

Wave Height ≥ 3 ft Wave Height 3.0-1.5 ft

BFE -- Ground = 6 ft

at This Location BFE -- Ground = 3 ft

at This Location

Stillwater Depth 

< 2 ft

100-Year Stillwater Depth = D

D/2

Stillwater Depth

Between 4 and 2 ft

BFE

(D+D/2)

RECOMMENDED

REGULATED

V Zone Coastal A Zone A Zone X Zone

V Zone A Zone X Zone
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-3

COASTAL HAZARDS AND CONSIDERATIONS 2

canproducestorm-surgefloodingthatis20to30feetabovemeansealevelor,inextremecasesalongthe

Gulf Coast,asmuchas35feetabovemeansealevel(seeFigure2-2).Thesestorm-surgeeventscanresult

insignificantwaterdepthswithinlow-lyingcoastalareas.

Duration.Durationisdefinedastherecordedlengthof timeof abovenormalwaterlevels.Most

coastalfloodingisinfluencedbythenormaltidalcycleaswellashowfastcoastalstormsmovethrough

thatparticularregion.Areassubjecttocoastalfloodingcanexperiencelong-durationfloodinginwhich

drainageispoororslowasaresultof topographyorthepresenceof floodcontrolstructures.Forexample,

theremaybedepressionsinthelandthatcouldholdwaterorsituationsinwhichwatercouldbetrapped

behindafloodwallorleveewithinadequatedrainage.Morecommonly,coastalfloodingisof shorter

durationusually12to24hoursespeciallyif stormsmoverapidly.Forbuildingdesign,durationis

importantbecauseitaffectsaccess,buildingusability,saturationandstabilityof soils,andselectionof 

buildingmaterials.Inthemid-AtlanticandNewEnglandstates,however,noreasterscanresultinflooding

thatlastsformorethan3days.

Velocity.Floodwatervelocityrangesfromextremelyhigh(associatedwithstormsurgesof 10feetper

secondormore)toverylowornearlystagnant(inbackwaterareasandexpansivefloodplains).Inthis

context,velocityrefersnottothemotionassociatedwithbreakingwavesbuttothespeedof themass

movementof floodwateracrossanarea.Velocityisimportantinsiteplanningbecauseof thepotential

forerosion.Instructuraldesign,velocityisafactorindeterminingthehydrodynamic(i.e.,movingwater)

loadsandimpactloads(whichistheforceof movingwaterortheforceof floodbornedebrishitting

abuilding).

Waveaction.Wavescontributenotonlytoerosionandscourbutalsoaddsignificantlytotheloads

exertedonbuildings.Themagnitudeof waveforcescanbe10tomorethan100timesgreaterthanwind

andotherdesignloadsandthusmaycontrolmanydesignparameters.Wavesmustbeconsideredinsite

planningalongcoastalshorelines;wavesmustalsobeconsideredinfloodhazardareasthatareinlandof 

opencoastsandotherlocationswherewavesoccur,includingareaswithsufficientopenspacesthatwinds

Figure 2-2.

LONG BEACH, MISSISSIPPI: 

Aerial photo of apartment 

complex and surrounding 

area after Hurricane Katrina. 

(Source: FEMA 549)
2-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

cangeneratewaves(suchaslakesandexpansiveriverinefloodplains).Wavesontopof stormsurgesmay

beasmuchas50percenthigherthanthedepthof thesurge.Figures2-3,2-4,2-5,and2-6illustratethe

powerof waveactiononstructures.

Impactsfromdebris.Floatingdebriscontributestotheloadsthatmustbeconsideredinthestructure

design.Themethodsandmodelsusedtopredictanddelineatefloodhazardareasdonotspecifically

incorporatetheeffectsof debris.Fewsources,otherthanpastobservationsandengineeringjudgment,

areavailabletodeterminethepotentialeffectsof debrisimpactloads.Morerecentmodelbuildingcodes

requirethatfoundationsbedesignedtoresistarepresentativeimpactfromfloodbornedebris.

Figures 2-3 and 2-4.

GULF SHORES, WEST BEACH, 

ALABAMA: Insufficient pile 

embedment contributed to the 

displacement of houses. 

(Source: FEMA 489)

Figure 2-4
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-5

COASTAL HAZARDS AND CONSIDERATIONS 2

Figures 2-5 and 2-6.

ORANGE BEACH, ALABAMA: 

Collapse of five-story, multi-family 

buildings on shallow foundations.

(Source: FEMA 489)

Erosionandscour.Incoastalareas,erosionreferseithertotheloweringof thegroundsurfaceasaresult

of afloodeventorthegradualrecessionof ashorelineasaresultof long-termcoastalprocesses.Scour

referstoalocalizedloweringof thegroundsurfaceduetotheinteractionof currentsand/orwaveswith

structuralelements(suchaspilings).Soilcharacteristicsinfluenceanareassusceptibilitytoscour.Erosion

andscourmayaffectfoundationstabilityandthemaintainingof filledareasbyremovingallsupportfrom

beneathafoundation,resultinginpossiblestructuraldamageorbuildingcollapse.
2-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

Flood

Openings

No Flood

Openings

Lateral Hydrostatic

Pressure

Figure 2-7. Hydrostatic loads on buildings.

2.1.2.1 Hydrostatic Loads

Hydrostaticloadsoccurwhenwatercomesintocontactwithabuildingorbuildingcomponent,both

aboveandbelowthegroundlevel.Theseloadsmayactaslateralpressureorasupwardvertical

pressure(buoyancy).

Lateralhydrostaticloadsareadirectfunctionof waterdepth(seeFigure2-7).Theseloadscancausesevere

deflectionordisplacementof buildingsorbuildingcomponentsif thereisasubstantialdifferenceinwater

levelsonoppositesidesof thecomponent(suchastheinteriorandexteriorof abuilding).Hydrostatic

loadsarebalancedonthefoundationelementsof elevatedbuildings,suchaspiersandcolumns,because

theelementissurroundedbywater.Toreduceexcessivepressurefromstandingwater,minimumNFIP

requirementsinAZonesrequiretheuseof floodopeningsalongcontinuousfoundations,aswellasfor

enclosedareasbelowthefloodelevation.

NOTE

Flood openings are 

recommended to relieve most 

foundation hydrostatic loads. 

The number of openings 

required is related to the 

size of those openings and 

the size of the footprint 

of the structure. Properly 

designed flood openings 

will allow the water level to 

rise equally on either side of 

enclosed foundation walls.

Buoyancyforcesresultingfromthedisplacementof waterisalsoamatterof concern,especiallyfor

basements,dryswimmingpools,andabovegroundandundergroundtanks.Buoyancyforcesareresisted

bythedeadloadof thebuildingortheweightof thetank.Whendeterminingresistancetobuoyancy

forces,theweightsof occupantsorotherliveloadsarenotconsidered.If thebuildingortankdoesnot

weighenoughwhenempty,additionalstabilizingmeasuresmustbetakentopreventflotation.Further,

whencombiningloadsinthedesignprocess,typicallyonly60percentof thebuildingsdeadloadmay

beusedtoresistflood-relatedloading;thisbecomesasignificantconsiderationfordesignsintendedto

dryfloodproof abuilding.Itshouldbenotedthatbuoyancyforceisslightlygreaterinsaltwaterbecause

saltwaterismoredensethanfreshwater.

2.1.2.2 Hydrodynamic Loads

Waterflowingaroundabuildingorastructuralelementthatextendsbelowthefloodlevelimposes

hydrodynamicloads.Theloads,whichareafunctionof flowvelocityandstructuregeometry,include

frontalimpactontheupstreamface,dragalongthesides,andsuctiononthedownstreamside

(seeFigure2-8).
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-7

COASTAL HAZARDS AND CONSIDERATIONS 2

Thecomputationmethodsforhydrodynamicloadsareoutlinedin

thedesignstandardASCE7-05.Thosemethodsassumethatthe

floodvelocityisconstant(i.e.,steadystateflow)andthatthedynamic

loadimposedbyfloodwatersmovingatlessthan10feetpersecond

canbeconvertedtotheequivalenthydrostaticload.Accordingto

ASCE7-05,hydrodynamicloadsbecomeimportantwhenflowrate

exceeds5feetpersecond;forvelocitieslessthan5feetpersecond,

thestandardallowstheloadtobecalculatedasahydrostaticload,as

outlinedinASCE7-05Section5.4.2

2.1.2.3 Wave Loads

Whenwavesstrikebuildingelements,theforcecanbe10to100or

moretimeshigherthanwindandotherforces.Forcesof thismagnitude

canbesignificant,evenwhenactingovertherelativelysmallsurface

areaof theopenfoundationof anelevatedbuilding.Post-storm

damageinspectionsshowthatbreakingwaveloadsoverwhelmnearly

allwood-frameandunreinforcedmasonrywallsbelowthewave

crestelevation.Onlyengineeredandmassivestructuralelementsare

capableof withstandingbreakingwaveloads.

Therefore,inmostresidentialstructuredesign,thepreferredmethodof addressinghydrodynamicloads

istoraisethestructureabovetheexpecteddepthof flooding(includingwaves).Thehydrodynamicloads

canbesohighthatitisnotpossibletoresisttheminacost-effectivemanner.Themagnitudeof wave

forcesistherationalebehindthefloodplainmanagementrequirementforthebottomof thelowest

horizontalstructuralmemberof thelowestfloortobepositionedatorabovethedesignfloodelevation

inenvironmentswherewavesarepredictedtobe3feethighorhigher(i.e.,VZones).Baseduponthese

factors,theNFIPrequiresanopenfoundationdesignbeusedwithinVZones.

Themagnitudeof waveloadsdependsuponthewaveheight.Equationsforwaveheightarebasedupon

theassumptionthatwavesaredepth-limited(ontheorderof 78percentof stillwaterdepthinshallow

waterbreakareas)andthatwavespropagatingintoshallowwaterbreakwhenthewaveheightreaches

acertainproportionof theunderlyingstillwaterdepth.FEMAusestheseassumptionstodefinecoastal

Drag Effect on Sides

Frontal Impact on

Upstream Side

Negative Pressure/Suction on Downstream Side

Building or

Building Element

Depth of Water

Drag Effect on Sides

Frontal Impact on

Upstream Side FLOW

Figure 2-8.

Hydrodynamic loads on a building or 

building element. (Source: FEMA 543)

NOTE

Drag coefficients for common 

building elements, such as 

columns and piers, can be found 

in a number of sources. ASCE 

7-05 and FEMA 55 recommend 

some drag-coefficient values.

NOTE

While Coastal A Zones are 

not formally shown on Flood 

Insurance Rate Maps (FIRM), 

in A Zones where wave heights 

exceed 1.5 feet (such as Coastal 

A Zones), FEMA recommends 

using open foundations.
2-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

high-hazardareas(i.e.,VZones)wherebreakingwavesarepredicted

tobe3feethighorhigher.Atanygivensite,waveheightsmaybe

modifiedbyotherfactors.DesignersshouldrefertoASCE7-05for

adetaileddiscussionandcomputationprocedures.Asdescribed

inASCE7-05,designandconstructionof buildingsandother

structuressubjecttowaveloadsshallaccountforthefollowingloads:

wavesbreakingonanyportionof thebuildingorstructure;uplift

forcescausedbyshoalingwavesbeneathabuildingorstructure,or

portionthereof;waverunupstrikinganyportionof thebuildingor

structure;wave-induceddragandinertiaforces;andwave-induced

scouratthebaseof abuildingorstructure,oritsfoundation.

Breakingwaveloadsonverticalwallsorsupportingstructuralmembersreachamaximumwhenthe

directionof waveapproachisperpendicular.Itiscommontoassumethatthedirectionof approachwill

beperpendiculartotheshoreline,inwhichcasetheorientationof thewalltotheshorelinewillinfluence

thedirectionof approachusedinloadcalculations.ASCE7-05providesamethodforreducingbreakingwave

loadsonverticalwallsforwavesthatapproachabuildingfromadirectionotherthanstraight-on.

2.1.2.4 Debris Impact Loads

Debrisimpactloadsareimposedonabuildingorbuildingelementbyobjectscarriedbymovingwater.

Objectscommonlycarriedbyfloodwatersincludetrees,dislodgedtanks,andremnantsof structuressuch

asdocksandbuildings,asshowninFigures2-9,2-10,2-11,and2-12.Extremeimpactloadsresultfrom

lesscommonsources,suchasshippingcontainers,boats,andbarges.Themagnitudeof theseloadsis

difficulttopredict,yetsomereasonableallowanceisrequiredduringthedesignprocessif modelcodes

areineffect.

Figure 2-9.

GULFPORT, MISSISSIPPI: 

Floodborne debris, including shipping 

containers and sections of destroyed 

buildings. (Source: FEMA 549)

NOTE

Waves only 1.5 feet high can 

impose considerable loads and 

damage. A 1.5-foot-high wave 

can catastrophically fail the 

wall of a wood-frame (2 by 4) 

structure. As a result, there is a 

growing awareness of the value 

of considering waves in areas 

referred to as Coastal A Zones 

(see Subsection 2.1.4.3 of 

this guide).
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-9

COASTAL HAZARDS AND CONSIDERATIONS 2

Figure 2-10.

Example of surge, wave, and debris damage. 

(Source: FEMA 549) 

Figure 2-12.

BIG LAGOON, ALABAMA: Buildings constructed on piles and elevated several feet above the base flood elevation (BFE) 

sustained less flood damage than adjacent buildings at lower elevations. (Source: FEMA 489)

Figure 2-11.

Example of surge, wave, and debris damage. 

(Source: FEMA 489)
2-10 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

Thelocationof abuildingwithinthepotentialdebrisstreaminfluencesimpactloads.Thepotentialfor

debrisimpactsissignificantif abuildingislocatedimmediatelyadjacentto(ordownstreamfrom)other

buildings,amongcloselyspacedbuildings,ordownstreamfromlargefloatableobjects.Debrisimpacts

thosebuildingsthatarelocatedontheopencoastandshorelinesof backbays.

Debrismayimpactnotonlythefirstrowof buildings,butalsobuildingsseveralrowsback.Thebasic

equationtoestimatethemagnitudeof impactloadsdependsupondesigner-selectedvariablessuchas

coefficients,buildingorbuilding-elementstiffness,debrisweight,debrisvelocity,anddurationof impact.

Thelatterthreevariables(whicharedescribedindetailinASCE7-05)arebrieflydescribedbelow.

Whenreviewingplans,theinclusionof debrisloadsshouldconsiderimpactsonfoundationelementsfrom

debrisweighingatleast1,000pounds.Baseduponregionalconditions,thisnumbercouldincreasein

someareas.ChapterC5of ASCE7-05providessomebackgroundonimpactloadsandtheassumptions

madeincalculatingthem.Standardassumptionsaremadeformostcoastalandriverineareas.Special

provisionsareoutlinedforareassuchasthePacificNorthwest,wherelargetreesandlogsarecommon.

Thechapteralsoaddressessituationswhereloadslessthanthestandard1,000-poundimpactforceshould

beconsidered.Otherfactorstobeconsideredinthecalculationof debrisimpactloadsincludethedebris

velocity,whichisthevelocityof debriswhenitstrikesabuilding,andthedurationthatittakesthedebris

tostoponceitimpactsthebuilding.

2.1.2.5 Erosion and Local Scour

Erosionandscourcansignificantlyimpactbuildingperformanceandshouldthereforebeconsidered

duringthesiteevaluationanddesign.Incoastalareas,erosionmayaffectthegroundsurfaceandmay

causeashort-orlong-termrecessionof theshoreline.Inareassubjecttogradualerosionof theground

surface,additionalfoundation-embedmentdepthcanmitigatetheeffects.Whereshorelineerosionis

significant,however,engineeredsolutionsareunlikelytoproveeffective.Avoidanceof sitesinareassubject

toactiveerosionusuallyisasafeandcost-effectivesolution.Althougheverybuildingsiteisimportant,local

officialsshouldevaluateareasof knownlong-termshorelinerecessionandensurethatelectedofficialsare

awareof thepotentialimpactsof poorlysitedstructureswithintheseareas.

Localscourresultsfromturbulenceatthegroundlevelaroundfoundationelements.Determining

potentialscouriscriticalinthedesignof foundationstoensurethatfailureduringandafterflooding

doesnotoccurasaresultof thelossineitherbearingcapacityoranchoringresistancearoundtheposts,

piles,piers,columns,footings,orwalls.Scourcanalsoimpactabuildingslateralstability.Alossof 

lateralstabilitycanoftenoverstresspileconnectionswiththestructure,resultinginthefailureof weakor

improperlydesignedconnections.Inmanyinstances,deeperfoundationsarerecommendedtoaccount

forsignificantlossesinsoilandscour.Figures2-13,2-14,and2-15showthedramaticimpactsof erosion

onstructures.

Atsomelocations,soilatorbelowthegroundsurfacecanberesistanttolocalscour,andcalculatedscour

depthsbaseduponunconsolidatedsurfacesoilsbelowmaybeconsideredexcessive.Ininstanceswhere

thelocalofficialbelievestheunderlyingsoilatasitewillbescour-resistant,theofficialshouldrecommend

theassistanceof ageotechnicalengineerorgeologist.
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-11

COASTAL HAZARDS AND CONSIDERATIONS 2

Figures 2-14 and 2-15.

GULF SHORES, ALABAMA: House on pile foundation, adjacent to breach in the barrier island that experienced erosion 

and significant non-structural damage below the lowest floor. (Source: FEMA 489)

2.1.3 Design Parameters

Floodhazardsandfloodingcharacteristicsmustbeidentifiedtoevaluatetheimpactof sitedevelopment,

determinedesignparametersnecessarytocalculatefloodloads,designfloodproofingmeasures,and

identifyandprioritizeretrofitmeasuresforexistingbuildings.

Figure 2-13.

ORANGE BEACH, ALABAMA: Significant erosion caused a non-structural parking slab to fail and the structure to lean 

due to insufficient pile embedment. (Source: FEMA 489)
2-12 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

2.1.3.1 Flood Depth 

Becausenearlyeveryotherflood-loadcalculationdependsdirectlyor

indirectlyuponit,flooddepthisthemostimportantfactorrequired

tocomputeloadsexertedbyflooding.Thefirststepindetermining

flooddepthataspecificsiteistoidentifythefloodthatisspecified(i.e.,

thedesignevent),whichwilleitherbestatedinapplicableregulations

ormandatedbythegoverningauthority.Themostcommonflood

usedfordesignisthebaseflood(seeSubsection2.1.4of thisguide).

Basefloodelevations(BFE)aredeterminedinVandA Zonesasthe

designstillwaterflooddepthplustheadditionalwavecrestheight,

whichisanadditional55percentof thestillwaterdepth.Thesecond

stepistodeterminethegroundelevationatthesite.Becausethesepiecesof dataareusuallyobtained

fromdifferentsources,itisimportanttodeterminewhethertheyarebasedonthesameverticaldatum.

If theyarenot,standardcorrectionsmustbeapplied.

Figure 2-16.

Coastal wave height and 

stillwater depth.

(Source: FEMA 543)

Wave Crest 

Wave 

Height*

Wave Trough

Stillwater

Depth

Flood

Depth**

Ground (or Eroded Ground) Elevation

* Maximum wave height is 78 percent of stillwater depth

** Flood depth including waves is 55 percent greater than the stillwater depth

NOTE

When evaluating flood depths 

or elevations as related to house 

elevations, it is important to 

consider which vertical datum 

is being used. Newer FIRMs 

use the NAVD88 (while older 

maps use the NGVD29). This 

information, which is listed on 

the FIRM, is considered by 

the surveyor when structure 

elevations are taken.

NOTE

Waves and storm-induced 

erosion are most common in 

coastal areas. However, wide 

rivers and lakes may experience 

wind-driven waves, and erodible 

soils are found throughout the 

United States. For information 

about waves and erosion, 

see FEMA 55, Coastal 

Construction Manual.

Incoastalareas,thefloodelevationsshownonFloodInsuranceRateMaps(FIRMs)includethedepth

of wavesonlyif thepredictedwaveheightsaregreaterthan3feet.Intheseareas,shownasVZoneson

FIRMs(seeSubsection3.1.4.3of thisguide),theflooddepthiscomposedof astillwaterdepthplusthe

expectedheightof waves(seeFigure2-16).

TheFIRMsalsodelineatefloodhazardareasshownasAZones;thesezonesareinlandof VZonesor

locatedalongshorelineswherepredictedwaveheightsarelessthan3feet.Whenthegroundelevationis

subtractedfromthefloodelevation,theresultisthestillwaterdepth.Wherewavesareexpectedtorange

inheightfrom1.5feetto3feet(i.e.,intheCoastalAZone,asexplainedinSubsection2.1.4.3of this

guide),theloadingfromthewavesshouldbeincludedintheloadcalculations.Useof onlythestillwater

depthtodeterminethefloodloadswillresultinanunderestimateof theloads.Therelationshipshown

onFigure2-16shouldbeusedtoestimatewaveheightsasafunctionof stillwaterdepth.
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-13

COASTAL HAZARDS AND CONSIDERATIONS 2

Inareaswitherodiblesoils,localofficialsmustconsidertheeffectsof erosionwherefloodwaterslowerthe

groundsurfaceorcauselocalscouraroundfoundationelements.Theflooddepthdeterminedusingflood

elevationandgroundelevationshouldbeincreasedtoaccountforchangesinconditionsduringaflood

event.Loweringthegroundsurfaceeffectivelyresultsnotonlyindeeperwateragainstthefoundation;

itmayalsoremovesupportingsoilfromthefoundation,whichmustbeaccountedforinthefoundation

design.WhilefloodmapsandtheresultingBFEsaccountfortheerosionthatoccursduringabaseflood

event,theydonotconsiderlong-termerosion.Inaddition,themapsdonotaccountforsite-specific,

foundation-specificscour,whichshouldbeconsideredinthedesignprocess.

2.1.3.2 Flood Velocity

Estimatingfloodvelocitiesincoastalfloodhazardareasinvolvesconsiderableuncertainty,andlittle

reliablehistoricalinformationordatafromactualcoastalfloodeventsisavailable.Thedirectionand

velocityof floodwaterscanvarysignificantlythroughoutacoastalfloodevent.Floodwaterscanapproach

asitefromonedirectionasastormapproachesandthenshifttoanotherdirection(orseveraldirections)

asthestormmovesthroughthearea.Floodwaterscaninundatesomelow-lyingcoastalsitesfromboth

thefront(e.g.,ocean)andtheback(e.g.,bay,sound,orriver).Similarly,atanygivensite,flowvelocities

canvaryfromclosetozerotomorethan10feetpersecond.Forthesereasons,whendeterminingflood

loadsforbuildingdesign,velocitiesshouldbeestimatedconservatively,anditshouldbeassumedthat

floodwaterscanapproachfromthemostdesign-criticaldirection.

Despitetheuncertainties,therearemethodstoestimateapproximatecoastalfloodvelocities.One

commonmethodisbasedonthestillwaterdepth(i.e.,theflooddepthwithoutwaves).Localofficials

shouldverifythatdesignersconsideredthetopography,distancefromthefloodingsource,andproximity

tootherbuildingsandobstructionsbeforeselectingthefloodvelocityfordesign.Thosefactorscandirect

andconfinefloodwaters,witharesultingaccelerationof velocities.Thisincreaseinvelocitiesisdescribed

astheexpectedupperbound.Expectedlowerboundvelocitiesareexperiencedinareaswherethose

factorsarenotexpectedtoinfluencethedirectionandvelocityof floodwaters.

2.1.4 Flood Hazard Maps and Zones

FIRMsidentifyareassubjecttoflooding.Theselocationsincludethe

SpecialFloodHazardArea(SFHA)representingthelandwithinthe

floodplainwitha1percentannualchanceof flooding.Theflood

eventthatproducesthe1percentannualfloodisoftencalledthe100-

yearflood.FIRMsalsoincludeareasbetweenthe100-and500-year

floodsandthoseareasoutsidethosefloodextents.NFIP-prepared

mapsaretheminimumbasisof stateandlocalfloodplainregulatory

programs.FIRMsarepartof theprogramtoregulatedevelopmentwithinthefloodplain;inreturn,

propertyownersareofferedinsuranceprotectionagainstlossesfromflooding.Somecommunitiesbase

theirregulationsonafloodof recordorahistoricallysignificantfloodthatexceedsthebasefloodshown

onNFIPmaps.

TheFIRMsusedbytheauthorityhavingjurisdiction(AHJ)shouldbeconsultedduringplanningandsite

selection,sitedesign,andarchitecturalandengineeringdesign(whetherforthedesignof newbuildings

ortherehabilitationof existingbuildings).Regardlessof thefloodhazarddatarequiredforregulatory

NOTE

As of 2007, 60.3 percent of 

the U.S. population had digital 

geographic information system 

(GIS) flood data. It is projected 

that by the end of 2009, 92 

percent of the population will 

have digital GIS flood data.
2-14 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

purposes,additionalresearchshouldbeconductedonpastmajorfloodsandotherfactorsthatcouldlead

tomoresevereflooding,andhenceimpactthefloodriskataparticularsite.

2.1.4.1 The 100-year Flood

Therecurrenceintervalof afloodisanexpressionof frequencybasedonprobabilities.Thiscould

bedefinedasthelikelihoodthatanevent(inthiscase,aflood)of acertainmagnitudewilloccur

withinagivenperiod.ThefloodingeventcommonlyreferredtointheNFIPisthe100-yearflood.

Thisdesignationcanbedeceptiveandgivetheimpressionthatthistypeof eventwilloccuronly

onceevery100years.Whencalculated,the100-yearfloodhasa1percentchanceof occurringor

beingexceededwithinayear.Duetothisnumberbeingapercent-annualchance,itispossiblethata

comparablefloodcouldoccuratthesamelocationduringthenextyear,orcouldoccurevenmultiple

timesduringasingleyear.Thelawsof probabilitysuggestthatastimepasses,thechanceof oneof 

theseeventsoccurringwillincrease,asshowninFigure2-17.Notethatduringthe30-yearlifeof a

typicalmortgage,thereisa26percentchanceof experiencingabasefloodforbuildingslocatedin

afloodplain.

Probability of a

Flooding Event Over 

a 30-Year Period

Percent chance of one or more floods of a given magnitude being equalled or exceeded in a 30-year period.

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

96%

71%

45%

26%

6%

10

Year

25

Year

50

Year

500

Year

100

Year

Flood Magnitude

Source: U.S. Geological Survey, Guidelines for Determining Flood Flow Frequency,

Bulletin 17B (Appendix D). 

Figure 2-17.

Flood probability chart.

(Source: U.S. Geological Survey, 

Guidelines for Determining Flood Flow 

Frequency, Bulletin 17B (Appendix D)).

NOTE

Flood maps are available at the 

FEMA Map Store (http://www.

fema.gov). For a fee, copies 

may be ordered online or by 

calling (800) 358-9616. The 

Flood Insurance Study (FIS) 

and engineering analysis 

used to determine the flood 

hazard area may be ordered 

through the FEMA Web site. 

This information can also be 

viewed online or downloaded.

NOTE

The assigned frequency of 

a flood (e.g., 100-year) is 

independent of the number 

of years between actual 

occurrences. Hurricane Camille 

hit the Mississippi coast in 

1969 with storm surge flooding 

that far exceeded previous 

events, and Hurricane Katrina 

affected much of the same area. 

Although just 36 years apart, 

both storms produced flood 

levels significantly higher than 

the predicted “100-year flood.” 
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-15

COASTAL HAZARDS AND CONSIDERATIONS 2

Forcoastalareas,bothhistoricalstormsandsimulatedstormsurgemodelscanbeusedtopredictthe

probabilitythatfloodwaterswillrisetoacertainlevelandbeaccompaniedbywavesof certainheights.

Manycoastalstormswillproducestormsurgefloodingthat,dependingonlocaltopography,mayextend

inlandsignificantlyfartherthananticipatedforthe100-yearfloodandmayresultinflooddepthsgreater

thanthe100-yearflood.Statistically,suchextremestormsurgesoccurlessfrequentlythanthe100-year

floods,buttheirconsequencescanbecatastrophic.

Localofficialsshouldensurethatplanners,designers,andbuildersunderstandtherelationshipsbetweenthe

floodlevelsfordifferentfrequencyeventsandextremeevents,especiallyinhurricane-pronecommunities.

Thedifferenceinfloodlevelsmaybeextremeinsomesituations,dependingonlocalconditionsandthe

sourceof flooding.Inotherareas,thelowerprobabilityflooddepthsmaynotbemuchhigherthanthe

100-yearflood.

TheNFIPusesthe100-yearfloodasthebasisformappingfloodhazardsonregulatorymaps,forsetting

insurancerates,andforapplyingregulationstominimizefutureflooddamage(referredtoontheflood

mapsastheBFE).Theextentof the100-yearflood(orBFE)isgivenoneof severaldesignationsorzones

ontheFIRMandcollectivelyarereferredtoasSFHAs.TheSFHAsshowtheextentof theanticipated

100-yearfloodwhiletheindividualzonesprovidespecificorgeneralinformationwithregardtothe

expectedelevationof flooding.Theextentof theSFHAisalsousedasthestandardforexaminationof 

olderbuildingstodeterminewhichmeasurestoapplytoreducefuturedamage.

2.1.4.2 Flood Maps

TheNFIPproducesFIRMsformorethan20,000communities

nationwide.Thecurrenteffectivemapsaretypicallyavailablefor

viewingincommunityplanningorpermitoffices.Itisimportantto

usethemostrecentfloodhazardmapwhendeterminingsite-specific

floodhazardcharacteristics.AlthoughmanyFIRMsaremorethan

15yearsold,oftenoneormorepanelsorportionsof amappanel

havebeenrevisedandrepublished.Communitiesmustadoptrevised

mapstocontinueparticipatingintheNFIP.

SomeFIRMsdonotshowthe0.2-percent-annual-chancefloodhazard

area(500-yearfloodplain),andmanyFIRMsdonotprovidedetailed

informationaboutpredictedfloodelevationsalongeverybodyof 

water.Whenthisinformationisnotavailable,theFloodInsurance

Study(FIS)producedtosupporttheFIRMs(bycommunity)should

beused.If boththeFIRMandFISdataareinsufficient,additional

statisticalmethodsandengineeringanalysesmaybeneededto

determinethefloodproneareasandtheappropriatecharacteristics

of floodingrequiredforsitelayoutandbuildingdesign.

If aproposedbuildingsiteorexistingbuildingisaffectedbyflooding,asite-specifictopographicsurveyis

criticaltodelineatethelandthatisbelowthefloodelevationusedforplanningpurposes.If detailedflood

elevationinformationisnotavailable,afloodplainstudymayberequiredtoidentifytheimportantflood

characteristicsanddatarequiredforsounddesign.

WARNING

Flood Insurance Rate Maps 

are used for insurance 

rating purposes; they are 

not comprehensive tools 

to identify all hazards 

associated with floods and 

the probabilities of occurrence 

at a particular risk site.

NOTE

Some areas have adopted a 

Design Flood Elevation (DFE). 

This is additional elevation, 

known as freeboard, above 

the Base Flood Elevation to 

account for variables and 

changes to future flood maps. 

Buildings in these jurisdictions 

may need to be built to a 

DFE, which will exceed the 

100-year flood elevation.
2-16 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

HavingfloodhazardareasdelineatedonaFIRMshouldnotoversimplifytheprocessof understanding

thehazard.Floodmapshavelimitationsthatshouldbeconsidered,especiallyduringsiteselectionand

design.Somewell-knownlimitationsareidentifiedbelow.

n Flood

hazardareasareapproximationsbasedonprobabilities;thefloodelevationsshownandtheareas

delineatedshouldnotbetakenasabsolutes,inpartbecausetheyarebasedonnumericalapproximations

of therealworld.

n Especially

foroldermaps,thetopographyusedtodelineatethefloodboundarymayhavehadcontour

intervalsof 5,10,oreven20feet(versus1or2feet),whichsignificantlyaffectstheprecisionwithwhich

theboundaryisdetermined.Theactualelevationof thegroundrelativetothefloodelevationiscritical,

asopposedtowhetheranareaisshownasbeinginoroutof themappedfloodhazardarea.

n The

scaleof mapsmayimpedeprecisedeterminations(manyoldermapsare1inch=2,000feet).

n Flooding

characteristicsmayhavebeenalteredbydevelopment,sometimesbylocalmodificationsthat

havealteredtheshapeof thelandsurfaceof thefloodplain(suchasfillsorlevees).

n Local

conditionsarenotreflected,especiallyconditionsthatchangeregularly,suchas

shorelineerosion.

n Areas

exposedtoverylowprobabilityfloodingarenotshown,suchasfloodingfromextremehurricane

stormsurges,extremeriverineflooding,damfailures,orovertopping(orfailure)of levees.

WhileFIRMsconsiderstorm-inducederosionassociatedwithasingle

100-yearflood,theydonotcaptureerosionpotentialatasite.Theyalso

donotconsiderthepotentialforwaterbornedebrisorsubsidence.

Regardlessof theirlimitations,floodmapsarevaluabletools;however,

additionaldatashouldbeconsideredwhenevaluatingthehazard.

Evaluatinghazardsassociatedwithfloodmapsisjustonecomponent

of effectivelymitigatingthehazardposedbyfloodwaters.

DigitalFloodInsuranceRateMaps(DFIRMs)arethecurrentformatinwhichFIRMsarebeingproduced.

Thisnewdigitalformatutilizesageographicinformationsystemenvironmentandwillreplacetheexisting

manuallyproducedFIRMs.Thisnewformatprovidesamoreinteractiveformatthatwillbeassociatedwith

databasesthatwillallowadditionalinformationtobeaccessed.ThisinformationwillincludetheFISdata

includingthehydrologicandhydraulicmodelsusedtoproducethestudy.Additionaldatasuchasbenchmarks,

structurerelateddataandaerialphotographoverlayswillprovidetheuserwithmoreinformationinamore

expeditiousmanner.

NOTE

A Flood Insurance Study (FIS) 

is an examination, evaluation, 

and determination of flood 

hazards and, if appropriate, the 

corresponding water-surface 

elevations. This information 

is used to develop FIRMs.
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-17

COASTAL HAZARDS AND CONSIDERATIONS 2

X Zone

A Zone

(Regulated)

V Zone

(Regulated)

Coastal

A Zone

(Recommened)

landward limit of 1.5-ft breaking wave height

Figure 2-18.

Example of a Digital Flood 

Insurance Rate Map (DFIRM). 

Figure 2-19.

Coastal flood hazard areas. 

2.1.4.3 NFIP Flood Zones

NFIP-preparedFIRMsshowdifferentfloodzonestodelineatedifferentfloodplaincharacteristics

(seeFigure2-18).ThefloodzonesshownontheFIRMs,andsomeotherdesignations,aredescribed

below.Figure2-19showstherelationshipsof floodzonestoeachother.

VZones.Alsoknownascoastalhigh-hazardareas,theseSFHAsaresubjecttohigh-velocitywaveaction.

VZonesarerelativelynarrowareasalongopencoastlinesandsomelargelakeshoresthataresubjectto

high-velocitywaveactionfromstormsorseismicsources.VZonesextendfromoffshoretotheinland

limitof aprimaryfrontalduneortoaninlandlimitwherethepredictedheightof breakingwavesdrops

below3feetorawaverun-updepthof lessthan3feet.

NOTE

Advisory Base Flood Elevations 

(ABFE) are sometimes 

developed after a specific 

event. These maps are based 

on surveyed high-water marks 

and inundation limits, but not 

the 500-year flood hazard 

area. Upon the issuance of a 

Recovery Advisory, these may 

be used in lieu of existing BFEs.

NOTE

Current editions of the building 

codes refer to ASCE 7-05 

and ASCE 24-05; both design 

standards include requirements 

for Coastal A Zones

(see Chapter 3 of this guide).
2-18 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

VEandV1-V30.AlsocallednumberedVZones,thesedesignationsareusedforSFHAswhere

engineeringanalyseshaveproduceddetailedfloodelevationsandboundariesforthebaseflood

(1-percent-annual-chanceflood).BFEsareprovided.

AZones.AlsocalledunnumberedAZonesorapproximateAZones,thisdesignationisusedforSFHAs

whereengineeringanalyseshavenotbeenperformedtodevelopdetailedfloodelevations.BFEsarenot

provided.Additionalengineeringanalysesandsite-specificassessmentsusuallyarerequiredtodetermine

theBFE.

AEZonesorA1-A30Zones.AlsocallednumberedAZones,thesedesignationsareusedforSFHAs

whereengineeringanalyseshaveproduceddetailedfloodelevationsandboundariesforthebaseflood

(1-percent-annual-chanceflood).BFEsareprovidedforriverinewaterwayswithinthesezones.AnFIS

willincludelongitudinalprofilesshowingwatersurfaceelevationsfordifferentfrequencyfloodevents.

AOandAHZones.Thesezonesincludeareasof shallowfloodingandaregenerallyshownwhere

theflooddepthaveragesfrom1to3feet,aclearlydefinedchanneldoesnotexist,thepathof flooding

isunpredictable,andvelocityflowmaybeevident.Thesezonesarecharacterizedbypondingor

sheetflow.BFEsmaybeprovidedforAHZones;flooddepthsmaybespecifiedinAOZones.Incoastal

areas,AOZonesaremostcommononthelandwardsideof dunes.

CoastalAZones.ThesezonesarenotnotedonFIRMs;however,theyhavebeennotedasbeing

clearlydefinedzoneswherebreakingwavesarebetween3feetand1.5feet.Theindicationof the

Limitof ModerateWaveAction(LiMWA)onmanyof therecentFIRMsisagoodindicationof the

locationof aCoastalAZone.ALiMWAistheapproximatelandwardlimitof the1.5feetbreaking

wave.BecauseCoastalAZonesarenotdelineatedonFIRMs,itisnecessarytodeterminewhetherthe

requiredconditionsarelikelytooccuratasite.Theuseof CoastalAZonesiseitherbylocaladoption

oratthediscretionof theAHJ.

ShadedX(orB)Zones.Thesezonesshowareasof the500-yearflood(0.2percent-annual-chance

flood)orareasprotectedbyfloodcontrollevees.ThesezonesarenotshownonmanyNFIPmaps;however,

theirabsencedoesnotimplythatfloodingof thisfrequencywillnotoccur.Withmapmodernization

projectsunderway,theBZonedesignationwillnotbeusedafter2010.

UnshadedX(orC)Zones.Thesezonesarealllandareasnotmappedasfloodhazardareas;theyare

outsideof thefloodplainthatisdesignatedforthepurposesof regulatingdevelopmentpursuanttothe

NFIP.Withmapmodernizationprojectsunderway,theCZonedesignationwillnotbeusedafter2010.

LeveeCertification.SpecialattentionshouldbepaidtotheFIRMinareaswithstructuresbehind

alevee.Whenreviewingareasbehindlevees,thestatusof theleveeshouldbeconsidered.TheNotes

toUserssectionontheFIRMexplainstheleveestatusatthetimeof mappublication.Additional

informationontheleveecertificationprocessisinFEMAProcedureMemorandumNo.43,Guidelinesfor

IdentifyingProvisionallyAccreditedLevees.
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-19

COASTAL HAZARDS AND CONSIDERATIONS 2

2.2 Wind Hazards: General Design Considerations 

Evenawell-designed,constructed,andmaintainedbuildingmaybedamagedinawindeventstrongerthan

thedesignwindspeed.Mostdamageoccursbecausebuildingelementshavelimitedwindresistancedue

toinadequatedesign,poorinstallation,ormaterialdeterioration.Althoughthemagnitudeandfrequency

of strongwindstormsvarybylocale,allbuildingsshouldbedesigned,constructed,andmaintainedto

minimizeandresistwinddamage.

Numerousexamplesof bestpracticespertainingtonewandexistingbuildingsarepresentedinthisguide

asrecommendeddesignandconstructionguidelines.Incorporatingthosepracticesapplicabletospecific

projectswillresultingreaterwindresistancereliabilityandwillthereforedecreaseexpendituresforrepair

of wind-damagedbuildingsandprovideenhancedprotectionforoccupants.

2.2.1 Primary Storm Types

Avarietyof windstormeventsoccursincoastalareasof theUnitedStates.Characteristicsof stormtypes

thatcanaffectthesiteshouldbeconsideredbythedesigner.Primarystormtypesaredescribedbelow.

Straight-linewind.Thiswindtypeisnormallygeneratedbythunderstorms.Straight-linewind

intensitiescanbesimilartothoseof atornado.Incontrasttoatornado,whichproduceswindsinarotating

motion,straight-linewindspushinonedirection.Highwindsassociatedwithintenselowpressurecan

lastforapproximatelyadayatagivenlocation.Althoughitismorecommoninsomeareas,straight-line

windscanoccuranywherethroughouttheUnitedStatesanditsterritories.1

Thunderstorm.Thunderstormscanformrapidlyandproducehighwindspeeds.Approximately

10,000severethunderstormsoccurintheUnitedStateseachyear,typicallyinthespringandsummer,

andtheyaremostcommonintheSoutheastandMidwest.Inadditiontoproducinghighwinds,they

oftencreateheavyrainandsometimesspawntornadoesandhailstorms.Thunderstormscommonlymove

throughanarearapidly,causinghighwindsforonlyafewminutesatagivenlocation.Theycanalsostall

andbecomevirtuallystationary.

Downburst.Alsoknownasamicroburst,thisisapowerfuldowndraftassociatedwithathunderstorm.

Whenthedowndraftreachestheground,itspreadsouthorizontallyandmayformoneormorehorizontal

vortexringsaroundthedowndraft.Theoutflowistypically6,000to12,000feetacross,andthevortex

ringmayrise2,000feetabovetheground.Thelifecycleof adownburstisusually15to20minutes.

Observationssuggestthatapproximately5percentof allthunderstormsproducedownbursts,whichcan

resultinsignificantdamageinlocalizedareas.Itisnotuncommonfortheuntrainedobservertomistake

downburstdamageastornadodamage.

Noreaster(northeaster).Anoreasterisacyclonicstormoccurringoff theeastcoastof North

America.Theseweatherevents(typicallyoccurringinthewinterseason)arenotoriousforproducingheavy

snow,rain,highwaves,andwind.Anoreastergetsitsnamefromthecontinuouslystrongnortheasterly

windsblowinginfromtheoceanaheadof thestormandoverthecoastalareas.Thesestormsmaylast

forseveraldays.

1 U.S. territories include American Samoa, Guam, Northern Mariana Islands, Puerto Rico, and the U.S. 

Virgin Islands. ASCE 7-05 provides basic wind speed criteria for all but Northern Mariana Islands.
2-20 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

Tornado.Tornadoesareviolentlyrotatingcolumnsof airextendingfromthebaseof athunderstorm

totheground.Althoughthewindspeedatagivenbuildingsitemightnotbegreat,abuildingonthe

peripherycouldstillbeimpactedbymanylargepiecesof windbornedebris.Tornadoesareresponsible

forthegreatestnumberof thenationswind-relateddeathseachyear.However,tornadofrequency,

occurrence,andwindspeedsarenotconsideredbythewindmapsof theIBC,IRC,andASCEusedto

identifythebasic(design)windspeedataparticularsite.

Buildingsthatarewell-designed,well-constructed,andwellmaintained

shouldhavelittleif anydamagefromweaktornadoes,

exceptforwindowbreakage.However,weaktornadoesoftencause

buildingenvelopedamagebecausemanybuildingshaveinherent

vulnerabilitiestowindandwindbornedebris.Mostbuildings

experiencesignificantdamageif theyareinthepathof astrong

orviolenttornadobecausetheytypicallyarenotdesignedforthis

stormtype.Asof February2007,tornadoesarenowclassifiedbythe

EnhancedFujitaScaleshowninTable2-1.

EF-SCALE DAMAGE LEVEL WIND SPEED 

(3-SEC GUST)

TYPE OF DAMAGE DONE

EF0 Light 65–85 mph Peels surface off of some roofs; some damage to gutters or siding; 

branches broken off trees; shallow-rooted trees pushed over.

EF1 Moderate 86–110 mph Roofs severely stripped; mobile homes overturned or badly damaged; 

loss of exterior doors; windows and other glass broken.

EF2 Considerable 111–135 mph

Roofs torn off well-constructed houses; foundations of frame homes 

shifted; mobile homes completely destroyed; large trees snapped or 

uprooted; light-object missiles generated; cars lifted off ground.

EF3 Severe 136–165 mph

Entire stories of well-constructed houses destroyed; severe damage 

to large buildings such as shopping malls; trains overturned; trees 

debarked; heavy cars lifted off the ground and thrown; structures with 

weak foundations blown away some distance.

EF4 Devastating 166–200 mph Well-constructed houses and entire frame houses completely

leveled; cars thrown and small missiles generated.

EF5 Incredible >200 mph

Strong frame houses leveled off foundations and swept away; 

automobile-sized missiles fly through the air in excess of 100 yards; 

high-rise buildings have significant structural deformation; incredible 

phenomena occurs.

NOTE

ASCE 7-05 defines “Special 

Wind Region” as an area where 

the basic wind speed shall 

be increased where records 

or experience indicate that 

the wind speeds are higher 

than normal. These regions 

consist of mountainous terrain, 

gorges, and other special 

topographic features.

Table 2-1. Enhanced Fujita Scale.

Source: National Oceanic and Atmospheric Administration
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-21

COASTAL HAZARDS AND CONSIDERATIONS 2

Hurricane.Ahurricaneisasystemof spiralingwindsconvergingwithincreasingspeedtowardthe

stormscenter(theeyeof thehurricane).Hurricanesformoverwarmoceanwaters.Thediameterof 

thestormvariesfrom50milesto600miles.Ahurricanesforwardmovement(translationalspeed)can

varybetweenapproximately5mphtomorethan25mph.Besidesbeingcapableof deliveringextremely

strongwindsforseveralhoursandmoderatelystrongwindsforadayormore,manyhurricanesalsobring

heavyrainfall.Hurricanescanalsospawntornadoes.

Of allthestormtypes,hurricaneshavethegreatestpotentialfordevastatingalargegeographicalarea

and,hence,affectingthegreatestnumberof people.Thetermshurricane,cyclone,andtyphoondescribe

thesametypeof storm.Thetermuseddependsontheregionof theworldwherethestormoccurs.

Figure2-20showshurricane-proneregionsof theUnitedStates.Table2-2presentstheSaffir-Simpson

scaleusedtoclassifyhurricaneintensity.Thetableshowswindspeedsforthedifferentcategoriesasboth

sustainedwindsandgustspeeds.Hurricanefrequency,occurrence,andwindspeedsareconsideredby

theIBC,IRC,andASCEwhenproducingwindmapsthatidentifythebasic(design)windspeedata

givensite.AdditionalinformationisprovidedinSection2.2.1.3.

Special Wind Region

Hurricane-Prone Region

Figure 2-20.

Hurricane-prone regions and special wind regions. (Source: Adapted from ASCE 7-05)
2-22 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

NOTE

The Saffir-Simpson Hurricane 

Scale categorizes hurricanes 

based on sustained wind 

speeds. Storm surge is not 

always correlated with the 

category because other 

factors influence surge 

elevations, notably forward 

speed of the storm, tide 

cycle, offshore bathymetry, 

and land topography.

Strength Sustained Wind Speed 

(mph)

1 minute sustained 

wind over water

Gust Wind Speed

(mph)

3 second gust 

over open water

Gust Wind Speed

(mph)

3 second gust 

over open ground

Pressure

(millibar)

Description

Cat 1 74–95 91–116 82–108 >979

Storm surge 4 to 5 feet above normal; 

no real building damage; unanchored 

mobile homes damaged.

Cat 2 96–110 117–140 109–130 965–979

Storm surge 6 to 8 feet above normal; 

some roofing, door, and window 

damage; considerable damage to 

mobile homes.

Cat 3 111–130 141–165 131–156 945–964

Storm surge 9 to 12 feet above normal; 

some structural damage to small 

residences and utility buildings with 

minor curtain wall damage; mobile 

homes destroyed.

Cat 4 131–155 166–195 157–191 920–944

More extensive curtainwall failures 

with some complete roof structure 

failures on small residences; complete 

destruction of mobile homes.

Cat 5 >155 >195 >191 <920

Complete roof failure on many 

residences and industrial buildings; 

some complete building failures 

with small utility buildings blown 

over or away; complete destruction 

of mobile homes.

Table 2-2. Saffir-Simpson Hurricane Scale
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-23

COASTAL HAZARDS AND CONSIDERATIONS 2

2.2.1.1 Windborne Debris

Duringanylargewindeventheavyobjectscanbecomeairborne.Theseobjectsposesignificanthazards

tothesurroundingbuildings.Designcriteriainthecurrentmodelbuildingcodestakethesehazards

intoaccountbyrequiringprotectionsystemsforglazedopeningsdevelopedtoresistsmall(rocks,

roofingmaterial,andsmallbranches)andlarge(trees,signs,andposts)impactsfromwindbornedebris

(commonlyreferredtoasmissiles).Theseobjectstypicallyimpactallportionsof abuildingandcause

damagetodoors,glazing,exteriorsiding,androofs.Constructionmethodsthatdonotaccountformissile

impactscanresultinabreachof thebuildingenvelopeandsubsequentlycauseadditionaldamageto

thestructureduetowindloading.Protectionof glazingfromwindbornedebrisimpactisrequiredbased

uponyourproximitytothecoastandthebasicwindspeedatasite.Additionalinformationisprovidedin

Chapter10.

2.2.1.2 Rainfall Penetration

Highwindsimpactbuildingsinmanyways.Inadditiontoloadingfromthewindandwindbornedebris,

whentheyarecoupledwithrainevents,significantwaterintrusionproblemscanoccur.Portionsof the

buildingenvelopethathavebeendesignedtoshedrainmaybecompromisedbywind-drivenrain.

2.2.1.3 Wind/Building Interactions

Whenwindinteractswithabuilding,bothpositiveandnegativepressuresoccursimultaneously(see

Figure2-21).Topreventwind-inducedbuildingfailure,buildingsmusthavesufficientstrengthto

resisttheappliedloadsfromthesepressures.Loadsexertedonthebuildingenvelopearetransferred

tothestructuralsystem,wheretheyinturnmustbetransferredthroughthefoundationintothe

ground,orbuildingdamagemayresult.Chapter5of thisguidehasadetaileddiscussionof loadpaths

andtheimportanceof loadpathcontinuity.Themagnitudeof thepressureisafunctionof several

primaryfactors:exposure,basicwindspeed,topography,buildingheight,buildingshape,andinternal

pressureclassification.

Suction on Side

Walls

WIND

Suction on Rear Wall

Positive Pressure on 

Front Wall

Uplift on Roof

Figure 2-21.

Wind-induced pressures on a 

building. (Source: FEMA 543)

NOTE

For information on exposure, 

see ASCE 7-05, Chapter 

6 Commentary, which 

includes aerial photographs 

of the different terrain 

conditions associated with 

Exposures B, C, and D.
2-24 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

Basicwindspeed.ASCE7-05specifiesthebasic(design)windspeedfordeterminingdesignwind

loadsatabuildingsite.ThebasicwindspeedismappedforthecontinentalU.S.andprovidedforother

islandsandU.S.territoriesat33feetabovegradeinExposureC(flatopenterrain).If abuildingislocated

inanExposureBorDarea,ratherthanaCarea,anadjustmentfortheactualexposureismadeinthe

ASCE7-05calculationprocedurewhenwindpressuresarecalculated.

Sincethe1995editionof ASCE7,thebasicwindspeedmeasurementhasbeena3-secondgustspeed.

Before1995,thebasicwindspeedwasafastest-milespeed(i.e.,thespeedaveragedoverthetimerequired

foramile-longcolumnof airtopassafixedpoint)2

.Mostof theUnitedStateshasabasicwindspeedof 

90mph3

,butmuchhigherspeedsoccurinAlaskaandinhurricane-proneregions.Thehighestbasicwind

speedspecifiedontheASCE7-05map170mphisinGuam.Hurricane-proneregionsaredefinedin

ASCE7-05tobetheAtlanticandGulf coastalareaswherethebasicwindspeedisgreaterthan90mph,

Hawaii,andtheU.S.territoriesintheCaribbeanandSouthPacific(seeFigure2-20).

BasicWindSpeed. ThedesignvaluesusedtobeginthewindloadcalculationsusingASCE7-05.This

windspeedvalueismeasuredataheightof 33feet(10meters)abovegradeandforanExposureC.

ASCE7-05requiresthatthebuildingbedesignedtosustainthisbasicwindspeedfromanydirection.

3-secondgust.Themeasurementof windspeedaveragedovera3secondperiod.Theshortdurationof 

theaverageiswhyitisreferredtoasagust.

Fastestmile. Theaveragespeedfora1-mile-longcolumnof airtopassananemometer.

(NowanobsoletetermandnolongerusedbytheNationalWeatherService.)

TheSaffir-SimpsonHurricaneScale(Table2-2)measuressustainedwindsthatareaveragedover1

minute.Therefore,thesewindspeedsarenotequivalenttofastestmileor3-secondgustwindspeeds

usedbythecodes.Themeasurementsaretakenoveropenwater.Toconvertthisinformationintoa3-

secondgust,aconversionmustbemadetothesustainedwindsoverlandandthenfurtherconvertedto

the3-secondgustusingtheDurstcurve(seeASCE7-05).ASCE7-05,CommentaryC6,explainsthe

conversionof sustainedwindoverwatertosustainedwindoverland.

Intheformulasusedtodeterminewindpressures,thebasicwindspeedissquared.Therefore,asthewind

speedincreases,thepressuresactingonabuildingareexponentiallyincreased,asshowninFigure2-22.

Figure2-22alsoillustratestherelativedifferenceinpressuresexertedontheMainWindForceResisting

System(MWFRS)andthecomponentsandcladding(C&C)elementsof buildings.Higherwindscan

producevorticescreatingveryhighlocalpressuresonC&C.Thesepressuresonroofing,roof sheathing

andsidingsarelocalizedandmuchgreaterthanthatonthemainframingmembers.Drawingsshould

providespecificdetailingandfasteningof roofing,roof sheathing,andsidingintheseareas.

Exposure.Terraincharacteristics(i.e.,groundroughnessandsurfaceirregularitiesinthevicinityof a

building)influencewindloading.ASCE7-05definesthreeexposurecategories:ExposuresB,C,andD,

withExposureBbeingtheroughestterraincategoryandExposureDbeingthesmoothest.

2

Gust speeds are about 15 mph to 20 mph higher than fastest-mile speeds (e.g., a 90 mph peak basic wind speed is equivalent 

to a 76 mph fastest-mile wind speed). International Building Code, Chapter 16, has a table of equivalent basic wind speeds.

3

Unless otherwise noted, wind speeds in this guide are presented as 3-second gust wind speeds with exposure C at 33 feet 

above grade.
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-25

COASTAL HAZARDS AND CONSIDERATIONS 2

Roof Corner Pressures - C&C

Roof Corner Pressures - MWFRS

Velocity - mph (3-second gust)

Pressure (psf - presented as absolute values)

ExposureBincludesurban,suburban,andwoodedareas.ExposureCincludesflat,openterrainwith

scatteredobstructionsandareasadjacenttowatersurfacesinhurricane-proneregions(whicharedefined

aboveunderbasicwindspeed).ExposureDincludesareasadjacenttowatersurfacesoutsidehurricaneprone

regions,mudflats,saltflats,andunbrokenice.Becauseof thewaveconditionsgeneratedby

hurricanes,areasadjacenttowatersurfacesinhurricane-proneregionsareconsideredtobeExposureC

ratherthanthesmootherExposureD.Thesmoothertheterrain,thegreaterthewindpressure;therefore,

buildingsinExposureCareaswouldreceivehigherwindloadsthanthoseinExposureBareas,atthe

samebasicwindspeed.

Topography.Abruptchangesintopography,suchasisolatedhills,ridges,andescarpments,causewind

tospeedup.Abuildinglocatedneararidgewouldreceivehigherwindpressuresthanabuildinglocated

onrelativelyflatland;insomecases,thewindpressuresmaybetwicethoseonflatareas.ASCE7-05has

aproceduretoaccountfortopographicinfluences.

Buildingheight.Windspeedataparticularsiteincreaseswithheightaboveground.Tallerbuildings

areexposedtohigherwindspeedsandgreaterwindpressures.ASCE7-05containsaprocedureto

accountforbuildingheightduringthecalculationof windpressures.

Forbuildingsof lowerheights(suchasthosefoundincoastalareas),elevatingorraisingthebuildingto

accountforfloodhazardswillincreasethewindpressuresactingonthebuilding.However,thisincreaseis

relativelysmall.Tables2-3and2-4providewindpressureinformationforfivelocationsonahypothetical

buildinglocatedonasitewithabasicwindspeedof 120mph.Thewindpressuresweredeterminedusing

theprescriptivetablesfromASCE7-05forlow-risebuildings(ASCE7-05,Figures6-2and6-3).

Figure 2-22.

Wind pressure as a function of wind speed. (Source: FEMA 543)
2-26 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

Table 2-3. Wind Pressure Example for Exposure B

Specifically,forhomessitedwheretheterrainsurroundingthebuildingisconsideredExposureB(see

ASCE7-05),Table2-3showsthereisnochangetothewindpressuresif themeanroof heightisincreased

fromanelevation15feetabovegroundto30feetaboveground.Ingeneral,asthebuildingheight

increasesinany5-footincrement(from30feetto35feet,from35feetto40feet,orfrom40feetto45

feet),theincreaseinpressuresisapproximately5percent.If theelevationincreasewasachangeof 10

feet,theincreaseinpressuresisapproximately8percent,whileanincreasein30feetwouldresultina

changeinpressuresof approximately10percent.Consideringthateventhelargestpressureincrease

associatedwitha30-footelevationchangeresultsonlyinanincreaseof 7psf,theimpacttothebuilding

designandcostwouldbeminimalforconnectorsormemberstowithstandthesenewwindpressures.

Similarly,Table2-4providesthesamecomparisonforabuildingsitedinExposureC.Theprimary

differenceisthatwindpressureswillbegintoincreaseasthemeanroof heightisincreasedfrom15

feetto20feet(approximately6percent).However,afterthisinitialincrease,theincreaseinpressures

forelevationchangesof 5feetand10feetarelessthanthoseinTable2-3forExposureBconditions,

approximately3.5percentand6percent,respectively.Althoughthetotalincreaseinwindpressurefor

somebuildingcomponentsmayincrease20percentif thebuildingelevationisincreased30feet,this

isnotaprobablescenario.Inmostcases,thebuildingmaybeelevated10or15feethigherthanitwas

originallyconstructed.Theincreaseinwindpressuresfrom15to30feetabovegradewouldonlybe13.5

percent.Again,asconnectorsandlargememberswouldberequiredtocarrytheloadsforthebasicwind

speedatthesite,anincreaseinpressureof 5to12psf forselectbuildingcomponentswouldhaveminimal

impactonthebuildingdesignorcostbecauseconnectorsandotherfastenerswouldhavebeenrequired

forthebuildingatthissiteregardlessof height.

ThesetablesalsohighlightthedifferencesbetweenwindloadsinExposureBandCareas.If asiteis

improperlyclassifiedasExposureB,thebuildingmaybeunderdesignedbyasmuchas30to40percent

(basedoncomparativeC&Cloads.)

Meanroof heightMWFRS C&C

abovegradein

ExpB Wall Roof Wall

Zone5 Roof Zone1 Roof Zone3

(feet) (psf)* (psf) (psf) (psf) (psf)

15 21.10 -19.10 -34.70 -23.70 -61.00

20 21.10 -19.10 -34.70 -23.70 -61.00

25 21.10 -19.10 -34.70 -23.70 -61.00

30 21.10 -19.10 -34.70 -23.70 -61.00

35 22.16 -20.06 -36.44 -24.89 -64.05

40 23.00 -20.82 -37.82 -25.83 -66.49

45 23.63 -21.39 -38.64 -26.54 -68.32

TableNotes(applicableforeachtable)

1.Windpressurescalculatedforasquarebuilding,approximately20ftby20ft

2.Roof slope=20degrees(assumed)

3.Effectivewindarea=10sf (forC&Cwindpressures)

4.Thehighestelevationprovidedisforameanroof heightof 45feetabovegrade.

Thetableswereendedatthisheightasthatisacommonzoninglimitusedfor

theheightof residentialstructuresincoastalareas.

*(psf)poundspersquarefoot
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-27

COASTAL HAZARDS AND CONSIDERATIONS 2

Table 2-4. Wind Pressure Example for Exposure C

Buildingshape.Aswindflowsoverandaroundabuilding,theresultantpressuresactingonitarea

functionof thebuildingshapeanditsorientationtothewind.Exteriorwallstypicallyhavelowerloads

thantheroof.Theends(edges)of wallshavehighersuctionloadsthantheportionof wallbetweenthe

ends.However,whenthewallisloadedwithpositivepressure,theentirewallisuniformlyloaded.Figure

2-23showstheseaerodynamicinfluences.ThenegativevaluesshownonFigure2-24indicatesuction

pressureactingupwardfromtheroof surfaceandoutwardfromthewallsurface.Positivevaluesindicate

positivepressureactinginwardonthewallsurface.Positivecoefficientsrepresentapositive(inward

acting)pressure,andnegativecoefficientsrepresentnegative(outwardacting[suction])pressure.Building

irregularities,suchasentryways,corners,baywindowprojections,stairtowersprojectingfrommain

walls,dormers,andchimneyscanallcauselocalizedturbulence.Turbulencecauseswindtospeedup,

whichincreasesthewindloadsinthevicinityof thebuildingirregularity.Simplystated,itcanbeassumed

thatatlocationswherebuildinggeometrychanges,pressureswillincrease.Theseareasmayincludewall

corners,roof edges,corners,andoverhangs.

Internalpressure(buildingpressurization/depressurization).Thebuildingportionthatkeeps

theelementsawayfrombuildingoccupantsistypicallyreferredtoasthebuildingenvelope.Openings

throughthebuildingenvelope,incombinationwithwindinteractingwithabuilding,cancauseeitheran

increaseinthepressurewithinthebuilding(i.e.,positiveinternalpressure)oradecreaseinthepressure

(i.e.,negativeinternalpressure).Gapsordisconnectsinthebuildingenvelopetypicallyoccuraround

openingssuchasdoorsandwindowframes,andbyairinfiltrationthroughwallsthatarenotcompletely

airtight.Adoororwindowleftopen,orglazingthatisbrokenduringastorm,cangreatlyinfluence

themagnitudeof theinternalpressureandmayexposethebuildingtowindforcesitwasnotdesigned

toresist.

Meanroof heightMWFRS C&C

abovegradein

ExpC Wall Roof Wall

Zone5 Roof Zone1 Roof Zone3

(feet) (psf)* (psf) (psf) (psf) (psf)

15 25.53 -23.11 -41.90 -28.68 -73.81

20 27.22 -24.64 -44.76 -30.57 -78.69

25 28.49 -25.79 -46.85 -32.00 -82.35

30 29.54 -26.74 -48.58 -33.18 -85.40

35 30.60 -27.70 -50.32 -34.37 -88.45

40 31.44 -28.46 -51.70 -35.31 -90.80

45 32.28 -29.22 -53.09 -36.26 -93.33

TableNotes(applicableforeachtable)

1.Windpressurescalculatedforasquarebuilding,approximately20ftby20ft

2.Roof slope=20degrees(assumed)

3.Effectivewindarea=10sf (forC&Cwindpressures)

4.Thehighestelevationprovidedisforameanroof heightof 45feetabovegrade.

Thetableswereendedatthisheightasthatisacommonzoninglimitusedfor

theheightof residentialstructuresincoastalareas.

*(psf)poundspersquarefoot
2-28 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

NOTE: Arrows indicate direction and magnitude of applied force.

Section

Plan

Positive Internal Pressure

Positive Internal Pressure

Figure 2-23.

Internal pressure condition when the dominant opening is in the windward wall. (Source: FEMA 543)
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-29

COASTAL HAZARDS AND CONSIDERATIONS 2

Figure 2-24.

Internal pressure condition when the dominant opening is in the leeward wall. (Source: FEMA 543)

Suction

Suction

Negative Internal Pressure

Negative Internal Pressure

NOTE: Arrows indicate direction and magnitude of applied force.

Section

Plan
2-30 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

Windstrikingexteriorwallsexertsapositivepressureonthewall,whichforcesairthroughunprotected

openingsandintotheinteriorof thebuilding.Atthesametimethatthewindwardwallisreceiving

positivepressure,thesideandrearwallsareexperiencingnegative(suction)pressurefromwindsmoving

aroundthebuilding.Thisisinpartduetothelackof high-pressureairontheoutsideof therearwall.

Asmoreairisforcedintothebuildingthroughtheunprotectedopenings,thebuildingbeginstobulgeor

becomepressurized.Thebuildingwillcontinuetopressurizeastheairfindsareasof lowerpressureand

escapesontherear(leeward)sideof thebuilding.Unprotectedopeningscanbebreachedontheleeward

side(oppositethewind)of buildingsduetonegativepressure(suction).Thiscancausetheoppositeeffect,

andastructuremaycollapseduetoalackof internalairpressure.

Whenabuildingispressurized,theinternalpressurepushesupontheroof.Thispushfrombelowthe

roof iscombinedwithsuctionontheroof fromabove,resultinginanincreasedupwardwindpressure

ontheroof.Theinternalpressurealsopushesonthesideandrearwalls.Thisoutwardpushiscombined

withthesuctionontheexteriorsideof thesewalls(seeFigures2-25and2-26).Thebreachingof asmall

windowcanbesufficienttocausefullpressurizationof thefacilitysinterior.Whenabuildingbecomes

fullypressurized(e.g.,duetowindowbreakageorsoffitfailure),theloadsappliedtotheexteriorwalls

androof aresignificantlyincreased.Therapidbuildupof internalpressurecanalsoblowdowninterior

partitionsandblowsuspendedceilingpanelsoutof theirsupportinggrid.

Whenabuildingisdepressurized,theinternalpressurepullstheroof down,thusreducingtheuplift

exertedontheroof.Thedecreasedinternalpressurealsopullsinwardonthewindwardwall,which

increasesthewindloadingonthatwall.

TheASCE7-05winddesignprocedureaccountsfortheinfluenceof internalpressureonthewalland

roof loads,anditprovidespositiveandnegativeinternalpressurecoefficientsforuseinloadcalculations.

Buildingsthataredesignedtoaccommodatefullpressurizationarereferredtoaspartiallyenclosed

buildings.AccordingtothecriteriainASCE7-05,thepresenceof openings(doors,windows,andvents)

onexteriorwallsandsurfacesof thebuildingdeterminewhetherabuildingcanbeconsideredenclosed,

partiallyenclosedoropen.Oncetheappropriatedesignationhasbeenselected,thebuildingisdesigned

forthepressuresassociatedwiththedesignation.Typically,buildingsthatareintendedtoexperienceonly

limitedinternalpressurizationarereferredtoasenclosedbuildings.Buildingsthatdonotexperience

internalpressurizationarereferredtoasopenbuildings(suchascoveredwalkwaysandmostparking

garages).Itshouldbenoted,thatthe2006IBCandIRClimittheuseof partiallyenclosedbuildings

withoutopeningprotectioninhurricane-proneregions.
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-31

COASTAL HAZARDS AND CONSIDERATIONS 2

Figure 2-25.

OCEAN SPRINGS, MISSISSIPPI: Apartment complex severely damaged by wind. Although wind speeds were less than 

current code-specified values, widespread severe damage occurred at this development, a result of poor construction 

quality. (Source: FEMA 549)

Figure 2-26.

GULF SHORES, ALABAMA: Partition walls destroyed by interior pressurization due to window damage. (Source: FEMA 489)
2-32 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

2 COASTAL HAZARDS AND CONSIDERATIONS

2.3 Other Hazards

Duringanystormeventthereexiststhepotentialforothertypesof 

hazards.Thesehazardscanbecausedeitherbythestormeventorbe

totallyindependentof it.Ineithercase,theirpotentialimpactsshould

beconsideredinthedesignof thestructure.

Earthquakeandseismicevents.Seismiceventscanoccuron

boththewestandeastcoasts.Sucheventscancauseliquefaction(soilfailures),surfacefaultruptures,slope

failures,orspurtsunamis.Localofficialsincoastalareaswithpotentialforseismiceventsshouldconsider

thesepossibilitieswhenreviewingbuildingplans.Whilemostbuildingofficialsinseismicareasareaware

of thebuildingconsiderationsnecessary,coastalareaspresentparticularchallenges.Theneedtoelevate

buildingstopreventwavesandinfiltrationfromfloodwatersanddamagefromfloodbornedebrisadds

challengestostabilizethemfromthemovementinducedbyanearthquake.Modelbuildingcodesand

guidancefromFEMAthroughtheNationalEarthquakeHazardReductionProgram(NEHRP)provide

coderequirementsandbestpracticesinregionswithseismicactivity.Additionalguidanceonthedesign

of residentialbuildingsinseismicareasisprovidedinFEMA232,HomebuildersGuidetoEarthquake-Resistant

DesignandConstruction.

Tsunamis.Long-periodwaterwavesgeneratedbyunderseashallow-focusearthquakesorbytectonic

platemovements,landslides,orvolcanicactivityarereferredtoastsunamis.Tsunamiscantravelgreat

distancesindeepwaterandcangrowquitelargewhentheyreachshallowcoastalareas.Designingforor

resistingwaveloadsfortsunamismaybedifficultandexpensive.

Indoorairquality.Afterastormevent,moldcangrowquicklyandpresentmajorhumanhealth

hazards.Moldandmildewarepresenteverywherebutneedexcessivemoistureandafoodsourceto

becomeproblematic.Long-termpoweroutagesafterstormsandalackof airflowfromnon-operating

HVACsystemspreventmoistareasinsidehousesfromdryingout.Thepossibilityformoldpropagation

shouldbeconsideredasapotentialhazardwhenresidentialstructuresarerebuiltafterstormevents.If 

moldissuspected,airqualityexpertsshouldbecontactedtoensurethatpropermitigationtechniquesare

used.Informationisavailableathttp://www.epa.gov/mold/moldresources.html.Additionalinformation

canbefoundinFEMA 549,MitigationAssessmentTeamReport:HurricaneKatrinaintheGulf Coast,Building

PerformanceObservations,Recommendations,andTechnicalGuidance.

Leveefailure.TheUnitedStateshasthousandsof milesof levees.Leveescanfailinthreeways:a

breachorbreakinthelevee,waterseepingunderneaththeleveeanderuptingontheotherside(calleda

boil),andovertoppingorfloodwatersexceedingtheheightof thelevee.Eachof thesefailuresisusually

triggeredbyexcessiverainsorstormsurges.Residentialstructuresprotectedbyleveesshouldbeevaluated

fortheirsusceptibilitytoleveefailurebecausemostareashavebeenmapped(toshowfloodzones),

assumingtheleveesremainintactandfunctional.Leveefailurescanoftenbeworsethanstandardstorm

surgeorrainfloodingduetothewaterbeingtrappedorcontained.Anexampleof thedevastatingeffects

of leveefailureisshowninFigure2-27.

NOTE

Additional information on 

publications from the National 

Earthquake Hazard Reduction 

Program (NEHRP) publications 

are available at http://www.fema.

gov/plan/prevent/index.shtm
FEDERAL EMERGENCY MANAGEMENT AGENCY 2-33

COASTAL HAZARDS AND CONSIDERATIONS 2

Figure 2-27.

NEW ORLEANS, LOUISIANA: Neighborhood with homes flooded and cars covered. In the background is a breached levee 

with water entering the area. (Source: FEMA 549)

FEDERAL EMERGENCY MANAGEMENT AGENCY 3-1

InvestIgatIng RegulatoRy RequIRements 3

Investigating Regulatory 

Requirements 

States

andcommunitiesenforceregulatoryrequirementsthat

determinewhereandhowbuildingsmaybesited,designed,

andconstructed.Theserequirementsincludethoseassociated

withprogramsestablishedbyfederalandstatestatutes,buildingcodes

andstandards,andlocallyadoptedfloodplainmanagementandland

useordinancesandlaws.

Thischapterbeginswithadiscussionof theNFIP.Theremainingsectionsexplainhowtomeetthe

minimumrequirementsthroughenforcementof the2006editionsof theIBCandIRC,standardsASCE

7-05and24-05,andotherregulatorydocuments.Thechapteroutlinesminimumflood-andwind-design

requirementsforhazard-resistantconstruction.Laterchaptersdetailtheserequirementsandprovide

examplesof bestpracticestomeetorexceedtheserequirements.

3.1 Floodplain Management Requirements 

and Building Codes

TheNFIPisthebasisfortheminimumrequirementsincluded

inmodelbuildingcodesandstandardsforflood-resistantdesign

andconstructionmethodsusedtowithstandflooddamage.FEMA

managestheNFIP,whichisintendedtoreducethelossof lifeand

damagecausedbyfloodsandflood-relatedhazards.Theoriginal

authorizinglegislationfortheNFIPistheNationalFloodInsurance

Actof 1968(42U.S.C.4001etseq.).Inthatact,theU.S.Congress

expresslyfoundthataprogramof floodinsurancecanpromotethe

publicinterestbyencouragingsoundlandusebyminimizingexposure

of propertytofloodlosses....

Themostconvincingevidenceof theeffectivenessof theNFIP

minimumrequirementsisfoundinfloodinsuranceclaimpaymentstatistics.Buildingsthatpre-datethe

NFIPrequirementsweregenerallynotconstructedtoresistflooddamageandbuildingsthatpost-datethe

NFIParedesignedtoresistflooddamage.TheNFIPaggregatelossdataindicatesthatbuildingsmeeting

theminimumrequirementsexperience80-percentlessflooddamagethanbuildingsthatpre-datethe

NFIP.Ampleevidencesuggeststhatbuildingsdesignedtoexceedtheminimumrequirementsareeven

lesslikelytosustaindamage.

Note

Unless otherwise noted, 

citations for the I-Codes in this 

guide refer to the 2006 editions.

Note

This guide does not cover 

manufactured housing. 

For NFIP requirements 

concerning manufactured 

housing, see § 60.3 of the 

regulations, and FEMA 85, 

Manufactured Home Installation 

in Flood Hazard Areas. Other 

relevant reference materials 

include NFPA 225, Model 

Manufactured Home Installation 

Standard, 2005 Edition and 

publications produced by 

U.S. Department of Housing 

and Urban Development.
3-2 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

3.1.1 Overview of the National Flood Insurance Program

TheNFIPisbaseduponthepremisethattheFederalgovernmentwillmakefloodinsuranceavailablein

communitiesthatadoptandenforcefloodplainmanagementregulationsthatmeetorexceedtheminimum

NFIPrequirements.Whendecisionsresultindevelopmentwithinfloodhazardareas,applicationof 

thecriteriaof theNFIPareintendedtominimizeexposureandflood-relateddamage.Stateandlocal

governmentsareresponsibleforapplyingtheprovisionsof theNFIPthroughtheregulatorypermitting

processes.AttheFederallevel,theNFIPismanagedbyFEMAandhasthreemainfunctions:

n Requires

communitiestoadoptfloodplainmanagementregulationstominimizeflooddamages

tonewbuildingsandthosebuildingsthatundergosubstantialimprovementsorthathavebeen

substantiallydamaged.

n Provides

floodplainmanagementcriteriafordevelopment,whichestablishtheminimumrequirements

tobeappliedtodevelopmentwithinmappedfloodhazardareas.Theintentistorecognizehazardsin

theentirelanddevelopmentprocess.

n Offers

floodinsurance,whichprovidessomefinancialprotectionforpropertyownerstocovercosts

associatedwithflood-relateddamagetobuildingsandcontents.

TheNFIPprovisionsguidedevelopmenttolower-riskareasbyrequiringcompliancewithperformance

measurestominimizeexposureof newbuildingsandbuildingsthatundergomajorrenovationor

expansion(calledsubstantialimprovementorrepairof substantialdamage).Thisachievesthelongterm

objectiveof buildingdisaster-resistantcommunities.

SubstantialImprovement.Anyrepair,reconstruction,rehabilitation,addition,orimprovementof a

buildingorstructure,thecostof whichequalsorexceeds50percentof themarketvalueof thestructure

beforetheimprovementorrepairisstarted.If thestructurehassustainedsubstantialdamage,anyrepairs

areconsideredsubstantialimprovementsregardlessof theactualrepairworkperformed.Thetermdoes

not,however,includeeither:

n Any

projectforimprovementof abuildingrequiredtocorrectexistinghealth,sanitary,orsafety

codeviolationsidentifiedbythebuildingofficialandthataretheminimumnecessarytoassuresafe

livingconditions.

n Any

alterationof ahistoricstructure,providedthatthealterationwillnotprecludethestructures

continueddesignationasahistoricstructure.

SubstantialDamage.Damageof anyoriginsustainedbyastructurewherebythecostof restoringthe

structuretoitsbefore-damagedconditionwouldequalorexceed50percentof themarketvalueof the

structurebeforethedamageoccurred.
FEDERAL EMERGENCY MANAGEMENT AGENCY 3-3

InvestIgatIng RegulatoRy RequIRements 3

3.1.2 Summary of the NFIP Minimum Requirements 

Performancerequirementsof theNFIParesetforthinFederal

Regulation44,Codeof FederalRegulations(CFR),Part60.The

requirementsapplytoalltypesof development,whichtheNFIP

broadlydefinestoincludebuildingsandstructures,sitework,roads

andbridges,andotherrelatedactivities.Residentialbuildingsmustbe

designedandconstructedtoresistflooddamage,andthatresistanceis

primarilyachievedthroughelevation.Additionalspecificrequirements

applytoexistingdevelopmentsespeciallyexistingbuildings.Existing

buildingsthatareproposedforsubstantialimprovement,including

restorationfollowingsubstantialdamage,aresubjecttotheregulations.

AlthoughNFIPregulationsfocusprimarilyonhowtobuild

structures,oneof thelong-termobjectivesof theprogramis

toguidedevelopmenttolesshazardouslocations.Preparing

floodhazardmapsandmakingtheinformationavailableto

thepublicisafundamentalstepinsatisfyingthatobjective.

Withthatinformation,interestedpartiescanmakeinformeddecisionsaboutwheretobuild,how

tousesitedesigntominimizeexposuretoflooding,andhowtodesignbuildingsthatwillresist

flooddamage.

Communityfloodplainmanagementordinancesandlawsmustincluderequirementsconcerningthe

followingtypesof buildingsintheSFHA,includingthoseinbothAZonesandVZones:newlyconstructed

buildings,substantiallydamagedbuildings,andsubstantiallyimprovedbuildings.Additionalrequirements

mustapplytonewsubdivisionsandotherdevelopmentwithintheSFHA.

Recognizingthegreaterhazardposedbybreakingwavesof 3feethighorhigher,FEMAhasestablished

thefollowingminimumNFIPregulatoryrequirementsfornewlyconstructed,substantiallydamaged,and

substantiallyimprovedbuildingslocatedinaVZone.Theserequirementsaremorestringentthanthe

minimumrequirementsforAZonebuildings:

n Only

open-foundationtypesareallowed.

n The

structureorbuildingmustbeelevatedsuchthatthelowest

horizontalstructuralmemberisconstructedatorabovetheBFE.

n Buildings

mustbedesignedandconstructedtoresistsimultaneous

windandfloodloads.

n Building

designsmustbecertifiedbyanengineer.

Note

Communities participating in 

the NFIP are encouraged to 

adopt and enforce floodplain 

management ordinances or 

laws that include requirements 

more stringent than the 

minimum requirements of 

NFIP regulations. For example, 

approximately 60 percent of 

NFIP participating communities 

require that buildings be 

elevated above, rather than 

simply to, the BFE. The 

additional elevation required 

is referred to as freeboard. 

(See note box on page 2-15 

and Section 4.3). See Chapter 6 

for the application of freeboard 

into foundation design.

Note

“Reasonably safe from 

flooding” is defined as a 

situation in which base flood 

waters will not inundate the 

land or damage existing or 

proposed structures. This would 

include any subsurface waters 

related to the base flood.
3-4 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

Thelocationof abuildinginrelationtotheAZone/VZone

boundaryonaFIRMcanaffectthebuildingdesign.Abuildingor

otherstructurethathasanyportionof itsfoundationinaVZone

mustbebuilttocomplywithVZonerequirements.Forbestpractices,

theseVZonerequirementsshouldbeconsideredforadoption

withinCoastalAZonesinordertoimprovebuildingperformance.

ThesubsectionsbelowsummarizetheminimumNFIPregulatory

requirementsandprovidedetailedinformationonV,A,andCoastal

AZonerequirements.

3.1.3 Minimum Requirements for All Buildings 

in All SFHAs 

Theminimumfloodplainmanagementrequirementsapplyto

allSFHAslocatedincommunitiesparticipatingintheNFIP.

Therequirementsaffectbuildings,subdivisions,andothernew

development;newandreplacementwatersupplysystems;andnewandreplacementsanitarysewage

systems.Belowisasummaryof someimportantaspectsof 44CFRPart60.3,aspresentedintheCode:

SiteDesign

TheNFIPsbroadperformancerequirementsforsiteworkinfloodhazardareasareshownbelow.

n Building

sitesshallbereasonablysafefromflooding.

n Adequate

sitedrainageshallbeprovidedtoreduceexposuretoflooding.

n New

andreplacementsanitarysewagesystemsshallbedesignedtominimizeoreliminateinfiltrationof 

floodwatersintothesystems,aswellasdischargesfromthesystemsintofloodwaters.

n Development

infloodwaysshallbeprohibited,unlessengineeringanalysesshowthattherewillbeno

increasesinfloodlevels.

GeneralPerformanceRequirements

TheNFIPsbroadperformancerequirementsfornewbuildingsproposedforfloodhazardareasandthe

substantialimprovementof existingfloodpronebuildingsarelistedbelow:

n Buildings

shallbedesignedandadequatelyanchoredtopreventflotation,collapse,orlateralmovement

resultingfromhydrodynamicandhydrostaticloads,includingtheeffectsof buoyancy.

n Building

materialsusedbelowthedesignfloodelevationshallberesistanttoflooddamage.

n Buildings

shallbeconstructedbymethodsandpracticesthatminimizeflooddamageprimarilyby

elevatingtoorabovetheBFE,orbyspeciallydesignedandcertifiedfloodproofingmeasures.

Note

In addition to the floodplain 

management requirements 

discussed in this guide, 

NFIP regulations include 

requirements specific to 

floodplains along rivers and 

streams. Because this guide 

focuses on the construction 

of residential buildings in 

coastal areas, it does not 

provide significant detail on 

these additional requirements. 

For more information about 

these requirements, see 

FEMA 259, Engineering 

Principles and Practices 

for Retrofitting Floodprone 

Buildings, 2001 Edition.
FEDERAL EMERGENCY MANAGEMENT AGENCY 3-5

InvestIgatIng RegulatoRy RequIRements 3

n Buildings

shallbeconstructedwithelectrical,heating,ventilation,plumbing,andairconditioning

equipmentandotherservicefacilitiesthataredesignedand/orlocatedsoastopreventwaterfrom

enteringoraccumulatingwithinthecomponents.

n If 

FEMAhasnotprovidedBFEdataontheFIRM,thecommunitymustobtain,review,andreasonably

utilizeanyBFEdataavailablefromaFederal,aState,orothersourcesforthepurposeof regulating

constructioninSFHAs.

SubdivisionsandOtherNewDevelopmentintheSFHA

n All

proposalsforsubdivisionsandothernewdevelopmentsgreaterthan50lotsor5acres(whicheveris

less)inanSFHAforwhichnoBFEsareshownontheeffectiveFIRMmustbeaccompaniedby100-

yearfloodelevationdata.

n All

proposalsforsubdivisionsandothernewdevelopmentinthe

SFHAmustbeconsistentwiththeneedtominimizeflooddamage

withinthefloodpronearea.

n All

publicutilitiesandfacilities(suchassewer,gas,electrical,and

watersystemsforsuchsubdivisionsandothernewdevelopments)

mustbelocatedandconstructedtominimizeoreliminateflood

damage.

n Adequate

drainagemustbeprovidedforallsuchsubdivisionsandnewdevelopmentsinordertoreduce

exposuretofloodhazards.

NewandReplacementWaterSupplySystemsintheSFHA

n New

andreplacementwatersupplysystemswithintheSFHAmustbedesignedtominimizeoreliminate

infiltrationof floodwaters.

NewandReplacementSanitarySewageSystemsintheSFHA

n New

andreplacementsanitarysewagesystemsintheSFHAmustbedesignedtominimizeoreliminate

infiltrationof floodwatersintothesystemsanddischargesfromthesystemsintofloodwaters.

n Onsite

wastedisposalsystemsmustbelocatedtoavoidimpairmenttothemorcontaminationfrom

themduringflooding.

3.1.3.1 Minimum Requirements for Buildings in V Zones

Theminimumrequirementsenforcedbyparticipatingcommunitiesregardingnewlyconstructed

buildings,substantiallydamagedbuildings,andsubstantiallyimprovedbuildingsinzonesVE,V1Ð V30,

andVpertaintothesitingof thebuilding,theelevationof thelowestfloorinrelationtotheBFE,the

foundationdesign,enclosuresbelowtheBFE,andalterationsof sanddunesandmangrovestands(see44

CFRPart60.3(d)).

Note

For more information about 

opening requirements for the 

walls of enclosures below 

the lowest floors of buildings 

in A Zones, see FEMA 

NFIP Technical Bulletin 1: 

Openings in Foundation Walls 

and Walls of Enclosures.
3-6 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

Siting

Allnewlyconstructedbuildingsmustbelocatedlandwardof thereachof meanhightide(i.e.,themean

highwaterline).Inaddition,human-causedalterationsof sanddunesormangrovestandsareprohibitedif 

thosealterationswouldincreasepotentialflooddamage.Removingsandorvegetationfrom(orotherwise

altering)asandduneorremovingmangrovesmayincreasethepotentialof flooddamage.Therefore,

suchactionsmustnotbecarriedoutwithoutthepriorapprovalof alocalofficial.

BuildingElevation

Allnewlyconstructed,substantiallydamaged,andsubstantiallyimprovedbuildingsmustbeelevated

onopenfoundationsusingpilings,posts,piers,orcolumnssothatthebottomof thelowesthorizontal

structuralmemberof thelowestfloor(excludingtheverticalfoundationmembers)isatorabovetheBFE

(seeFigure3-1).

FoundationDesign

Thefoundationsforallnewlyconstructed,substantiallydamaged,andsubstantiallyimprovedbuildings

(aswellasthebuildingsattachedtothefoundations),mustbeanchoredtoresistflotation,collapse,

andlateralmovementduetotheeffectsof windandwaterloadsactingsimultaneouslyonallbuilding

components.Aregisteredengineerorarchitectmustdeveloporreviewthestructuraldesign,construction

specifications,andplansforconstructionandmustcertifythatthedesignandmethodsof construction

tobeusedareinaccordancewithacceptedstandardsof practiceformeetingthebuildingelevationand

foundationdesignstandardsdescribedabove.Inaddition,erosioncontrolstructuresandotherstructures

(suchasbulkheads,seawalls,andretainingwalls)maynotbeattachedtothebuildingoritsfoundation.

Exceeding NFIP Elevation Requirements in Costal A Zones and V Zones

100-Year

Stillwater

Elevation

100-Year

Wave Crest

Elevation (BFE)

Toward Flood Source

Freeboard

Bottom of 

Lowest Horizontal

Structural Member

Figure 3-1.

MINIMUM NFIP V ZONE REQUIREMENTS: In V Zones, 

buildings must be elevated 

on an open foundation (e.g., 

pilings, posts, piers, or columns) so that the bottom of 

the lowest horizontal structural 

member is located at or above 

the BFE. (Source: FEMA 55) 
FEDERAL EMERGENCY MANAGEMENT AGENCY 3-7

InvestIgatIng RegulatoRy RequIRements 3

Fillmaynotbeusedforthestructuralsupportof anybuildingwithinzonesVE,V1Ð V30,andV.Fill

maybeusedinVZonesforminorlandscapingandsitedrainagepurposesprovidedthatthefilldoesnot

interferewiththefreepassageof floodwatersanddebrisunderneaththebuildingorcausedamagesin

theflowdirectionduringcoastalstormssuchthatfloodwaterswillcauseadditionaldamagestobuildings

onthesiteortoanyadjacentbuildings.

SpaceBelowtheBFE

Thespacebelowallnewlyconstructed,substantiallydamaged,and

substantiallyimprovedbuildingsmusteitherbefreeof obstructionsor

enclosedonlybynon-supportingbreakawaywalls,openlatticework,

orinsectscreeningintendedtocollapseunderwaterloadswithout

causingcollapse,displacement,orotherstructuraldamagetothe

elevatedportionof thebuildingorthesupportingfoundationsystem.

Further,specificNFIPrequirementsareinplaceregardingpermitted

usesbelowtheBFEandtheuseof flood-damage-resistantmaterials

belowtheBFE.TheenclosedareabelowtheBFEcanbeusedfor

parking,buildingaccess,orstoragepurposes,andanymechanicalor

utilityequipmentmustremainprotectedorbeelevatedtotheBFE.

CurrentNFIPregulatoryrequirementsforbreakawaywallsareset

forthat44CFRPart60.3(e)(5).Theregulationsspecifyadesign

safe-loadingresistanceforbreakawaywallsof notlessthan10lb/

ft2

andnotmorethan20lb/ft2.Regulationsalsoprovideforthe

useof alternativedesignsthatdonotmeetthespecifiedloading

requirements.Generally,theuseof breakawaywallsbuiltaccording

tosuchdesignsispermittedif aregisteredprofessionalengineeror

architectcertifiesthatthewallswillcollapseunderawaterloadless

thanthatwhichwouldoccurduringthebasefloodandthattheelevated

portionof thebuildingandsupportingfoundationsystemwillnotbesubjecttocollapse,displacement,

orotherstructuraldamageduetotheeffectsof windandwaterloadsactingsimultaneouslyonall

buildingcomponents.

ResearchconductedforFEMAandtheNationalScienceFoundationbyNorthCarolinaStateUniversity

(NCSU)andOregonStateUniversity(OSU)includingfull-scaletestsof breakawaywallpanels

providesthebasisforprescriptivecriteriarelatedtothedesignandconstructionof alternative-type

breakawaywallpanelsthatdonotmeettherequirementforaloadingresistanceof 10Ð 20lb/ft2

.These

criteriaarepresentedinthe2008FEMANFIPTechnicalBulletin9:DesignandConstructionGuidance

forBreakawayWallsBelowElevatedCoastalBuildings(FIA-TB-9).Thecriteriaaddressbreakawaywall

constructionmaterials(includingwoodframing,light-gaugesteelframing,andmasonry);attachment

of thewallstofloorsandfoundationmembers;utilitylines;wallcoverings(suchasinteriorandexterior

sheathing,siding,andstucco);andotherdesignandconstructionissues.Thebulletinalsodescribesthe

resultsof theNCSU/OSUtests,whicharedescribedingreaterdetailinBehaviororBreakawayWalls

SubjectedtoWaveForces:AnalyticalandExperimentalStudies(Tungetal.,1999).

Note

Although NFIP regulations 

permit below-BFE enclosures 

that meet the criteria presented 

here, many communities may 

have adopted ordinances that 

prohibit all such enclosures 

or that establish more 

stringent criteria, such as an 

enclosure size limitation.

Note

For more information about 

enclosures, the use of space 

below elevated buildings, 

and breakaway walls, see 

FEMA 499, Home Builder’s 

Guide to Coastal Construction 

Technical Fact Sheet Series.
3-8 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

BuildingElevationinZoneA

FIRMsdonotpresentBFEsinSFHAsdesignatedasZoneA(i.e.,unnumberedAZones).Thelowest

floorsof buildingsinZoneAmustbeelevatedtoorabovetheBFEwheneverBFEdataisavailablefrom

othersources.If noBFEdataisavailable,communitiesmustensurethatthebuildingisconstructedwith

methodsandpracticesthatminimizeflooddamage.If aclosedfoundationisused,floodopeningsmust

bepresentinthefoundationwallsinordertoaccountforhydrostaticpressure.

Note: A Pile or Column Foundation may be best.

Design Stillwater Elevation 

(Above 100-Year Stillwater)

Openings for 

Floodwaters

Design Stillwater

Flood Depth

Design Wave

Crest Elevation

Toward Ocean

Top of

Lowest Floor

Crawlspace 

Foundation

Figure 3-2.

MINIMUM NFIP A ZONE 

REQUIREMENTS:

The lowest floors of buildings in 

zones AE, A1–A30, and A must be 

positioned at or above the BFE. 

Foundation walls below the BFE 

must be equipped with openings 

that allow the automatic entry of 

floodwaters so that interior and 

exterior hydrostatic pressures can 

equalize. (Source: FEMA 55)

3.1.3.2 Minimum Requirements for Buildings in A Zones 

Inadditiontothegeneralrequirementsstatedabove,thefollowingminimumrequirementsarespecificto

buildingsandstructureslocatedinzonesAE,A1Ð A30,AO,andA.Thediscussionbelowaddresseshow

eachof therequirementsisdefinedaccordingtothefloodzone.

n The

elevationof thetopof thelowestfloor(i.e.,FinishedFloorElevation(FFE)),includingfinished

basements,inrelationtotheBFEorthedepthof the100-year-floodevent(FFEmustbeator

aboveBFE).

n Enclosed

areasbelowthelowestfloor.(Notethattheserequirementsarethesameforcoastalandnoncoastal

AZones.)

BuildingElevationinZonesAEandA1-A30

Thetopof thelowestfloor(includingthebasementfloor)of allnewlyconstructed,substantiallydamaged,

andsubstantiallyimprovedbuildingsmustbepositionedatorabovetheBFE(seeFigure3-2).If aclosed

foundationisused,floodopeningsmustbepresenttoaccountforhydrostaticpressure.
FEDERAL EMERGENCY MANAGEMENT AGENCY 3-9

InvestIgatIng RegulatoRy RequIRements 3

BuildingElevationinZoneAO

ZoneAOdesignatesareaswherefloodingischaracterizedbyshallowdepths(averaging1to3feet)and/

orunpredictableflowpaths.InZoneAO,thetopof thelowestfloor(includingthebasementfloor)of 

allnewlyconstructed,substantiallydamaged,andsubstantiallyimprovedbuildingsmustbeabovethe

highestgradeadjacenttothebuildingbyatleastthedepthof floodinginfeetshownontheFIRM.For

example,if theflooddepthshownontheFIRMis3feet,thetopof thelowestfloormustbepositioned

atleast3feetabovethehighestgradeadjacenttothebuilding.If nodepthisshownontheFIRM,the

minimumrequiredheightabovethehighestadjacentgradeis2feet.If aclosedfoundationisused,flood

openingsmustbepresentinthefoundationwallstoaccountforhydrostaticpressure.

NotethatareasadjacenttoVZones(suchasbehindbulkheadsoronthebacksidesof dunes)aresometimes

designatedasZoneAO.Forsuchareas,thisguideencouragestheuseof openfoundationsasrequired

inVZones(seeSubsection3.2.4.3of thisguide)forZoneAO.

EnclosuresBelowtheLowestFloorinZonesAE,A1Ð A30,AO,andA

Enclosedspacebelowthelowestfloorsof newlyconstructed,substantiallydamaged,andsubstantially

improvedbuildingsmaybeusedonlyforvehicleparking,buildingaccess,orstoragepurposes.The

wallsof suchareasmustbeequippedwithopeningsdesignedtoallowtheautomaticentryandexitof 

floodwaterssothatinteriorandexteriorhydrostaticpressureswillequalizeduringflooding.Designsfor

openingsmusteithermeetorexceedthefollowingminimumcriteria:

1.Aminimumof twoopeningswithatotalnetareaof notlessthan1squareinchforevery1squarefoot

of enclosedareasubjecttofloodingmustbeprovided.

2.Thebottomsof allopeningsmustbenohigherthan1footabovegrade.

3.Theopeningsmaybeequippedwithscreens,louvers,valves,orothercoveringsordevicesÐ provided

thattheypermittheautomaticentryandexitof floodwaters.

AnalternativetomeetingCriterion1aboveistoprovideacertificationbyaregisteredengineeror

architectthatstatesthattheopeningsaredesignedtoautomaticallyequalizehydrostaticforcesonexterior

wallsbyallowingtheentryandexitof floodwaters.Evenif suchacertificationisprovided,however,the

openingsmuststillmeetcriteria2and3.

3.1.3.3 Recommendations for Coastal A Zones and V Zones 

TheNFIPregulationscurrentlydonotdifferentiatebetweencoastalandnon-coastalAZones.Because

CoastalAZonesmaybesubjecttothetypesof hazardspresentinVZones(suchaswaveeffects,velocity

flows,erosion,scour,andhighwinds),thisguiderecommendsthatbuildingsinCoastalAZonesmeet

theNFIPregulatoryrequirementsforVZonebuildings(i.e.,theperformancerequirementsconcerning

resistancetoflotation,collapse,andlateralmovement,aswellastheprescriptiverequirementsfor

elevation,foundationtype,engineeringcertificationof designandconstruction,enclosuresbelowthe

BFE,andtheuseof structuralfill).
3-10 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

Toprovideagreaterlevelof protectionagainstthehazardstypicalto

CoastalAZonesandVZones,thisguiderecommendsthefollowing

guidanceasgoodpracticeforthesiting,design,andconstructionof 

buildingswithinthosezones:

n The

buildingshouldbelocatedlandwardof boththelong-term

erosionsetbackandthelimitof 100-yearfloodeventerosion,rather

thansimplylandwardof thereachof meanhightide.

n The

bottomof thelowesthorizontalstructuralmembershouldbeelevatedaboveÐ ratherthantoÐ the

BFE(i.e.,freeboardshouldbeprovided;seeFigure3-3).

n Open

latticeworkorscreeningshouldbeusedinlieuof breakawaywallsinthespacebelowtheelevated

buildingor,ataminimum,theuseof solidbreakawaywallconstructionshouldbeminimized.

n In

VZones,thelowesthorizontalstructuralmembersshouldbeorientedperpendicularlytothe

expectedwavecrest.

Toward Flood Source

Toward Flood Source

Bottom of

Lowest

Horizontal

Structural

Member

Bottom of

Lowest

Horizontal

Structural

Member

100-Year

Wave Crest

Elevation

(= BFE)

100-Year

Wave Crest

Elevation

(= BFE)

Wave Trough

DFE

a. Minimum NFIP Elevation Requirement in Coastal A Zones and V Zones

b. Exceeding NFIP Elevation Requirement in Coastal A Zones and V Zones

Figure 3-3.

RECOMMENDED ELEVATION FOR 

BUILDINGS IN COASTAL A ZONES AND 

V ZONES: The bottom of the lowest 

horizontal structural member must 

be positioned above the BFE (rather 

than elevated to the BFE, as shown 

in Figure 3-1). The additional amount 

of elevation above the BFE is 

referred to as “freeboard.” In V 

Zones, the lowest horizontal structural members should be perpendicular to the expected wave crest. 

(Source: FEMA 55)

Note

The term “Coastal A” refers 

to the area within the A Zone 

where breaking waves are 

between 3 feet and 1.5 feet 

high. These areas are not 

specifically delineated on FIRMs.
FEDERAL EMERGENCY MANAGEMENT AGENCY 3-11

InvestIgatIng RegulatoRy RequIRements 3

3.2 Building Codes and Standards

Thepurposeof abuildingcodeistoestablishtheminimumacceptable

designandconstructionrequirementsnecessaryforprotectingthe

publichealth,safety,andwelfarewithinthebuiltenvironment.

Allbuildingcodesandstandardsaredevelopedthroughapublic

consensusprocess.Buildingcodesapplyprimarilytonewconstruction,butmayalsoapplytoexisting

buildingsthatarebeingrebuilt,retrofitted,orrenovated.Codesmayalsoapplywhenabuildingis

undergoingachangeinuse,asdefinedbythecode.Thebuildingcodespecifiestheapplicableclimatic

andgeographicdesigncriteria(includingrainandsnowloads,windspeed,seismicdesigncategory,frost

depth,termitesusceptibility,floodhazards,airfreezingindex,andmeanannualtemperature).

Themostwidelyadoptedmodelcodesaredevelopedbythe

InternationalCodeCouncil(http://www.iccsafe.org).Asof mid

2008,therehasbeenatleastonecommunityinall50statesthat

hasadoptedatleastoneormoreof theI-Codes(includingtheIBC,

IRC,InternationalExistingBuildingCode,andaseriesof codesfor

mechanical,plumbing,fuelgas,andonsitesewageinstallations).This

guidereferencesthe2006editionsof theIBCandIRCalongwith

ASCE7-05andASCE24-05asthoughtheyhavebeenadoptedin

everyjurisdiction.If thesecodeshavenotbeenadoptedinthereaders

jurisdictionwithoutmodification(suchaswithanIBC-basedcode

orwithlocal/stateamendments),therequirementssetforthheremay

beconsideredguidance.

Duringthedevelopmentof theI-Codes,FEMAwasconsultedto

ensurethatthedirectiongiveninthecodesremainsconsistentwith

theminimumrequirementsof theNFIP.Since2000,theI-Codes

haveincludedprovisionsforbuildingsinfloodhazardareas,andthe

2003and2006editionshavebeendeemedbyFEMAtobeconsistentwiththeNFIP.

TheIBCisaperformancecodethatgenerallyrequiresbuildingsandstructurestobeindividuallydesigned

tomeettherequirementsof thecodeandvariousreferencedstandards.Twoimportantstandards

referencedÐ (1)ASCE7-05outliningloadingcriteriaforwind,flood,andenvironmentalloadsand(2)

ASCE24-05Ð includeprovisionspertainingtofloodhazards.Thesestandardsarebrieflydescribedin

Sections3.2.2.1through3.2.3.

TheIRCaddressesrelevantdesigncriteria(loads)inamoreprescriptiveapproachsothatsomeone-and

two-familyhomescanbebuiltwithoutindividualdesignspreparedbyarchitectsandengineers(withthe

exceptionof homesinAandVZones).HomesmaybedesignedandconstructedtotheIRCcriteria,

butgenerallyaprescriptiveapproachtodesignisusedforinlandconstruction.DuetotheIRCnotbeing

prescriptiveaboutflooddesign,coastalconstructionrequirementstypicallyleadtoindividualdesignsof 

residentialstructures.

Note

Applicable climatic and 

geographic design criteria are 

found in IRC Table 301.2(1).

Note

ASCE 7-05 outlines methods 

to determine design loads 

and load combinations in 

flood hazard areas (including 

hydrostatic loads, hydrodynamic 

loads, wave loads, and debris 

impact loads). To compute the 

loads and load combinations, 

the designer must identify 

site-specific characteristics 

(including flood depths, 

velocities, waves, and the 

likelihood that debris impacts 

need to be considered).

ASCE 24-05 addresses design 

requirements for buildings in 

Coastal High Hazard Areas. 
3-12 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

Althoughnotspecificallycoveredinthisguide,oneothernotablebuildingcodeadoptedinsome

jurisdictionsisNFPA5000,BuildingConstructionandSafetyCode,developedbytheNationalFireProtection

Association.Thiscodeincludesprovisionsforbuildingsinfloodhazardareas.TheNFPAalsodevelops

standards,includingNFPA225,ModelManufacturedHomeInstallationStandard,thefirstsuchstandardto

includeprovisionsformanufacturedhomeinstallationwithinfloodhazardareas.Thisstandardprovides

someguidanceonappropriatemeasuresrequiredformanufacturedhomes.

3.2.1 Flood and Wind Requirements in the IBC and IRC

TheIBCaddressesfloodloadsandflood-resistantconstruction

primarilyinSection1612(FloodLoads),whichreferstotheconsensus

standardsASCE7-05(inChapter5)andASCE24-05.Similarly,wind

loadsandwind-resistantconstructionareaddressedinSection1609

(WindLoads)of theIBC.TheIBCstatesthatwindloadsshouldbe

calculatedasindicatedinChapter6of ASCE7-05.Thecodethen

definesprescriptivemethodsfordesigningopenings,louvers,and

roof systems.Floodloads,windloads,andloadcombinationsare

specifiedinSection1605.Thedesignermustidentifythepertinent,site-specificcharacteristicsandthen

useASCE7-05todeterminethespecificloadsandloadcombinations.TheIBC,ineffect,issimilarto

alocalfloodplainordinancethatrequiresdeterminationof theenvironmentalconditions(e.g.,mapped

floodhazardarea,BFE/depthof water)andthenspecifiescertainconditionsthatmustbemetduring

designandconstruction.Thebodyof theIBC(togetherwithAppendixG,if specificallyadoptedbythe

AHJ)addressesallof thekeybuildinganddevelopmentrequirementsof theNFIP.If theAHJchooses

nottoadopttheI-Code,theapplicablecodeshouldcomplywithminimumNFIPrequirements.

TheIRCisaprescriptivecodethatgenerallyprovidesaprescriptivedesignapproachthatsimplifiesthe

designprocessand,asaresult,doesnotalwaysleadtoindividual

designsforresidentialbuildings.TheIBCcanbeusedif thebuilding

doesnotmeettheguidancedevelopedfortheIRC.However,toensure

consistencywiththeNFIPincoastalhigh-hazardareas(VZones),

theIRCrequiressubmissionof documentationbyaregistereddesign

professionalstatingthatthedesignandmethodsof constructionto

beusedmeetapplicablerequirements.TheIRCappliestoone-and

two-familydwellingsandtosometownhouses.InNFIPterminology,

theIRCisusedforresidentialstructures.

TheIRCaddressesflood-resistantconstructionprimarilyinSectionR324(Flood-ResistantConstruction,

renumberedfromR323inpreviousversions),althoughprovisionsformechanicalandplumbing

installationsareincludedinpertinentsectionsof thecode.SectionR301(DesignCriteria)of theIRC

addressesthelimitationsof theprescriptiveaspectsof thecodebaseduponbasicwindspeedrequirements

andstipulatesthatif thewindspeedrequirementsexceedthoseintheprescriptiveguidance,thestructure

shouldbedesignedinaccordancewithoneof fivecodesorstandards(seethelistonthefollowingpage).

SectionR301.2.1.1shouldbeconsultedtoverifythattheapplicable/supplementalcodeordesign

guidanceisbeingused.

Note

A crosswalk of the NFIP regulations and the IBC and IRC provisions is found in the publication 

Reducing Flood Losses through 

the International Code Series: 

Meeting the Requirements of the 

NFIP (published by the ICC) and 

in Table 3-1, which is located 

at the end of this chapter.

Note

Design Flood Elevation (DFE) 

– At a minimum, the Base Flood 

Elevation (i.e., elevation of the 

100-year flood event). However, 

the DFE could be higher due 

to freeboard or additional 

elevation mandated by the 

authority having jurisdiction.
FEDERAL EMERGENCY MANAGEMENT AGENCY 3-13

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n American

Forest&PaperAssociation,WoodFrameConstructionManualforOne-andTwo-FamilyDwellings

(WFCM)

n Southern

BuildingCodeCongressInternational,StandardforHurricane-ResistantResidentialConstruction

(SSTD10)

n ASCE/SEI

7-05,MinimumDesignLoadsforBuildingsandOtherStructures

n American

IronandSteelInstitute,StandardforCold-FormedSteelFraming:PrescriptiveMethodforOne-and

Two-FamilyDwellings(COFS/PM)withsupplementtoStandardforCold-FormedSteelFramingÐ

PrescriptiveMethodforOne-andTwo-FamilyDwellings

n Concrete

constructionshallbedesignedinaccordancewiththeprovisionsof theIRC.

TheIRCdoesnotspecificallyrefertoASCE7-05orASCE24-05forfloodloads.However,

SectionR324.3.6doesrequirearegistereddesignprofessionaltoprepareandsealtheconstruction

documents,thusrequiringthedesignprofessionaltouseASCE7-05andASCE24-05when

designingflood-resistantstructures.

3.2.1.1 Minimum Flood Requirements of the Building Codes

BuildingsconstructedinAandVZonesmustcomplywithspecific

provisionsof theIBCortheIRC,if theyareadopted.Thesummary

belowisanoverviewof themostsignificantrequirements,butitis

notacompletelistingof thecodesandshouldnotbereliedupon

forensuringfullcompliancewitheithertheIBCortheIRC.The

requirementswithinthecodesshouldbeevaluatedduringtheplan

reviewprocessbeforeissuanceof thebuildingpermit.Thepermit

processisdiscussedindetailinChapter4.

TherequirementsoutlinedinIRCSectionR324aresummarizedbelow:

1.Allstructuralsystemsmustbedesignedtoresistflotation,collapse,

orpermanentlateralmovementduetoloadsandstressesfrom

flooding.

2.Allstructurespronetofloodingshallbedesignedtominimize

flooding.

3.AllstructuresshallbeelevatedforcompliancewiththeDFE,asestablishedbylocallyadoptedordinances

andshallbeat(ataminimum)the100-yearfloodelevation.Alicensedarchitect,engineer,orland

surveyormustdetermineandconfirmthatthefloorlevelconformstothatparticularcommunitys

DFE.AllfloorlevelsmustbeestablishedatorabovetheBFEsindicatedontheFIRM.

4.AllmechanicalandelectricalequipmentandcomponentsshallbeelevatedtotheminimumDFE.

Note

In the terminology of the NFIP, 

the International Building Code 

is used for non-residential 

structures. Note, however, that 

the IBC does apply to some 

types of residential structures, 

such as multi-family dwellings. 

Note

The 2009 IRC will require 1 

foot of freeboard in V Zones 

and Coastal A Zones.
3-14 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

5.Allnewandexistingwatersupplyandsanitarysystemsshallbedesignedtoeliminateorminimizethe

infiltrationof floodwaterintothesystem.

6.AllwoodusedbelowtheDFEsshallbepressure-preservative-treatedorbedecay-resistant.

7.InVZones(orCoastalAbylocaladoption),allenclosedareasbelowtheDFEshallbeusedsolely

fortheparkingof vehicles,buildingaccess,andstorage.Inaddition,theenclosuresshallbemade

compliantwiththeprovisionsof thecodetoallowfloodwatermovement.

8.Allfoundationsshallbedesignedtocomplywithallprovisionsof thecodes.

3.2.1.2 Minimum Wind Requirements of the Building Code

Buildingsafetydependsuponmorethantheadoptedcodesandthestandardsthattheyreference.While

building-codeeffectivenessdependspartlyonthepresenceof aneffectivebuildingdepartmentwithinthat

community,truebuildingsafetyismostlikelyachievedwhenbuildingsareproperlydesignedbytrained

professionals,whohavetheresourcesandongoingsupporttheyneedtostayapprisedof advancements

inbuildingsafety.

Aneffectivebuildingsafetysystemprovidesuniforminterpretationsof thecode,productevaluations,and

professionaldevelopmentandcertificationforinspectorsandplanreviewers.Localbuildingdepartments

playakeyroleinensuringthatbuildingsaredesignedandconstructedinaccordancewithapplicable

buildingcodes.

Buildingcodes,however,arenotall-inclusive.Omissionsorconflictswithotherrules,ordinances,or

legislationmayexist.Generallimitationstowindprovisionsinthebuildingcodesincludethefollowing:

n Because

codesareadoptedandenforcedatthelocalorstatelevel,theauthorityhavingjurisdiction

hasthepowertoeliminateormodifywind-relatedprovisionsof amodelcode,ortowriteitsowncode

instead.Injurisdictionsforwhichwind-relatedprovisionsof thecurrentmodelcodearenotadopted

andenforced,buildingsandcriticalfacilitiesaremoresusceptibletowinddamage.Inaddition,atime

lagmayexistbetweenthetimeamodelcodeisupdatedandthetimeitisimplementedbyajurisdiction.

Buildingsdesignedtotheminimumrequirementsof anoutdatedcodeare,therefore,nottaking

advantageof thelatestindustryknowledge.Thesebuildingsarepronetopoorerwindperformance,as

comparedtobuildingsdesignedaccordingtocurrentmodelcodes.

n Adopting

thecurrentmodelcodealonedoesnotensuregoodwindperformance.Toachievegoodwind

performance(inadditiontogooddesign),theconstructionof thebuildingitself mustbeeffectively

executedandthebuildingmustbeadequatelymaintainedandrepaired.

The2006editionsof theIBCandIRCareregardedaseffectivecodes,whentheyarecarefullyfollowed

andtheirrulesproperlyenforced.Neitherthe2006editionsof theIBCortheIRCaccountforthewind

loadsexertedbytornadoes.Theseloadsaregenerallyconsideredtobetooexcessiveforpracticaldesign

of entirebuildings.Thecodesfocusoncreatingstructuresthatwillsustainminimaldamagewhenexposed

tothedesignhazard.Thecodesaredesignedtoprotectstructures;however,itisimportanttonotethat

thecodesarenotintendedtocreatestormshelters.(Occupantsshouldseekrefugeinanappropriate

shelterorFEMAsaferoomintheeventof astorm.)
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The2000,2003,and2006editionsof theIBCrelyonseveralreferencedstandardsandtestmethods

developedorupdatedduringthe1990s.Priortoadoption,mostof thesestandardsandtestmethods

hadnotbeenvalidatedbyactualbuildingperformanceduringdesign-levelwindevents.Thehurricanes

of 2004and2005providedanopportunitytoevaluatetheactualperformanceof buildingsdesigned

andconstructedtotheminimumprovisionsof theIBC.Buildingperformanceevaluationsconducted

byFEMArevealedtheneedforfurtherenhancements.Alimitationof the2006editionsof theIBC

andIRCinvolvessomeof thetestmethodsusedtoassesswindandthewind-drivenrainresistanceof 

building-envelopecomponents.However,beforethiscodelimitationcanbeovercome,researchmustbe

conductedandnewtestmethodsdeveloped.

Theselimitationsshouldnotbeseenasinadequaciesinthecodes,butratherasissuesaboutwhich

buildingofficialsshouldremainaware.OverwhelmingevidencesuggeststhatstructuresbuilttoIBCand

IRCstandardsperformsignificantlybetterduringstormeventsthanbuildingsnotconstructedtocode.

Inmanycases,structuresbuilttoIBCandIRCstandardsweretheonlyonestosurvivestormloadsin

impactedareas.

3.2.1.3 Evolution of Wind Requirements in the Building Codes and Standards

Recognitionof increasedupliftloadsattheroof perimeterand

corners.Priortothe1982editionsof theStandardBuildingCode

andtheUniformBuildingCode,andthe1987editionof theNational

BuildingCode,thesemodelcodesdidnotaccountfortheincreased

upliftattheroof perimeterandcorners.Therefore,buildingsdesigned

inaccordancewithearliereditionsof thesecodesareverysusceptible

tothelossof theroof coveringand/orroof deckingduringhighwind

events.

Adoptionof ASCE7fordesignwindloads:AlthoughtheStandard

BuildingCode,theUniformBuildingCode,andtheNational

BuildingCodepermittedtheuseof ASCE7,the2000editionof 

theIBCwasthefirstmodelcodetorequireASCE7fordetermining

winddesignloads.TheIRCalsorecommendstheuseof ASCE7

forwinddesignorothermethods,butprovidesalternativetablesfor

prescriptivedesignpressuresforqualifiedbuildings.

Roof coverings:Severalperformanceandprescriptiverequirementspertainingtothewindresistanceof 

roof coveringshavebeenincorporatedintothemodelcodes.Poorperformanceof roof coveringswas

widespreadduringhurricanesHugo(1989)andAndrew(1992).Priortothe1991editionsof theStandard

BuildingCodeandtheUniformBuildingCode,andthe1990editionof theNationalBuildingCode,

thesemodelcodesdidnotdirectlyaddressroof coveringwindloadsandtestmethodsfordetermining

upliftresistance.Mostof theseadditionalprovisionswereaddedfollowingHurricaneAndrew.Following

thesestorms,BuildingPerformanceAssessmentTeams(BPAT)weredispatchedtoevaluateconstruction

techniquesusedonvariousbuildingsandgatherinformationbaseduponthedamages.TheseBPATs

(nowcalledMitigationAssessmentTeams[MAT])werecomprisedof technicalexpertsfromFEMA,

codeexperts,andconsultantsfrompublicandprivateentities.TheBPATsandMATshavemade

recommendationsonimprovingbuildingperformanceandinfluencedfuturecodesinthisandotherareas

of study.Changestothebuildingcodesbasedupontheserecommendationscontinuetobemadethrough

Note

ASCE 7-05 requires the 

protection of glazed openings in 

windborne debris areas within 

hurricane-prone regions. Glazing 

protection can be an impactresistant glazing protection 

(such as laminated glass or 

polycarbonate) or shutters or 

screens tested in accordance 

with ASTM standards specified 

in ASCE 7-05. The windborne 

debris-protection criteria 

were developed to minimize 

property damage and to improve 

building performance. (The 

criteria were not developed 

for occupant protection.) 
3-16 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

the2006editionof theIBC(suchas,Section1504.8whichaddedaprovisionprohibitingaggregate

roof surfacesinhurricane-proneregions)andalsofutureeditionswhicharecurrentlyintheconsensus

developmentprocess.

Glazingprotection:The2000editionof theIBCwasthefirstmodelcodetoaddresswindbornedebris

requirementsforglazinginbuildingslocatedinhurricane-proneregions(viareferencetothe1998edition

of ASCE7).The1995editionof ASCE7wasthefirsteditionof thatstandardtoaddresswindborne

debrisrequirements.

Parapetsandrooftopequipment:The2003editionof theIBCwasthefirstmodelcodetoaddresswind

loadsonparapetsandrooftopequipment(viareferencetothe2002editionof ASCE7,whichwasthe

firsteditionof ASCE7toaddresstheseelements).

3.2.2 ASCE 7 Requirements

TheASCEdevelopsandmaintainstheconsensusstandardforloaddeterminationonbuildingsand

structures:ASCE7-05.Thisstandardspecifiestheloadsandloadcombinationstobeusedindesignand

isincorporatedbyreferencesinthe2006editionsof boththeIBCandtheIRC.Thisstandardisthebasis

forloadingsusedinmanyof theprescriptivemethodsoutlinedintheIRC.Thedesignloadsfornewor

modifiedconstructionconsiderpermanentandtemporaryloads(suchassnowandrainloading),aswell

asloadsfromothermoresignificantnaturalhazards(suchasseismicevents,highwind,andfloodloads).

Forthisguide,flood-andwind-loadrequirementsarediscussedbecausetheyarethemostsignificant

loadconditionswithincoastalareas.Thecommentarysectionsof ASCE7providedetaileddiscussions

of theseandotherloads.

3.2.2.1 Flood Requirements

Coastalareasexperienceseveralfloodloadsthatcanoccursimultaneously.Stormsurge,debrisimpact,

erosion,andscourcancontributetoloadsexertedonabuilding.Thefollowingsectionsof ASCE7

addressfloodloads:

n Section

2:Combinationsof Loads,includingdifferentloadcombinationsforVZonesandCoastalA

Zones.

n Section

5:FloodLoads,whichcovershydrostatic,hydrodynamic,wave,andimpactloads.Loadcriteria

forbreakawaywallsareincluded.

Inrecognitionof thegrowingawarenessthatwaveswithheightsbetween1.5feetand3feethigh(the

cutoff usedtodelineateFEMAsVZone)cancauseconsiderabledamage,ASCE7-05incorporatesthe

conceptof theCoastalAZoneandspecifiesthatdesignersmustdeterminebreakingwaveloadson

structureswithintheseareas.
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3.2.2.2 Wind Requirements

Becauseof theirgeographiclocation,manycoastalcommunitiesaresusceptibletohigh-windevents,

suchashurricanes,tornadoes,andnoreasters.ThewindpressurescalculatedinaccordancewithASCE

7-05areappliedtotributaryareasonthebuilding.Theseloadsresultinforcesthatshouldbeevaluatedat

connectionsandatstressesinstructuralmembers,ortotheMainWindForceResistingSystem(MWFRS).

Forcesarealsocalculatedforwallsheathing,roof panels,windows,anddoorsallof whichisreferred

tocollectivelyasthecomponentsandcladding(C&C).Calculatedwindpressuresarelargelydependant

uponsitelocation,topography,buildingshapeandconfiguration,andbuildingimportance.Figure3-4is

asectionof amapshowingareasalongtheEastCoastof theUnitedStatesthataresubjecttohurricanes.

ASCE7sectionsthatpertaintowindloadsandloadingcombinationsare:

n Section

2:Combinationsof Loads,includingdifferentloadcombinationsforVZonesandCoastalA

Zones.

n Section

6:WindLoads,whichcoversMWFRSandC&C.Adiscussionof windbornedebrisisalso

includedinthissection.

Figure 3-4.

The hurricane-prone regions along the coastline of the United States. This map is based upon ASCE 7-05, Figure 6-1.
3-18 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

3.2.3 ASCE 24 Requirements

ASCEdevelopsandmaintainstheconsensusstandardASCE24-05.Thisstandardspecifiesminimum

requirementsforflood-resistantdesignandconstructionofbuildingsandstructureslocatedinflood

hazardareas,includingfloodwaysandcoastalhigh-hazardareas.Thestandardappliestonew

buildingsandexistingstructuresthatarenotdesignatedashistoricstructuresbutwhichareundergoing

substantialrepairorimprovements.

Basicdesignrequirementsaddressfloodloadsandloadcombinations,elevationofthelowestfloor,

recommendationsabouttheDFE,foundationrequirementsandgeotechnicalconsiderations,useoffill,

andanchoringandconnections.Asafunctionofthetypeoffloodhazardarea,enclosuresmayneed

breakawaywallsormustmeetrequirementsforfloodopenings(eitherprescriptiveorengineered).ASCE

24-05doesnotaddresswindhazardsspecifically,butdoesreferencethefactthatloadcombinationson

structuresshallbeinaccordancewithASCE7-05,whichwouldincludewindloads.

Forbuildingsincoastalhigh-hazardareas,VZonesandCoastalAZones,ASCE24-05includes

specificationsforthedesignofpile,post,pier,column,andshearwallfoundations.Considerabledetail

isspecifiedforpilingsasafunctionofpiletypesandconnections.

ASCE24-05statesthatresidentialstructuresinVZonesandCoastalAZonesarerequiredtohave

openfoundationsandshallhavethelowesthorizontalstructuralmemberofthelowestfloorpositioned

atorabovetheDFE.Theminimumelevationrequirementsarebaseduponthestructuralmembers

orientationtothedirectionofwavesapproaching.Forparallelmembers,therequirementisDFEand

theperpendicularmembersarerequiredtobeBFE+1orDFE(whicheverishigher).

ThefollowingtopicsarealsoaddressedwithinASCE24-05:materials,dryandwetfloodproofing,

utilityinstallations,buildingaccess,andmiscellaneousconstruction(e.g.,decks,porches,patios,

garages,chimneysandfireplaces,pools,andabove-andbelow-groundstoragetanks).Itisimportant

tonotethatsomesectionsofASCE24-05exceedtheminimumrequirementssetforthintheNFIP;

specificallyfreeboardrequirements.AstructuredesignedtoASCE24-05standards,whichinclude

freeboardcriteria,wouldlikelyperformbetterduringadesignevent(byresistingfloodloadsbetter)

thanabuildingnotconstructedtotheminimumNFIPcriteriathatrecommend,butdonotrequire

freeboard.Untilsuchstandardsandapproachesaredirectlyincorporatedintothebuildingcodesor

regulations,withoutoptions,thenthesestandardsandapproachesshouldbeconsideredbestpractices

andnotrequirements.

3.3 Coastal Barrier Resources Act of 1982

TheCoastalBarrierResourcesAct(CBRA)of1982wasenactedtoprotectvulnerablecoastal

barriersfromdevelopment;minimizethelossoflife;reduceexpendituresofFederalrevenues;and

protectfish,wildlife,andothernaturalresources.ThislawestablishedtheCoastalBarrierResources

System(CBRS),whichismanagedbytheDepartmentoftheInteriors(DOI)UnitedStatesFish

andWildlifeService(USFWS).ThelawrestrictsFederalexpendituresandfinancialassistance

thatcouldencouragethedevelopmentofcoastalbarriers.TheCBRAdoesnotprohibitprivately

financeddevelopment;however,itdoesprohibitmostnewFederalfinancialassistance-including

federallybackedfloodinsurance-inlocationswithintheCBRS(alsoreferredtoasCBRAareas).Flood
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insurancemaynotbesoldforbuildingswithintheCBRSthatwere

constructedorsubstantiallyimprovedafterOctober1,1983.The

financialriskofbuildingintheseareasistransferredfromFederal

taxpayersdirectlytothosewhochoosetoresideinorinvestin

theseareas.

CBRSboundariesareshownonaseriesofmapsproducedbyDOI.

Inaddition,FEMAhastransferredCBRSboundariestomany

FIRMssothatinsuranceagentsandunderwritersmaydetermine

eligibilityforfloodinsurancecoverage.Beforeconstructinganew

building,substantiallyimprovinganexistingbuilding,orrepairing

asubstantiallydamagedbuilding,thedesignerorpropertyowner

shouldreviewtheFIRMandconfirmforthebuildingofficialthat

thepropertyisnotwithintheCBRS.Ifthestructureisconsidered

withintheCBRS,thebuildingofficialshouldnotifythedesignerorpropertyownerofanyspecial

ordinancesspecifictostructureswithintheCBRS.InsituationswheretheFIRMdoesnotallow

foradefinitivedetermination,thedesignerorpropertyownershouldconsultlocalofficials.Insome

situations,itmaybenecessarytorequestadeterminationfromUSFWS,baseduponDOImaps.

3.4 Coastal Zone Management Regulations

TheCoastalZoneManagement(CZM)Actof1972encouragestheadoptionofcoastalzonepolicies

bycoastalstatesactinginpartnershipwiththeFederalgovernment.CZMregulationshavebeen

adoptedby34statesandterritories.ForinformationonthestatusofstateandnationalCZM

programs,visittheWebsiteoftheNationalOceanicandAtmosphericAdministration(NOAA)at

http://oceanservice.noaa.gov/topics/coasts/management/.

EachstatesCZMprogramcontainsprovisionsto:

n Protect

naturalresources

n Manage

developmentinhigh-hazardareas

n Manage

developmenttoachievequalitycoastalwaters

n Give

developmentprioritytocoastal-dependentuses

n Have

orderlyprocessesforthesitingofmajorfacilities

n Locate

newcommercialandindustrialdevelopmentin,oradjacentto,existingdevelopedareas

n Provide

publicaccessforrecreation

n Redevelop

urbanwaterfrontsandports,andpreserveandrestorehistoric,cultural,andaesthetic

coastalfeatures

n Simplify

andexpeditegovernmentaldecisionmakingactions

Note

Any building within a Coastal 

Barrier Resources System 

(CBRS) area that is constructed 

or substantially improved after 

October 1, 1983 (or the date 

of designation for areas added 

to the system after 1991) is 

not eligible for federal flood 

insurance or other federal 

financial assistance. The 

same restriction applies to 

substantially damaged buildings 

in a CBRS area that are repaired 

or renovated after those dates. 
3-20 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

n Coordinate

stateandFederalactions

n Give

adequateconsiderationtotheviewsofFederalagencies

n Assure

thatthepublicandlocalgovernmentsareconsultedduringcoastaldecisionmaking

n Comprehensively

planforandmanagelivingmarineresources

Moststatecoastalzoneregulationscontrolconstructionseawardofadefinedboundaryorsetbackline,

suchasaduneorroad.Manystatesregulateorprohibitconstructionseawardofasecondsetbackline,

whichisbaseduponerosion.Somesetbacklinesareupdatedwhenerosionratesareassessed;lines

thatfollowphysicalfeatures(suchasdunelines)arenotfixedandfloatasthephysicalfeatureshifts

overtime.Otherexamplesofstatecoastalregulationsincludetheplacementorprohibitionofshore

protectionstructuresandtheprotectionofdunes.Theserestrictionsshouldbecarefullyconsidered

bystateandlocalregulatoryofficialsbecauseguidanceontheregulationsissite-specifictocoastal

conditionswithinthatarea.

3.5 Use of the NFIP and Code Crosswalk 

Toprovideinformationontheguidanceineachdocumentortoidentifythelocationoftheinformation

withinthedocument,thissectionprovidesausefulcrosswalksummaryofNFIPregulations(aswell

astheIBC,IRC,ASCE24-05,andASCE7-05)foreachcoastalzone.Inmanycases,information

isprovidedaboutwhethertheguidanceisarequirementofthatdocumentorabest-practices

recommendation.ThecrosswalkreferstotheBFE;however,somejurisdictionsmayincludefreeboard,

and,inthesecases,theguidanceshouldbeunderstoodastheDFE.

Table3-1wasdevelopedusingAppendixBandAppendixCofReducingFloodLossesThroughthe

InternationalCodes(ICC/FEMA,2ndEdition,2005)andupdatedtoreflectthe2006versionsofthe

IBCandIRC.Thiscrosswalksummaryisintendedtoprovideguidanceonthelocationsofapplicable

codesections.Itisnotacompletelist,andthelocalofficialshouldbeencouragedtoconsultthat

particularcode.
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3-22 local offIcIals guIde foR coastal constRuctIon

3 InvestIgatIng RegulatoRy RequIRements

NFIP V Zone Coastal A

GENERAL REQUIREMENTS

Design and Construction 60.3(a)(3)(i) New construction and substantial 

improvements to be designed and adequately anchored to 

prevent flotation, collapse, or lateral movement.

Requirement: Building and its foundation must 

be designed, constructed, and anchored to 

prevent flotation, collapse, and lateral movement 

due to simultaneous wind and water load.

Requirement: Building must be designed, 

constructed, and anchored to prevent flotation, 

collapse, and lateral movement resulting from 

hydrodynamic and hydrostatic loads, including 

the effects of buoyancy.

Recommendation: Same as V Zone.

Materials 60.3(a)(3)(ii) New construction and substantial 

improvements to be constructed with materials resistant 

to flood damage.

Requirement: Structural and nonstructural 

building materials at or below the BFE must be 

flood-resistant.

Requirement: Structural and nonstructural 

building materials at or below the BFE must be 

flood resistant.

Siting 60.3(d)(3) Prohibit floodway encroachment unless no 

impact on flood levels is demonstrated.

60.3(e)(3) All new construction shall be landward of mean 

high tide.

60.3(e(7) Alteration of sand dunes and mangrove stands 

that increases

Requirement: All new construction shall be 

landward of mean high tide; alteration of sand 

dunes and mangrove stands that increases the 

potential of flood damage is prohibited.

Recommendation: Site new construction 

landward of the long-term erosion setback and 

landward of the area subject to erosion during the 

100-year coastal flooding event.

Requirement: Encroachments into the SFHA are 

permitted as long as they do not increase the 

BFE by more than 1 foot; encroachments into the 

floodway are prohibited.

Recommendation: Same as V Zone.

FOUNDATION

Structural Fill 60.3(e)(6) Prohibit the use of fill for structural support of 

buildings in V Zones.

Prohibited Allowed, but not recommended; compaction 

required where used; protect against scour and 

erosion.

Solid Foundation Prohibited Allowed, but not recommended.

Open Foundation Required Not required, but recommended.

Lowest Floor Elevation 

(non V Zone)

60.3(c) Require all new and substantially improved 

structures: 

(2) to have the lowest floor elevated to or above the flood 

elevation or, (3) be floodproofed (nonresidential only)

N/A Requirement: Top of floor must be at or above 

BFE Recommendation: Elevate bottom of lowest 

horizontal structural member to or above BFE

Bottom 

Lowest Horizontal 

Structural Member

60.3(e)(4) Require all new and substantially improved 

construction to be elevated on pilings and columns so that: 

(i) bottom of lowest horizontal structural member is at or 

above the flood elevation, (ii) pile or column foundation 

and structure are anchored to resist flotation, collapse, 

and lateral movement due to wind and water loads; 

registered design professional to develop or review the 

design, specifications, and plans and provide certification.

Requirement: Bottom must be at or above the 

BFE.

Allowed below BFE but not recommended.

Recommendation: Same as V Zone.

Orientation of Lowest 

Horizontal Structural 

Member

None No requirement

Recommendation: Orient perpendicular to wave 

crest

No requirement

Freeboard None Not required, but recommended Not required, but recommended

Enclosures 

Below the BFE 

(non V Zones)

60.3(c)(5) Fully enclosed areas below elevated buildings 

are to be: limited in use (parking, access, storage); 

provided with flood openings that meet minimum criteria 

or are designed by a registered design professional.

N/A Allowed, but not recommended; if an area 

is fully enclosed, the enclosure walls must be 

equipped with openings to equalize hydrostatic 

pressure; size, location, and covering of openings 

governed by regulatory requirements.

Recommendation: If enclosure if constructed, 

use breakaway walls, open lattice, or screening 

(as required in V zones).

Enclosures 

Below the BFE 

(V Zones)

60.3(e)(5) Enclosed areas, if any, are to be constructed 

with non-supporting, breakaway walls, lattice, or 

screening intended to collapse under wind and water 

loads; uses limited to parking, building access, or storage.

Prohibited, except for breakaway walls, open 

lattice, and screening.

N/A

Sanitary Sewer 60.3(a)(6) (i) New/replacement sanitary sewage system 

designed to minimize/eliminate infiltration/discharges 

(ii) on-site waste disposal systems located to avoid 

impairment or contamination.

Utilities 60.3(a)(3)(v) Electrical, heating, ventilation, plumbing, and 

air-conditioning equipment and other service facilities to 

be designed and/or located to protect components.

Requirement: Must be designed, located, and 

elevated to prevent floodwaters from entering 

and accumulating in components during flooding.

Requirement: Must be designed, located, and 

elevated to prevent floodwaters from entering 

and accumulating in components during flooding.

CERTIFICATION

Permits 60.3(b)(1) Require permits for all development, including 

placement of manufactured homes.

V Zone Certificate, Breakaway Wall Certificate, 

and Elevation Certificate

Elevation Certificate

MANUFACTURED HOUSING

General 60.3(b)(8) Require installation of MFH using methods to 

minimize flood damage, including anchoring, and to resist 

wind forces.

Table 3-1. Code Crosswalk
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A Zone IBC IRC ASCE 24 and ASCE 7 Other

GENERAL REQUIREMENTS

Requirement: Building must be designed, 

constructed, and anchored to prevent flotation, 

collapse, and lateral movement resulting from 

hydrodynamic and hydrostatic loads, including the 

effects of buoyancy.

Recommendation: Same as V Zone

1605.2.2 (reference ASCE 7)

1605.3.1.2 (reference ASCE 7)

1612.4 (reference ASCE 24)

1612.5.2, 3403.1.1

R301.1

R301.2.4

R323.1

ASCE 24 Sec. 5.6

ASCE 24 Sec. 1.5.1

Requirement: Structural and non-structural 

building materials at or below the BFE must be 

flood resistant.

801.1.3,

1403.5

R324.1.7 ASCE 24 Ch. 5 FEMA TB #2

FEMA TB #8

Requirement: Encroachments into the SFHA are 

permitted as long as they 

do not increase the BFE by more than 1 foot; 

encroachments into the floodway 

are prohibited.

App. G 103.5

App. G 103.6

App. G 103.7

App. G 401.1

App. G 401.2

R301.2.4

R324.3.1

ASCE 24 Sec. 2.3

ASCE 24 Ch. 3

ASCE 24 Sec. 4.3

FEMA EMI IS-9,

FEMA FIA-12

FOUNDATION

Allowed; compaction required where used; protect 

against scour and erosion.

App. G 401.1 R324.3.2 ASCE 24 Sec. 2.4 FEMA TB #5

Allowed R324.2.3 ASCE 24 Sec. 2.5

ASCE 7 Sec. 5.4.4.2

FEMA TB #5

Allowed ASCE 7 Sec. 5.4.4.1

ASCE 24 Sec 4.5.5

FEMA TB #5

Requirement: Top of floor must be at or above 

BFE

1603.1.6

1612.4

R105.3.1.1

R324.2.1

R324.1.4

ASCE 24 Sec. 1.5.2

ASCE 24 Sec. 2.5

ASCE 24 Ch. 5

ASCE 24Ch. 7

FEMA 259

FEMA TB #3

FEMA 348

Allowed below BFE but not recommended.

Recommendation: Same as V Zone

1603.1.6

1612.4

1612.5.2

R324.2.1

R324.3.2

R323.3.5

ASCE 24 Sec. 4.4

ASCE 24 Sec. 2.5

ASCE 24 Ch. 5

FEMA 55,

FEMA TB #8

FEMA TB #5

No requirement ASCE 24 Sec 4.4 No requirement

Not required, but recommended

Allowed, but not recommended; if an area is fully 

enclosed, the enclosure walls must be equipped 

with openings to equalize hydrostatic pressure; 

size, location, and covering of openings governed 

by regulatory requirements.

1203.3.2

1403.5

1612.4

1612.5.1

R324.2.2

R408.7

ASCE 24 Sec. 2.6

ASCE 24 Sec 4.6

FEMA TB #1

NA 1403.5

1403.6

1612.4

1612.5.2

R324.3.4

R324.3.5

ASCE 24Sec. 4.6

ASCE 7 Sec. C5.3.3

FEMA 55

FEMA TB #5,

FEMA TB #9

1403.6

App. G 401.3

R324.1.6 ASCE 24 Sec. 7.3.4 FEMA 348

Requirement: Must be designed, located, and 

elevated to prevent flood waters from entering 

and accumulating in components during flooding.

1403.6

1612.4

App. G 701

R324.1.5

IFGC 301, R G2404

R M1601.3.8

ASCE 24 Ch. 7 FEMA 348,

FEMA TB #4

CERTIFICATION

Elevation Certificate App. G 101.3

App. G 103

App. G 104

R104.2,

R105.3.1.1

App. E

App. J

FEMA EMI IS-9

MANUFACTURED HOUSING

App. G 501 R324.1.8, App. AE101 NA FEMA 85

Table 3-1. Code Crosswalk Continued

FEDERAL EMERGENCY MANAGEMENT AGENCY 4-1

PERMITS AND INSPECTIONS 4

Permits 

and Inspections

4.1 Introduction

T

hischapterdescribesthecoastal-specificbuildingpermitprocess.Inadditiontothischapter,the

Appendixincludesseriesof resourcesandcheckliststhatwereassembledfromprocessescurrently

inusearoundtheUnitedStates.Theseprocessesrepresentsomeof thebestpracticesthathave

successfullyguidedhazard-resistantdesignandconstruction,butthisisnotmeanttoimplythattheyare

theonlymethodsof achievinghazard-resistantconstruction.

Toassistinconductingeffectiveandefficientbuilding-permitapplicationreviews,sampleorganizational

structuresandapermit-processingflowchartareincluded.Themethodsdescribedwillassistthoseworking

towardthedevelopmentof aninitialbuildingdepartmentprogramorthoseattemptingtoimproveupon

anexistingprogram.Examplesof toolsandtechniquesarelistedintheAppendixtothisguide.Noone

exampleismeanttoserveasasinglesolution,norshoulditbeexpectedtodoso.FEMAisawarethat

notwojurisdictionswillhaveidenticalregulatoryresponsibilitiesandthattheimplementationof some

processespresentedmaybetheresponsibilityof oneormoreofficials.

Thenumerous,complex,andpotentiallyconflictingFederal,state,andlocallaws,regulations,and

ordinancesthatimpactthebuildingpermitprocesscanbeoverwhelming.Tosuccessfullyinterpretand

understandthepertinentregulations,thisguidepresentsimportantregulatoryfacts,managementtools,

andorganizationaltechniquestoassistindevelopingormodifyingalocalpermit-processingprogram.

Establishingeffectivemethodsforbuildingapplicationsubmittals,reviews,andapprovalsincoastal

areasiscriticalfordevelopingaconsistent,thorough,andsystematicapproachtotheprocessingof these

requests.Asuccessfulmethodcanbebeneficialbecauseitcan:(1)ensurethateverypermitapplication

isproperlyreviewedandconsidered;and(2)assistinthedevelopmentof arationalandefficientwayto

performreviewsthatpromotethehealth,safety,andwelfareof thepublic.Thekeytohowsmoothlythe

coastaldevelopmentreviewprocessflowsdependsuponhowabuildingdepartmentisorganizedand

howwellitsstaff functions.Communitymembers,homebuilders,andpropertypurchasersmustallrely

upontheprocess.

Adisorganizedsystemcanleadtopoorlysited,designed,orconstructedbuildings.Poorconstruction

typicallyresultsinlossesthatcouldhavebeenprevented.Communityaction(takenthroughabuilding

department)canadvancepreventiveactionbyrigorouslyenforcingbuildingcodesandotherimportant

requirements.Theseactionscansignificantlydecreasethebuildingdamagesresultingfromcoastalstorm

events.Althoughitisimpossibleforpropertyandstructurestobecompletelysparedfromdamages

resultingfromallhigh-windandfloodingevents,proactivestepscansignificantlyreducetheimpactof 

suchdevastatingstorms.
4-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

4 PERMITS AND INSPECTIONS

4.2 Coastal Building Official/ 

Floodplain Administrator’s Responsibilities

Whetherthelocalcoastalcommunityhasappointedabuildingofficialandafloodplainadministrator

ormanager(ortheseroleshavebeencombinedintoone),itisvitaltounderstandtheserolesand

responsibilitiesandtheirrespectiveimportance.AnycommunitythatadoptsaFloodDamagePrevention

Ordinance(FDPO)haslegallyagreedtoregulateallsignificantdevelopmentactivitywithintheSFHA.

Inreturn,propertyownersmaybecomeeligibletoapplyforFederalfloodinsurance,disasterassistance,

andfederallybackedloans.

Theriskof damagetolives,buildings,andstructuresisespeciallyacuteincoastalareas.Tropicalstorms,

noreasters,andhurricanesproducesustainedhighwinds,wind-drivenrains,wavesurges,flooding,and

severeerosion.Becausethesefiercestormeventspoundcoastalareas,coastalbuildingsandstructures

mustbeconstructedsothattheyremainserviceableduringandaftersuchevents.

Coastalconstructionrequiresspecialdesignconsiderationsand,attimes,isbasedonaparticulardesign

event.Buildingfoundationsmustbeconstructedtoresistfloodforces,evenwhenerosionandscour

occur.Acontinuousloadpathmustexistwithinthestructuralsystemtocarryallverticalandlateral

loadsthroughthefoundationandintotheground.Thebuildingenvelope(whichcomprisesallbuilding

surfacesthatseparatetheenclosedfloorspacefromtheelements)mustresistsignificantdamageand

ensuretheleastamountof penetrationbywind,rain,anddebris.Floodwatermustbepreventedfrom

enteringoccupiablebuildingareasbyelevatingthestructuretoaheightgreaterthantheexpectedflood

level.Buildingaccessibilityandusefulnessmustbepreserved.Specialutilityconnectionsmusteither

remainintactorbeeasilyrestored.AnyenclosuresconstructedbelowtheBFEorDFEmustnotdamage

thebuildingsfoundation,utilityconnections,oranyelevatedbuildingassembly(orpartthereof)inthe

eventthoseenclosuresfail.

4.2.1 Enforcement of Regulations

Theprimaryroleof thelocalbuildingofficialandfloodplainadministratoristoenforcelocalregulations.

WithrespecttotheNFIP,thelowestfloor(includingthebasements)of allnewcoastalconstruction,or

allsubstantialimprovementsmadetothatconstruction,mustbelocatedatorabovetheBFE(orDFE,

insomecommunities).Thismeansthatthelowestfloorelevationforallneworsubstantiallyimproved

homesinSFHAswithinthe100-yearfloodplainsmustbeelevatedatorabovethiselevation.

4.2.2 Records Management

Localofficialsareresponsibleforaccuraterecordkeepingandtheretainingof alldevelopmentpermits.

Twodocumentsareusedtorecordthisspecificactivity:(1)theFloodplainDevelopmentPermit(FDP),

and(2)theElevationCertificate(EC)orequivalentelevationdocumentation.Samplesof theseforms

canbefoundintheAppendixtothisguide.ThesedocumentsarehelpfulwhencompletingtheFEMArequired

BiennialReport,whichrecordsstatisticalinformationaboutallfloodhazardareachanges,all

floodplain-developmentactivities,andthenumberof residentsandstructureswithinthefloodplain(see

Section4.2.2.1).TheNFIPrequiresthelocalbuildingofficial(orotherauthorizeddesignee)toretain

copiesof theFDPandrecordsof relevantbuildingelevations.AnapprovedFDPisrequiredforeachof 

thefollowingfloodplain-developmentactivities:
FEDERAL EMERGENCY MANAGEMENT AGENCY 4-3

PERMITS AND INSPECTIONS 4

n Erecting

orenlargingastructure

n Siting

amanufacturedhome

n Mining,

dredging,filling,grading,orexcavatingformajorlandscapingprojects

n Building

orrepairingroadsandbridgesinfloodhazardareas

n Any

human-causedchangesinthefloodplain,includingstorage

Thepermitapplicationform,whichisobtainedfromthebuildingofficial/floodplainadministrator,must

becompletedandsubmittedforreviewandapprovalbeforebeginningtheproposedactivity.ForFDPs,

thelocalfloodplainadministratorreviewsthepermitforcompletenessandensuresthatthedevelopment

activityfullycomplieswithFDPOrequirements.Afterthereview,thepermitiseitherdeniedorapproved.

Acopyof thecompletedpermitis(andmustremain)attachedtothebuildingpermit.

Aspartof theNationalFloodInsuranceActof 1968,bothFEMAandstatesarerequiredtoconduct

CommunityAssistanceVisits(CAV).Duringthesevisits,officialswillreviewacommunityforcompliance

withtheNFIPandwillreviewrecordsaspartof assuringcompliancewiththeprogram.Followingthe

visit,FEMAandthestatewillnoteanycomplianceproblemswiththecommunitysprogramandwork

withthatcommunityinordertoremedythedeficiencies.

4.2.2.1 Biennial Reports to FEMA

FEMAperiodicallysendsBiennialReportformstoNFIP-participatingcommunities.Theseformsare

tobecompletedandreturnedtoFEMA.Communityupdatesof previouslysubmitteddatahelpFEMA

andthestatesplanfortechnicalassistanceandfloodmaps.FEMAisparticularlyinterestedinthenumber

of permitsissuedandthevariancesgranted.Accuraterecordkeepingisessentialforacommunityto

properlycompleteitsBiennialReports.

TheECdocumentstheBFEincomparisontothestructureslowestfloor(orthelowesthorizontal

structuralmemberinVZones).TheECandacopyof thebuildingpermitsshouldbekepttogether.The

ECdocumentsthatthestructureslowestfloorisabovetheBFEandthattheFloodDamagePrevention

Ordinancewasfollowed.

Itisimportantthatthesedocumentsbemaintainedinonefileorcanbeeasilycross-referenced.Additional

datathatisimportanttocaptureorretainincludesacopyof theapplicableFIRMpanel(includingthe

FIRMpanelnumberandeffectivedate)andthedatethebuildingwasconstructed.Thiswillensurea

recordof thecomplianceof thestructureif BFEschangeonfutureFIRMupdates.Thisinformation

shouldalsoincluderequestedvariances(bothacceptedanddenied),notedviolations,andrecordsof 

citationsmadetopropertyownersfornoncompliance.

Inmanyareas,documentsareperiodicallypurgedaspartof arecords-managementprocess.Other

storagemethodsshouldbeevaluatedtopreventdestructionof buildingdocumentation.Alackof proper

documentationwithrespecttostructureswithintheSFHAcanimpactacommunitysCommunityRating

System(CRS)scoreand,ultimately,itsNFIPstatus.
4-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

4 PERMITS AND INSPECTIONS

Thefollowingisabrief listof documentsthatshouldbeincludedinthepermitfile:

n Permit

ApplicationForm,includingallattachmentsandasiteplan

n Correspondence

relevanttopermitapprovalordenial

n A

copyof aFIRMetteatthetimeof application(includingFIRMpanelnumberandeffectivedate)

n Engineering

designsthatmayberequiredforenclosuresbelowtheBFE

Ð VZones:BreakawayWallCertifications

Ð AZones:EngineeredOpeningCertificationsormanufacturersdocumentation

n Engineering

calculationsforneworsubstantiallyimprovedbuildings

n Variances

andapplicabledenialorapprovaldocumentation

n Inspection

records

n 

As-builtlowest-floororlowest-horizontal-structural-memberdocumentation(forexample,EC)

n Certificate

of ComplianceorOccupancy

4.2.2.2 Record-keeping requirements:

TheI-Codesassertthefollowingspecificrequirementsregardingrecordkeeping:

n Section

104.7of theIBCrequiresthekeepingof allofficialrecordsfortheperiodrequiredforretention

of publicrecords.

n The

NFIPandIBCAppendixG103.8requirethatrecordsrelatedtodevelopmentinfloodhazard

areasbemaintainedpermanentlyandthatthoserecordsremainavailableforpublicinspectionand

review.Inadditiontoretainingpermitfiles,manycommunitiesmaintainaseparatelogof permits

issuedinfloodhazardareas.

n Section

R.104.7of theIRCrequiresretentionof officialrecordsof applications,permits,andcertificates

issued;reportsof inspections;andnoticesandordersissued.Suchrecordsaretobekeptfortheperiod

requiredforretentionof publicrecords.

4.2.2.3 Required Documentation

TheI-Codesrequirecommunitiestoobtainandretaindocumentationnecessarytodeterminewhether

floodplaindevelopmentactivitiesarecompliantwiththeI-Codes.Requirementsincludethefollowing:

n Documentation

of lowest-floorevaluations(IBCSections109.3.3and1612.5;SectionsR109.1.3and

R324.1.4)
FEDERAL EMERGENCY MANAGEMENT AGENCY 4-5

PERMITS AND INSPECTIONS 4

n Documentation

of floodproofing(IBCSection1612.5)

n Documentation

of thedesignof nonstandardfloodopenings(IBC

Section1612.5)

n In

certaincircumstances,documentationof breakawaywalldesign

(IBCSection1612.5;IRCSectionR324.3.6)

n Documentation

of foundationdesign,butonlyinfloodhazard

areassubjecttohigh-velocitywaveaction(IBCSection1612.5,IRC

SectionR324.3.6)

n Documentation

thatfloodwayencroachmentswillnotincreaseflood

levels(IBCAppendixG,SectionG103.5).AppendixGappliesonly

if itspecificallyreferencesthisinthelocalcodeorordinance.

n Notifications

providedtoadjacentcommunities,thestate,and

FEMAforwatercoursealterations(IBCAppendixG,Section

G105.7(5))

n Copies

of inspectionreportsforbuildingslocatedinfloodhazardareas(IBCAppendixG,Section

G103.8;IRCSectionsR104.7andR109.1.3)

4.2.2.4 Plan Review and Inspection Checklist

Somecommunitiesuseachecklistduringplanreviewtoverifythatappropriateflood-resistantprovisions

havebeencheckedandareacceptable.Thesample-planreviewchecklistsintheAppendixtothisguide

aredesignedtobetransferredtotheinspectionstaff andutilizedtodocumentthatspecificflood-resistant

constructiondetailswereacceptable.UsingachecklistisnotanNFIPrequirement;however,itsuseisa

sensiblewaytodocumentplanreviewandcompliance.

4.3 Freeboard

Freeboard(i.e.,theadditionalelevationabovetheBFE)shouldbeaseriousconsiderationforany

communitywithfloodingrisks.Incorporatingfreeboardrequirementsintoacommunitysregulationscan

occureitheratthestateorlocallevel.If thecommunityhasadoptedASCE24-05asastandard,itshould

bereviewedinordertomakesurethatthefreeboardrequirementswithinitarefollowed.Freeboardthat

exceedstheminimumNFIPrequirementscanbeavaluabletooltothecommunityinmaintainingNFIP

compliance.Somebenefitsof freeboardare:

n Lower

floodinsurancepremiums

n Additional

protectionforeventsexceedingthepredicted100-yearfloodeventelevation

n Allows

forfuturechangesorupdatestoFIRMs

n Allows

foraccurateinterpretationof floodprofiles

NOTE

Many certifications may be 

required; the following are 

specific to coastal design and 

construction projects:

Pile or column certification 

is required for buildings in 

SFHAs subject to high-velocity 

wave action.

Breakaway wall certification 

is required if design loads are 

consistent with the values set 

forth in the code.

Flood opening certification is 

required if flood openings do 

not conform to the prescriptive 

code specifications.
4-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

4 PERMITS AND INSPECTIONS

n Allows

forissuesrelatedtosurveyingbenchmarksthatmayhavemoved

n Allows

forerrorsinthelowestfloorelevationduringconstructionwithoutcompromisingtheBFE

n Allows

forchangesinwaterlevelsduetosubsidenceorsealevelchange

Evenif afreeboardpolicyisnotinstituted,constructingabuildingtoanelevationgreaterthantheBFE

willreducethepropertyownersfloodinsurancepremium.Asof 2009,theIBCwillrequirefreeboard.

InDecember2006,areporttitledEvaluationof theNationalFloodInsuranceProgramsBuildingStandards

wasreleased,whichevaluatesthebenefitsof utilizingfreeboard.ThereportisavailablethroughFEMAs

onlinelibrary.

4.4 The Pre-development Conference/Pre-application Meeting

Thereisnosubstituteforeffectivecommunication.Alwaysencouragepermitapplicantstocallorvisit

buildingdepartmentstaff todiscussthedevelopment-permitandbuilding-permittingprocessand

requirementsbeforeapplicationsaresubmitted.Suchcommunicationestablishesanopportunitytoask

andanswerquestionsanddeterminewhetheraproposalfitsthatmunicipalityscoastaldevelopment

guidelines.Theprocessesormodificationsshownbelowmaywarrantconsiderationforlocalprograms:

n Inform

theapplicantif theprojectwillrequireapprovalthroughaplanningprocess.Whenever

possible,introducetheapplicanttotheplanningstaff.Aplanningapplicationandfeesmayberequired.

Explainhowthosefeesareconsideredseparatelyfrombuildingpermitfees.And,if required,inform

theapplicanthowplanningapprovalsmustbesecuredbeforetheapplicantisallowedtoapplyfora

buildingpermit.

n Encourage

theapplicanttodiscusstheprojectwiththepublicworksdepartment,firedepartment,

andhealthdepartment(orotherrelevantagencies)todeterminespecialrequirementsthatmaybe

necessitatedbythestructureslocationwithinanSFHA.Staff shouldbepreparedtooffersuggestions

tofacilitatethebuildingpermitprocess.

n If 

thereareadditionalrequirements,notifytheapplicantif thearchitecturalreviewcommission,board

of zoningappeals,orplanningcommissionneedstoconductareviewof thepermitapplicationor

drawings.Makeknowntheexistenceof anyFederal,state,regional,orlocalplanning,environmental,

andzoningreviewsandapprovalsthatmayberequiredbeforetheapplicantsubmitsapplicationfora

buildingpermit.Aflowchartmakestheinformationeasiertounderstandandmorelikelytobefollowed.

(SeeFigure4-1forageneralexampleof thepermittingsteps.Modifyingthestepsmaybenecessaryto

makethemconformtothelocalpermittingprocess.)

n Be

preparedtoanswerapplicantquestionsaboutcoastalconstructionrequirements.Keepcopiesof 

theseregulationsavailable.Whenpossible,assisttheapplicantindeterminingwherethepropertyis

locatedontheappropriateFIRMmap.Verifythefloodelevationsandexplainhowthisinformation

isincorporatedintotheDFE.Drawingsorillustrationscanclearlyconveysuchinformation.Advise

theapplicantof therequiredbasicwindspeedandexplainwhythisinformationiscriticaltothe

designprocess.
FEDERAL EMERGENCY MANAGEMENT AGENCY 4-7

PERMITS AND INSPECTIONS 4

n To

minimizestaff timespentansweringtypicalapplicantquestions,keepanamplesupplyof 

informationalbrochuresonpermittingrequirementsavailableatthepermittingcounterandpostthat

informationonthelocalWebsite.Trainyourstaff tobecomeknowledgeableintheserequirements,

sothatsomeoneisalwaysavailabletoeffectivelyscreenwalk-intrafficand,if appropriate,provide

appropriateguidancetoapplicants.Also,makealistof outsideagenciesanddepartmentcontacts

available,completewithnames,phonenumbers,ande-mailaddressesof whoshouldbecontacted

aboutparticularrequirementsandprocedures.

n When

evaluatingFIRMswiththeclient,makeclearthatthelocationdeterminationinanSFHAis

nearlyalwaysbaseduponthestructurelocationonthemapandnotonthestructureselevation.The

BFEinrelationtotheactualgroundelevationsetsthefloodplainlimitsforregulatorypurposes.When

groundsurveysshowthatadevelopmentsitsabovetheBFE,thelocalofficialcanrecordthedata

andissuethepermit;then,if thedeveloperorownerwantsthepropertyremovedfromtheSFHA

designation,aLetterof MapAmendment(LOMA)canberequested.Conversely,if sitesurveysshow

thatareasconsideredoutsidethe100-yearfloodplainonpublishedmapsare,infact,belowtheBFE,

thelocalofficialshouldrequireprotectionof newbuildingstotheBFE.Althoughasitemaytechnically

belocatedoutsidethemappedSFHA,thelocalofficialshouldnotignoretheknownfloodhazard.This

mayrequiremodificationstothelocalordinancesinordertomakethisenforceable.

n It

isatthistimethatmanyapplicantshavequestionsaboutLOMAsandLettersof MapRevisionFill

(LOMR-F).ExplaintotheapplicantthataLOMAisbasedupontheelevationof thenatural

groundof thelowestadjacentgrade.ALOMAcanbeissuedforeitherastructureoralot,butthe

advantagesanddisadvantagesof theseoptionsshouldbediscussedwiththeapplicant.If fillmaterial

willbeadded,aLOMR-Fmustbeissued.AdeterminationwillneedtobemadeforaLOMR-Fin

ordertodeterminewhetherthestructurewillbereasonablysafefromflooding,asdirectedbythe

NFIP.ThesemaprevisionsoramendmentsareintendedtocorrectproblemswithFIRMsandnotto

relinquishtheresponsibilityof thepropertyownertomaintainfloodinsurance.

n Notify

applicantsrequestingsignificantimprovementsthattheentirestructuremustbebroughtinto

compliance.Refertheapplicanttoaprofessionaltoevaluatethestructureanddeterminewhetheritis

asubstantialimprovement.(SeeSection3.1.1foradefinitionof substantialimprovement.)

n Because

thepermitprocesscanbecomplex,itssuccessfulcompletion

dependsheavilyupontheavailabilityof thelocalofficialtodispense

clearandconciseexplanations.Thisisalsoanopportunetimeto

suggesthiringtheservicesof alicensedprofessional,depending

upontheprojectsizeandtype.Infact,theentireproject(orportion

thereof)mayrequiretheprofessionalservicesof alicensedsurveyor,

architect,orengineer.Rememberthateitheraregisteredsurveyor

orengineermustalwaysdetermineandcertifythe100-yearflood

elevationof alldevelopmentapplicationsfornewconstructionor

structuraladditionslocatedwithintheSFHA.

NOTE

Recent FEMA programs to 

reissue Flood Insurance Rate 

Maps have raised the BFE 

in some areas. Substantial 

improvements and repairs 

require the entire structure 

to be compliant, while minor 

improvements and repairs 

require only that the lowest floor 

be built to the elevation required 

for the structure when it was 

initially constructed. An original 

Elevation Certificate will be 

required for this.
4-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

4 PERMITS AND INSPECTIONS

4.5 Coastal Construction Permit Application Steps

Onceabuildingpermitapplicationissubmitted,sixgeneralprocessingstepsshouldbefollowed:

1.Performinitialapplicationreviewandcollectfees.

2.Routetheapplicationtootherdepartments/agenciesforreviewandcomments.

3.Collectcommentsandrecommendationsregardingapprovalsordenials.

4.Reviewtheapplicationsabilitytomeetalltechnicalbuildingrequirements.

5.Approveordenytheapplication.

6.Informtheapplicantof anyappealprocesstopursue(if necessary).

Figure4-1,PermittingProcessOverview,illustratesagenericprocessdesignedtoprovidesuggestionson

possibleprocessmodifications.

4.6 Permit Plan Submittal Requirements

Thepermitapplicationpackagemustincludesufficientplansheets

andsupportdocumentstoallowacompletestaff reviewandanalysis

duringtheinitialplancheck.Undernocircumstancesshould

incompletesubmittalseverbeaccepted.Noteapplicationdeficiencies

insuchsubmittalsandreturnthemimmediatelytotheapplicantfor

revisionsorresubmission.Itisthesoleresponsibilityof theapplicant

tosubmitacompleteapplication.Usinganinitialplan-reviewchecklist

isrecommendedtoassistinperformingtheintakereview.(SeetheAppendixtothisguideforasample

intakechecklist.)Useof achecklistwillidentifyobviousdeficienciesthatneedcorrectionorwillconfirm

thattheapplicationiscompleteandreadyforrigorousreview.

Plan-submittalrequirementsandpackagescanvarywitheachjurisdiction.Requirementscanrange

fromamodestsingle-pagereporttoalengthydocument.Allsubmittals,however,mustaddresscoastal

developmentissues,anditisrecommendedthattheyincludeanEC.(SeetheAppendixtothisguide

forexamples.)

Thefollowingsituationsorconditionsmayrequirethatcertifieddocumentsaccompanythepermitplan:

n Floodway

Encroachment.If anypartof theproposedprojectwillbelocatedinadesignatedfloodway,

theapplicantmustsubmitanengineeringcertificateanddocumentation(e.g.,aNo-ImpactCertificate)

demonstratingthattheproposedencroachmentwouldresultinnoincreaseinbasefloodheights.

n Enclosures

belowtheLowestFloor.Whenanapplicantdesignsanenclosurebelowthelowestfloor

(usinganalternativetotheminimumstandardforopeningsprescribedinNFIPrequirements),

aregisteredprofessionalarchitectorengineermustcertifythedesign.(SeeASCE24-05and

FEMANFIPTechnicalBulletin1:OpeningsinFoundationWallsandWallsof Enclosures(FIA-TB-1)for

informationonengineeredopenings.)

NOTE

Many communities attach a 

blank FEMA Elevation Certificate 

to the issued permit and clearly 

indicate when (during the 

process) it must be completed 

and submitted.
FEDERAL EMERGENCY MANAGEMENT AGENCY 4-9

PERMITS AND INSPECTIONS 4

Applicant 

Prepares

Application

Applicant revises

application

Record submission

and collect fees

Building code review Applicant revises

application

Plan modifications

Obtain BFE at project

site from FIRM, FIS

or other source

Verify that lowest

applicable elevation

(FFE or Lowest Horz. Member)

is at or above BFE

Verify that structure

will not impact

floodway

Building Permit

issued

Applicant begins

construction

Site inspection

conducted

Construction

violations

Corrections made

Zoning Review

Locate site on FIRM

Verify the application

meets NFIP and local

ordinance for development

Is the project

new or substantial

improvement?

Verify that the lowest applicable

elevation (FFE or Lowest

Horz. Member) is at or above BFE

Verify that NFIP

regulations have been followed

Final Inspection

Issue Elevation Certificate

Create/Submit

Final Record and

place in storage

= Issues to be resolved = Flow of work Items of work Coastal/Riverine specific

 items of work

Figure 4-1.

Permitting process overview.
4-10 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

4 PERMITS AND INSPECTIONS

n V

ZoneConstruction.AnapplicantproposingtoconstructabuildinginaVZonemustsupplya

statementfromaregisteredprofessionalarchitectorengineercertifyingthedesignandmethodof 

constructionof theelevatedbuildingandthedesignof breakawaywalls(if theloadresistanceexceeds

20poundspersquarefoot).Anas-builtcertificateisalsorecommended.

If freeboardhasbeenadopted,verifythatthecontractororengineerhassubmittedplansforabuilding

withthelowesthorizontalstructuralmemberthatisabovetheDFE.

4.7 Elevation Certificates

AlthoughanElevationCertificate(EC)isnotrequiredtoparticipatein

theNFIP,communitiesarerequiredtomaintainrecordsof eitherthe

lowestfloorelevationor,inVZones,arecordof thelowesthorizontal

structuralmember.CommunitiesareencouragedtousetheEC,

whichisrequiredtodeterminefloodinsurancerates.ECsarerequired

foracommunitytoparticipateintheCommunityRatingSystem

(CRS).Afteracommunitysinitialdateof application,allbuildings

constructedorsubstantiallyimprovedwithintheSFHAmusthaveanEC.Thelowestfloorelevation,or

thebottomof thelowesthorizontalstructuralmember,isthemostsignificantelementindetermining

whetherbuildingconstructioniscompliantwithlocalfloodplainmanagementrequirements.Certain

groundandbuildingelevationsaretobesurveyedandcertifiedsothatbuildingofficialscandetermine

theelevationof thelowestfloor.Agoodresourceforunderstandingthecertificationanddocumentation

of elevationsistheFloodplainManagementBulletinontheElevationCertificate(FEMA467-1).

Ideally,elevationsarecheckedwhenthelowestfloorlevelissetandbeforefurtherverticalconstruction

takesplace.Atthispoint,errorsintheelevationcanbecorrectedwithminimalcostanddelaybecause

thebuildingofficialsdocumentationof thelowestfloordependspartlyuponthelocationof utilities

andfinalsitegrading.Documentationof thefinalelevationsmustbecompletedandsealedwhenthat

workisfinished.

TheEC(FEMAForm81-31,February2006)isavailableonlineinthelibrarysectionof theFEMA

Website(http://www.fema.gov/business/nfip/elvinst.shtm).Theformhasspecificinstructionsand

illustrationsforthesurveyor/engineerandbuildingofficial.Itisexpectedthatanewversionof theEC

willbecomeavailablesometimeinearly2009.

Surveyor/Engineer.Aregisteredprofessionalwhoislicensedtoperformelevationsurveysisrequired

tocomplete,sign,andaffixaprofessionalsealtothedocumentationof elevations.Thedocumentation

mustbedatedtoindicatewhentheelevationsweresurveyedbecausecontinuingconstructionorfuture

modificationscouldalterand/oroutdatetheinformationshown.Theregisteredprofessionalisresponsible

forobtainingandcertifyingtheaccuracyof keygroundandbuildingelevations.

UsingFEMA-provideddiagrams,theregisteredprofessionaldetermineswhichbuildingelevationsto

surveybyselectingthebuildingdiagramthatmostcloselyrepresentstheactualbuilding.If thediagrams

donotmatchthebuildingconfiguration,theregisteredprofessionalmayneedtonotethiswithinthe

commentsectiontoclarifythediagramselected.

NOTE

As of January 1, 2007, additional 

photographs are required with 

the submittal of an EC. Refer to 

the FEMA Web site for further 

direction on what photographs 

are required for a particular site.
FEDERAL EMERGENCY MANAGEMENT AGENCY 4-11

PERMITS AND INSPECTIONS 4

Whentherequiredelevationshavebeensurveyed,thelocalofficialresponsibleforNFIPcompliancethen

determineswhichlevelisthelowestfloorandcomparesitsas-builtelevationtotheDFE.Thiscomparison

determineswhetherthebuildingiscompliantwiththeelevationprovisionsof thecodeordinanceor

rulesgoverninglocalNFIPcompliance.If thebuildingisnotcompliant,enforcementactionshouldbe

initiatedimmediately.

Indeterminingthelowestfloor,twofactorsshouldbekeptinmind:

n In

AZones,if anenclosedareabelowanelevatedbuildinghasfloodopenings,incorporatesfloodresistant

materials,andisusedonlyforparking,buildingaccess,orstorage,thenthefloorof thatarea

isnotconsideredthelowestfloor.If thestructurehasabasement,thebasementwillbeconsideredthe

lowestfloor.

n In

VZones,if anenclosedareabeneathanelevatedbuildinghasbreakawaywalls,flood-resistant

materials,andisusedonlyforparking,buildingaccess,orstorage,thenthefloorwithintheenclosure

isnotconsideredthelowestfloor.

Acopyof thedocumentationof elevations(forexample,theFEMAEC)mustbekeptinthecommunitys

permanentpermitfile.TofacilitatetheirreportingtoFEMAandthestate,somecommunitieskeep

aseparatelogwithinformationrecordedforfloodhazardareapermits.Atalaterdate,if elevation

documentationisnotinthefile,thecommunitywillberequiredtoobtainareplacementtoverifythe

properadministrationof NFIPrequirements.

4.8 Inspections

Evenwhenbuildingpermitsandconstructionplansarecomplete,goodinspectionandenforcement

proceduresareimportant.Buildinginspectors,codeofficers,andfloodplainmanagementofficialsmust

understandtheflood-resistantdesignandconstructionrequirementstheyaretocheck.If deviationsfrom

thepermitconditionsarefoundearlyduringconstruction,itiseasiertoworkwiththeownerandbuilder

toachievecompliancethroughcorrectiveactions.

Usingaplanreviewandinspectionchecklistcanfacilitateinspectionsbecausetheinspectorwillhavea

standardizedsummaryof flood-relatedrequirementsthatarenotseeninnon-floodplainbuildings.A

planreviewisalsohelpfulwhencodeenforcementandfloodplainmanagementarelocatedindifferent

officesoragencies.Achecklistalsodocumentstheinspection,whichcanbecrucialtomaintaininga

communitysgoodstandingwithintheNFIP.

Thesectionsbelowsummarizesomeof theinspectionsthatcanbeperformedtofacilitatecompliancewith

flood-resistantprovisionsof thecodeorlocalordinance.NotethatthislistusesDFE.If yourcommunity

doesnotusefreeboard,thenBFEisappropriatetouse.
4-12 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

4 PERMITS AND INSPECTIONS

4.8.1 Stake-out or Site Inspection

Thebesttimetoverifythatabuildingwillbelocatedcorrectlyisduringasiteinspection,whensetbacks

anddistancesfromthefloodsourceorbodyof watercanbechecked.Checkingthatthelowestfloor

isproperlyelevatediseasierif anelevationbenchmarkorreferencemarkislocatednearby.If oneof 

thereferencemarksshownonthefloodhazardmapisnotclosetothesite,placementof atemporary

onsitereferencemarkcanmakeiteasiertochecktheelevationwhenthefloorlevelisset;aregistered

professionalwillcertifytheelevationwhentheas-builtdocumentationof elevationsiscompleted.

4.8.2 Fill Inspection

WhenallowedinSFHAs,fillthatisplacedtostructurallysupportabuildingshouldbeinspectedfor

compaction.Compactionreportscreatedduringthefillplacementmonitoringshouldbecollected.Itis

alsoimportanttocheckthatthefinalelevationof thefillisinlinewithelevationdataincludedonthe

permitbecauseitwillaffectthefinalelevationof thelowestfloor.

4.8.3 Footing or Foundation Inspection

Forfoundationsthatwillcreateenclosuresbelowotherwiseelevatedbuildings,inspectorsshouldcheckfor

thespecifiednumber,size,andlocationof floodopenings.Thebottomof eachopeningshallbenogreater

than1footabovegradeandshouldnotbeconfusedwithunder-floorairventilationopenings,whichare

locatedjustunderthefloorlevel.Forslab-on-gradebuildings,thelowestfloorinspectionisconductedat

thistime.Forpile-supportedstructures,embedmentdepthandpileplumbnessshouldbechecked.Inall

cases,properconnectionsbetweenthewallsandfloor/foundationsystemsshouldbechecked.

4.8.4 Lowest Floor Inspection (Floodplain Inspection)

UnderSections109.3.3of theIBCandR109.1.3of theIRC,thedocumentationof thelowest-floor

elevationistobesubmittedtothebuildingofficial.Animportantpartof administeringprovisionsfor

flood-resistantconstructionisensuringthatbuildingsareelevatedproperly.Thisisrequiredwhenthe

lowestfloorelevationissetandbeforefurtherverticalconstructiontakesplace.Anerrorof 1or2feet

inelevationmayseemminor;however,correctioncanbeexpensiveandcomplicatedif thaterroris

discoveredoncethewallsandroof areinplace.Inaddition,Federalfloodinsuranceisverycostlyfornew

buildingsconstructedwiththeirlowestfloorslocatedbelowtheBFE.TheLowestFloorInspectionisalso

agoodopportunitytoverifythatthemechanicalandelectricalutilitiesaretobeplacedabovetheBFE.

4.8.5 Final Inspection

Afinalinspectiontodocumentcompliancewiththefloodplainmanagementrequirementsof thelocal

codesandordinancescanbeconductedatthesametimeasthefinalinspectionthatprecedestheissuance

of theoccupancycertificate.Duringthatinspection,itisimportantto:

n Verify

thatutilitiesandotherbuildingelementsarelocatedproperly,usuallyabovetheDFE.Frequently

overlookeditemsincludeheating,cooling,andventilationequipment;electricaloutlets;plumbing

fixtures;andductworkthatisinstalledunderthefloor,usuallywithinacrawlspace.
FEDERAL EMERGENCY MANAGEMENT AGENCY 4-13

PERMITS AND INSPECTIONS 4

n In

AZones,inspectenclosuresbelowelevatedbuildingstoensure

thatthefloodopeningsarecorrectinnumberandtoconfirmtheir

totalnetopenareaandplacement.If standardairventilationunits

areusedasfloodvents,theclosuremechanismmustbepermanently

disabledsothatfloodwatercanautomaticallyenterandexitfreely

withnohumanintervention.

n In

VZones,inspectenclosuresbelowelevatedbuildingstodetermine

thatbreakawaywallsareconstructedtofreelybreakawaywithout

causingdamagetothebuildingsfoundationortheelevated

portionof thebuilding.Tominimizetransferof loadsduringflood

conditions,utilityconnectionsshallnotbemountedon(orpenetrate

through)breakawaywalls.

n For

enclosedareasbelowtheDFE,checkthattheapproveduse(e.g.,parking,storage,andbuilding

access)appearstobeconsistentwithwhathasbeenpermitted.

n Check

thattheexteriorfill,whenpermitted,isplacedaccordingtoapprovedplansandspecifications.

n Verify

thatflood-resistantmaterialsareusedbelowtheDFE.SeeFEMANFIPTechnicalBulletin2:

FloodDamage-ResistantMaterialsRequirementsforBuildingsLocatedinSpecialFloodHazardAreas(FIA-TB-2).

n Examine

buildingutilitiestodetermineif theyhavebeenelevatedorotherwiseinstalledaccordingto

planstoresistflooddamage.Heatpumpsandpad-mountedairconditioningunitsmustalsobeelevated

atorabovetheDFE.

n Collect

theas-builtdocumentationof elevationsbeforethefinalsign-off.

n If 

used,completeandsigntheplanreviewandinspectionchecklistandplaceallinspectionreportsin

thepermitfile.

4.8.6 Post-Damage Inspections

Afteraflood,hurricane,oranynaturalhazardeventthatcausessignificantdamage,buildingslocated

inSFHAsandotherdamagedbuildingsoutsideof theSFHAsshouldbeinspected.Somecommunities

distributeflyersexplainingpermitrequirementsforreconstructionorrepairingbuildingsandhowfuture

flooddamagecanbereducedduringtherepairprocess.Mosthomeownersdonotrealizethattheymay

needpermitstorepairandrestoredamagedbuildingsif theyarelocatedwithinSFHAs.Damagethat

maymeetthesubstantialdamagedefinitionmustbeaddressedinaccordancewiththeapplicable

provisionsof thebuildingcodeandfloodplainmanagementordinanceineffect.(SeeSection3.6.)

Manytoolsareavailabletocommunitiesfollowingnaturaldisasterstoevaluatedamagelevels.Buildings

needtobeevaluatedinordertodeterminewhethertheyaresafetooccupy.TheAppliedTechnology

CouncilhasissuedATC-45FieldManual:SafetyEvaluationof BuildingsAfterWindStormsandFloods(2004)which

providesamethodologyforevaluatingbuildingsfollowingastormeventandmakingadetermination

onwhethertheyaresafetooccupy.MoreinformationcanbefoundregardingATC-45ontheApplied

TechnologyCouncilWebsite(http://www.atcouncil.org).

NOTE

Communities are encouraged 

to consult with either the 

NFIP State Coordinator or the 

appropriate FEMA Regional 

Office prior to issuing variances. 

A variance should be carefully 

considered. Even if allowed by 

a variance, NFIP flood insurance 

on a building that is only 1 or 

2 feet below the BFE may cost 

two to three times more than a 

building in which the lowest floor 

is located at or above the BFE.
4-14 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

4 PERMITS AND INSPECTIONS

Thedeterminationof substantialdamageisanotherdecisionthatneedstobemadefollowingstorm

events.In1998,FEMAreleasedtheResidentialSubstantialDamageEstimator(RSDE)softwaretoassist

localbuildingofficialsinevaluatinghomesbasedupontheperformanceof 16buildingcomponentsduring

afloodingeventandexpeditingthemannerinwhichasubstantialdamageassessmentisconducted.

Informationonobtainingacopyof theRSDEsoftwareandsupportmanualscanbefoundonthe

FEMAWebsitehttp://www.fema.gov.TheNationalFloodMitigationDataCollectionTool(NFMDCT)

providesameansforcatalogingandtrackingthesubstantialdamagewithinacommunityorjurisdiction

andsubmittingthatdata.

4.8.7 Coastal and Floodplain Construction Inspector Certification

Aspartof theICCsinspectioncertificationprogram,theICChasaddedacertificationdesignationfor

acertifiedcoastalandfloodplainconstructioninspector,whichwasspecificallydevelopedinordertoaid

theprocessof conductingbuildinginspectionsforcoastalareas.Thiscertificationfocusesonthefollowing

areas:

n General

constructionprovisions(e.g.,foundations,siting,shearwalls,productapprovals,erosion,special

inspections,andcorrosioncontrol)

n Special

high-windprovisionsandloadpathcontinuity

n SFHAs

n Detached

andattachedaccessorystructures

n Government

regulations

AdditionalinformationonobtainingthiscertificationcanbefoundontheICCWebsiteat

http://www.iccsafe.orgintheCertificationandTestingsection.

4.9 Enforcement and Violations

Properenforcementof floodplainmanagementprovisionsisacriticalpartof acommunitysresponsibility

undertheNFIP.Duringconstruction,violationsof theseprovisionsmustberesolvedassoonasthey

arediscoveredandbeforefurtherconstructionoccurs.Whatmayappeartobeaminorviolationcould

provecostlywhentheownerpurchasesNFIPfloodinsurance.AcommunitysstandingintheNFIP

dependsuponmakingagood-faithefforttosuccessfullyresolveviolations.Byallowinganyviolation

togounresolved,thecommunitymaysetaprecedent,makingitmoredifficulttotakefuture

enforcementactions.

Perhapsoneof themorepersuasiveargumentsforadoptingtheI-Codesisthatdoingsoprovidesan

opportunitytoconsolidateenforcementauthorityforflood-resistantdesignandconstructionprovisions.

Thebuildingdepartmenttypicallyhasmechanismsinplacetoaggressivelyhandlecodeviolations,while

planningandzoningdepartmentsmaynot.
FEDERAL EMERGENCY MANAGEMENT AGENCY 4-15

PERMITS AND INSPECTIONS 4

Whenthebuildingofficialandthefloodplainmanagerarelocatedinthesamedepartment,careshouldbe

takenbythebuildingofficialandstaff toenforceproperpermittingrequirementsonnewandimproved

constructionandtoverifythatancillarystructuresonapropertyarenotadverselyalteringthefloodplain.

Enforcementof thesepermitsallowslocalofficialstoevaluatethepotentialimpactsof suchstructures

andtheiraffectonwaterflowanddrainagewithinthefloodplain.

If adeveloperorpropertyownerdoesnotcomplywiththebuildingdepartmentsrequestsforcompliance,

thepermitapplicantshouldfirstbenotifiedinwriting.Anoticeshouldbeissuedonthepropertyif 

adjustmentsarenotmade.Thefinalstepintheinitialprocessmayincludewithholdingthecertificateof 

occupancy.Thefollowingoptionsareavailabletoensurecompliancetothebuildingcodeanddevelopment

requirements:

n Fines

levied

n Housing

Court

n Injunctions

againstproceeding

n Recordation

Itisimportantthatthebuildingofficialdiscussestheseoptionswiththecommunityslegalcounselbefore

implementingaplanof action.If noneof theseoptionsyieldsapositiveoutcome,thefinaloptionisto

implementSection1316of theNationalFloodInsuranceActof 1968,asamended.If approvedbythe

FEMARegionalOffice,thepropertywillbedeniedfloodinsurance.Implementationof Section1316,

however,shouldbeconsideredonlyif allotheroptionsfail.

4.10 The Variance Process

Forpurposesof theNFIP,avarianceisagrantof relief fromtheapplicationof theNFIPfloodplain

managementrequirements.AvariancetotheNFIPorlocalfloodplainmanagementrequirementsallows

constructioninamannerthatisotherwiseprohibitedandisgrantedforfloodplainmanagementpurposes

only.Acommunitymayissueavariancetoallowabuildingtobeconstructedinamannerthatisat

variancetotheirapplicationof theminimumNFIPprovisionsvialocalordinances;however,NFIPflood

insurancewillstillberatedaccordingtoriskandmayproveprohibitivelyexpensive.

Theprimarygoalsof theflood-resistantprovisionsof thecodearetoreducedamageandprotectthe

publichealthandsafetyof theentirecommunity.Achievingthesegoalsalsoresultsinthecreationof 

disaster-resistantandlivablecommunities.Fewvariancestothefloodplainmanagementprovisionscanbe

justified.Avarianceshouldnotbegrantedif aproposedactivityincreasesthesusceptibilityof buildings

andpeopletofloodingandflooddamage.

Asaguidingprinciple,avarianceshouldpertaintotheuniquecharacteristicsof thelanditself or

considerationsforhistoricallysignificantstructures.Aproperlyissuedvariancemaybegrantedforaparcel

of landwithphysicalcharacteristicssounusualthatcodecompliancewouldcreateanexceptionalhardship

fortheapplicant.Avarianceshouldnotbegranted,however,baseduponthepersonalcircumstancesof 

anindividual.Itisimportantthatthebuildingofficialmaintainrecordsonvariancerequestsalongwith

recordsof acceptanceordenialattachedtothoserequests.
4-16 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

4 PERMITS AND INSPECTIONS

Somevariancesbecomenecessarybecauseof thepresenceof historicstructures(IBCSectionG105.3).

If astructurehasexperiencedsubstantialdamageandisunabletobeelevated,measuresshouldbetaken

tomitigatefuturedamage.Thebuildingshouldberepairedusingwater-resistantmaterialsand,wherever

appropriate,utilitiesshouldbemovedabovetheDFEtomitigaterepetitivelosses.Referenceguidesand

materialsareavailablethroughtheFEMAWebsite(http://www.fema.gov).

4.10.1 Variance Processes as Impacted by the IBC

Section112of theIBCrequiresaboardof appealstohearanddecideappealsof orders,decisions,or

determinationsmadebythebuildingofficial.Specificrequirements,considerations,andconditionsfor

issuingvariancefromfloodplainmanagementrequirementsarefoundinAppendixG(SectionG105)of 

theIBC.

4.10.2 Variance Processes as Impacted by the IRC

SectionR112requiresaboardof appealstohearappealsof orders,decisions,ordeterminationsmade

bythebuildingofficial.Theboardof appealshasspecificresponsibilitiesrelatedtofloodhazardarea

development:

n Section

R112.2.1.Determinationof substantialimprovementinareaspronetoflooding.Requiresthat

theboardof appealsevaluatethebuildingofficialsfindingregardingthevalueof proposedimprovements

toexistingbuildingstodeterminewhethertheworkconstitutesasubstantialimprovement.

n Section

R112.2.2.Criteriaforissuanceof avarianceforareaspronetoflooding.Setsforthspecific

criteria(consistentwithminimumNFIPrequirements)tobeappliedduringthereviewandconsideration

of variancestotheminimumfloodhazardareacriteria.

4.11 Supplemental Information

TheAppendixtothisguidehassamplepermitsandcheckliststhatwillaidinbetterunderstandingthe

process.Thesesamples,withpropermodifications,maybeusedbycommunities:

n Floodplain

DevelopmentPermit

n Elevation

Certificate

n V

ZoneCertificate

n Checklist

forPermitReview

n Checklist

forVZonePermitReview

n Checklist

forVZoneInspections

n Checklist

forAZonePermitReview

n Checklist

forAZoneInspections
FEDERAL EMERGENCY MANAGEMENT AGENCY 5-1

COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS 5

Coastal Construction and 

Continuous Load Paths

Chapters

1through4describethenaturalhazardspresentincoastalenvironments,regulations

applicabletothosehazards,andpermittingprocedurestoensurethatregulationsareimplemented

duringtheconstructionprocess.Chapters5through11discusshownaturalhazardsandregulations

affectbuildingdesignandconstruction

Acriticalaspectof hazard-resistantconstructionistheabilityof abuildingorstructuretocarryandresist

allloadsincludinglateralandupliftloadsfromtheroof,walls,andothercomponentstothefoundation

andintotheground.Theabilityof abuildingtoresistthesetypesof loadsdependslargelyupon

whetherthebuildingsconstructionprovidesacontinuousloadpath.

Thediscussioninthischapterfocusesonwindloads;however,thesameprinciplesapplytootherevents

(suchasearthquakes)thatcreateloadsonbuildings.Section2.2of FEMA232containsanexcellentdiscussion

of theloadpathcontinuityrequiredtoresistseismicevents.

Thelocationof continuousloadpathcomponentsisalsoimportant,

particularlyforthosecomponentsthatresistlateralloads.Ideally,

suchcomponentsshouldbelocatedsymmetricallywiththefootprint

of thestructure.Thismayrequirebuildingstobedesignedrectangular

inplanorconstructedwithrectangularsections.Theproper

useof rectangularelementsreducesplanirregularitiesandminimizes

thedevelopmentof torsional(i.e.,twisting)forceswithinthebuilding.

Torsionalforcescanoverloadstructuralelementsorcauseexcessive

deflectionthatcandamagenon-structuralbuildingcomponents.

Torsionalloadingandplanirregularitiesarecomplexissuesbeyond

thescopeof thisguide.(SeeFEMA232forguidanceonthoseissues.)

5.1 Continuous Load Path

Thetermcontinuousloadpathdescribesthestructuralconditionrequiredtoresistloadsactingonabuilding.

Abuildingmaycontainhundredsof continuousloadpaths.Thecontinuousloadpathstartsatthe

pointorsurfacewhereloadsareapplied,thenmovesthroughthebuildingitself,continuesthroughthe

foundation,andterminateswheretheloadsarefinallytransferredtothesoilsthatsupportthebuilding.

FEMA55describesacontinuousloadpathasatypeof chainwhoselinksconsistof themembers

andconnectionsthatmakeupabuilding.Aswithanychain,acontinuousloadpathisonlyasstrong

asitsweakestlink.Buildingslackingstrongandcontinuousloadpathsmayfailwhenexposedtoforces

fromcoastalhazards,thuscausingabreachwithinthebuildingenvelopeoreventhetotalcollapseof 

suchbuildings.

NOTE

For coastal buildings, wind 

and flood events will produce 

lateral loads that must be 

resisted. Seismic events also 

produce laterally induced loads 

through the structure. Complex 

floor plans and irregularities 

in the building structure may 

compound these forces. See 

FEMA 232 for guidance on 

seismic-resistant designs 

for homebuilders.
5-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

5 COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS

Continuousloadpathsareimportantinallbuildings.Incoastalconstruction,wherewindloadsare

higherandfloodloadsexist,payingproperattentiontocontinuousloadpathsiscrucialforensuring

buildingsurvival.

Thehistoryof paststormdamageisrepletewithinstancesof failuresinloadpaths(seeFigures5-1

through5-5).Repeatedly,buildingsconstructedalongthecoasthavefailedwhentheirloadpathswerenot

strongenoughtowithstandtheforcesexerteduponthem.Mostloadpathfailureshavebeenobservedat

connections,asopposedtofailureof theindividualmembersthemselves.Fortunately,asbuildingcodes

andstandardsimprove,theknowledgeof loadpathsincreasesandolderbuildingsareeitherimprovedor

replaced.Asaresult,loadpathfailuresarebecominglessfrequent.

Asstructuralsystemsperformbetter,otherissuesrelatedtoloadpathconstructionbecomeevident.Recent

post-disasterdamageinvestigationshaverevealedperformanceissuesinbuildingenvelopes.Chapters

8,9,and10presentdetaileddiscussionsonbuildingenvelopeperformanceforroofs,wallsystems,

andopenings.

Figure 5-1.

DADE COUNTY, FLORIDA, HURRICANE 

ANDREW (1992): Second-story 

wood framing (on first-story 

masonry). Load path failure at 

end gable. (Source: FEMA 55)

Figure 5-2.

NORTH CAROLINA, HURRICANE 

FRAN (1996): Load path failure in 

connections between home and 

its foundation. (Source: FEMA 55) 
FEDERAL EMERGENCY MANAGEMENT AGENCY 5-3

COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS 5

Figure 5-3.

PUNTA GORDA, FLORIDA: 

Roof framing damage and loss due

to load path failure at top of wall/roof 

structure connection. 

(Source: FEMA 488)

Figure 5-4.

PUNTA GORDA, FLORIDA:

Load path failure in connections

between roof decking and

roof framing. 

(Source: FEMA 488)
5-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

5 COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS

5.2 Types of Load Paths

Loadpathsrunfromthepoint(orsurface)whereloadsareapplied(seeFigure5-6)throughbuildingto

thefoundation,wheretheyaretransferredtothesoil.Inabuilding,thepaththatloadsfollow(i.e.,from

wheretheyareappliedtothestructuredowntothefoundation)dependsuponmanyfactors,suchasload

sharing,loaddistribution,andbuildingstiffness.Whileloadpathsarecomplex,designersconsiderthem

incategoriesof verticalorhorizontalpaths(seeFigure5-7and5-8).Mostdesigners,builders,and

homeownersunderstandthatdownwardgravityforcesmustberesistedbyverticalloadpaths.Vertical

loadpathsmustalsoresistupliftforcesfromflood,wind,orseismicevents.Largeupliftforcesmaybethe

resultof floodloadsfrombuoyancy,frombreakingwaveshittinghorizontalsurfaces(suchasdecksorthe

undersidesof buildings),orfromwindactingonallsidesof abuilding.Horizontalloadpaths,likevertical

loadpaths,transferlateralloadsfromwind,flood,andseismiceventsintotheground.

Aschematicexampleof acompleteloadpath(seeFigures5-7and5-8)showsthechainof connections

fromtheroof tothefoundation;theseconnectionsweredesignedandconstructedtoresistlateraland

upliftforcesfromawindevent.Theloadpathconsistsof fastenerssecuringtheroof covering(such

asroof shinglesandmetalroofing)totheroof deck;nailsorscrewssecuringtheroof decktotheroof 

framing;metalanchorssecuringtheroof framingtothewallstopplate;wallsheathingormetalstraps

securingthewallstopplatetowallstuds;andthewallstudsecuredtothebottomplate(orsillplate).The

loadpathcontinueswithanchorboltssecuringthefoundationbottomplatetothemainfloorbeamsand

thentothepilefoundation,inordertoaccountforallverticalandlateralloads.

Figure 5-5.

PASS CHRISTIAN, MISSISSIPPI: 

Newer home damaged from 

internal pressurization and 

inadequate connections. 

(Source: FEMA 549)

NOTE

FEMA 499 (Home Builder’s 

Guide to Coastal Construction 

– Technical Fact Sheet No. 

10, Load Paths) provides 

information and descriptions 

of continuous load paths.
FEDERAL EMERGENCY MANAGEMENT AGENCY 5-5

COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS 5

Allloadsappliedtoastructuremustbetransferredtothefoundationof thebuildingand,finally,the

ground.Itisimportanttoremember:

n Loads

actingonabuildingfollowmanypathsthroughthebuildingandmusteventuallyberesistedby

theground.Otherwise,thebuildingmayfailduringanevent.

n Loads

accumulateastheyareroutedthroughkeyconnectionsinabuilding.

n Member

connectionsareusuallytheweaklinkswithinaloadpath.

n Failed

ormissedconnectionscauseloadstobereroutedthroughunintendedloadpaths,oftenresulting

inbuildingdamageorcollapse.

Failuretoadequatelymaintainaproperloadpathhasbeenobservedwherebuildingelementsfailedafter

hurricanes.(Forexample,fastenerswerecommonlyspacedtoofarapart,weretoosmall,orhadweak

connections.)Numerousexamplesshowingfailurestofollowwell-establishedbasicconstructionpractices

exist,suchasensuringminimumedgedistancesforfasteners.

Figures5-7and5-8showacompleteloadpathandidentifywhattolookforwhenevaluatingplansor

inspectingframingandwhatbuildinginspectionpointstoaddress.Eachlinkisimportantandmustbe

consideredbytheengineerordesigner.Evenwithagooddesign,however,unsatisfactoryconstruction

of thestructurewillexertthemostimpactonthebuildingsperformanceduringastormevent.If the

constructionisnotcompletedinaccordancewithcodes,plans,anddrawings,theentirestructureremains

atrisk.Specificdetailsrelatedtofoundations,buildingframing,andthebuildingenvelopearediscussed

infollowingchapters.

5.3 Identifying Load Paths in Buildings

Itisimportanttoidentifybothverticaland

horizontalloadpathsinthebuildingdesignsand

duringconstructionof thebuilding.(Verticalload

pathswerediscussedinSection5.2.)

Horizontalloadpathsconsistof structural

elementsthattransferhorizontal(orlateral)loads

throughthebuildingtothefoundation.Horizontal

loadpathsinatypicalone-ortwo-familydwelling

consistof exteriorsidingthattransfersloadsto

wallsheathing;wallsheathingthattransfersloads

towallframing;wallframingthattransfersloads

tohorizontalroof andfloordiaphragms;and

horizontaldiaphragmsthattransferhorizontal

loadstothefoundationsthroughverticalshear

wallsandtheirshearwalltie-downs.

EXTERIOR WALL LOADING

(An exterior wall may be exposed to just

one load or a combination of loads shown)

LOAD TRANSFER

FIGURE 7-7

(IN PLANE)

GRAVITY

(IN PLANE)

Figure 5-6.

Loads applied to the exterior wall of a building.
5-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

5 COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS

HOME BUILDER’S GUIDE TO COASTAL CONSTRUCTION FEMA 499/August 2005 Technical Fact Sheet No. 10

Load Paths

Purpose: To illustrate the concept of load paths and highlight important connections in a wind uplift load path. 

Key Issues

• Loads acting on a building follow many paths through the building and must eventually be resisted by the 

ground, or the building will fail.

• Loads accumulate as they are routed through key connections in a building.

• Member connections are usually the weak link in a load path.

• Failed or missed connections cause loads to be rerouted through unintended load paths. 

Vertical load path from roof to ground on a platform-and-pile-construction building.

Note: Load paths will vary depending on construction type and design.

Adjacent framing members will receive more load if a connection fails. 

Figure 5-7.

Technical Fact Sheet No. 10, Page 1. For more information on load paths and load transfer, see Chapter 7. 

(Source: FEMA 499)
FEDERAL EMERGENCY MANAGEMENT AGENCY 5-7

COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS 5

Figure 5-8.

Technical Fact Sheet No. 10, Page 2. (Source: FEMA 499)

Shear Wall

Hold down

Connector

Horizontal

load path

Pile

Load Path

to ground

Strap

Floor

framing

Floor

beam

Bolts

Design wind 

uplift load 

path

5.4 Building Codes and Standards

Theimportanceof continuous(orcomplete)loadpathsisclearinbuildingcodesandstandards.Section

R301.1of theInternationalResidentialCode(IRC)states:

Buildingsandstructures,andallpartsthereof,shallbeconstructedtosafelysupportallloads,includingdead

loads,liveloads,roof loads,floodloads,snowloads,windloads,andseismicloadsasprescribedbythiscode.

Theconstructionof buildingsandstructuresinaccordancewiththeprovisionsof thiscodeshallresultinasystem

thatprovidesacompleteloadpaththatmeetsallrequirementsforthetransferof allloadsfromtheirpoint

of originthroughtheload-resistingelementstothefoundation.Buildingsandstructuresconstructedasprescribedby

thiscodearedeemedtocomplywiththerequirementsof thissection.
5-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

5 COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS

TheIRChasspecificdesignrequirementsformanypointswithintheloadpathsof buildingsforcertain

basicwindspeeds.Theserequirementscanbeusedbydesigners,builders,andcodeofficialstoselect

connectorsandsizeframingmembers.Becausetheprescriptivedesignsof theIRCarelimitedto110-

mphwindspeeds,otherstandards(suchasSSTD-10,StandardforHurricaneResistantResidentialConstruction,

theInternationalCodeCouncilsICC-600,ortheAmericanForestandPaperAssociations(AF&PA)

WoodFrameConstructionManual)canbeusedtoidentifyprescriptivesolutionsandconstructiondetailsin

areaswithhigherbasicwindspeeds.

TheIRC(andChapter23of theIBC)hasprescriptiveshearwallandshearwalltie-downrequirements

forconventionalconstructionasanalternativetoperformance-baseddesign(thatis,buildingswithlateralforce-resisting

systemsconsistingof horizontaldiaphragmsandshearwalls).Forbuildingsconstructed

withsteelorreinforcedconcreteframesorotherlateral-force-resistingsystems,theIBChasperformance

requirementsthatengineersandarchitectsusetodesignastructureslateral-force-resistingsystem.

TheprescribedloadsdiscussedaboveintheIRCgenerallyaddresswindandseismicloadsthatmustbe

consideredduringdesign.Incoastalareas,homesareoftenexposedtofloodloads,whichcaninclude

thosefrombreakingwaves,hydrostaticloads,hydrodynamicloads,andloadsfromfloodbornedebris.

Individualsresponsibleforplanreviewshouldbeawareof thislimitationtoensurethatallloadsarebeing

properlyconsideredduringbuildingdesign.Fewconsensuscodesorstandardshaveprescriptivefloodresistant

designs.FEMA550(RecommendedResidentialConstructionfortheGulf Coast:BuildingonStrongandSafe

Foundations),containsdesignsforseveralstylesof foundationssuitableforcoastalsitesandguidancefor

engineersindesigningcustomflood-andwind-resistantfoundations.

SimilarrequirementsexistinSection1604.4of theIBC:

...shallresultinasystemthatprovidesacompleteloadpathcapableof transferringloadsfromtheirpoint

of origintotheload-resistingelements.

SSTD10(theprescriptivehigh-windstandardforresidentialconstruction),alsorequiresloadpath

continuity,asdoesICC-600,StandardforResidentialConstructioninHigh-WindRegions.

5.5 Continuous Load Paths and Building Success

Post-eventassessmentsrevealhowconstructingbuildingswithstrongandcontinuousloadpathscan

enablestructurestosurviveevenwhenexposedtohurricane-forcewinds.

Fortheconstructionof acoastalbuildingtobeconsideredasuccess,thebuildingshouldmeet

fourconditions:

n It

mustbedesignedtowithstandanticipatedforcesandconditions.

n It

mustbeconstructedasdesigned.

n It

mustbeelevatedtoavoidfloodwatersandfloodforces.

n Its

envelopemustprotectthehabitableareasof thestructure.
FEDERAL EMERGENCY MANAGEMENT AGENCY 5-9

COASTAL CONSTRUCTION AND CONTINUOUS LOAD PATHS 5

Thedesignershouldonlyuseconnectionstotheirpublishedlateral/uplifttestedvalues.If theconnection

onlyhasatestedupliftvalue,useanotherconnectionthathasbeentestedfortheappropriatelateralforces

orutilizeadesignedalternativetoresistforces.

Figure 5-9.

BIG LAGOON, FLORIDA:

Elevated building (constructed 

to newer code) that 

survived Hurricane Ivan. 

(Source: FEMA 489)

Figure 5-11.

BIG LAGOON, FLORIDA: 

This house was elevated on piles, 

preventing major flood damage. 

(Source: FEMA 489)

Figure 5-10.

BIG LAGOON, FLORIDA: 

This house was elevated on 

piles, preventing severe damage 

from coastal flooding. 

(Source: FEMA 489)

FEDERAL EMERGENCY MANAGEMENT AGENCY 6-1

COASTAL FOUNDATIONS AND BEST PRACTICES 6

Coastal Foundations 

and Best Practices

6.1 Introduction

Abuilding

sfoundationisarguablyitsmostimportantstructuralelement.Despiteitsparticular

location,afoundationmustsupportthebuildingaboveitandalltheloadsthatareexertedonit.

Itmustadequatelytransferloadsactingonthestructuretothesupportingsoilsandmustresist

weathering,decay,andcorrosion(withlittleornomaintenance)inordertoremainviablefortheentire

lifeof thebuilding.Thefoundationmustperformallof thesefunctionswhilebeingexposedtothe

damagingeffectsandconditionspresentinacoastalenvironment.Theseeffectsincludeerosionand

scour,breakingwavesandmovingfloodwaters,andthepotentiallydisastrouseffectsof floodborne

debris.Coastalfoundationsmust,therefore,bestronger,betterplannedanddesigned,andmoresolidly

constructedthaninlandfoundations.

Ininlandareaswherewindandseismicloadsoftencontrolthedesign,thecriteriaforfoundationsare

well-definedandeasilyunderstoodbyengineers,architects,builders,andbuildingofficials.Codessuch

astheIBCandtheIRC(andtheirpredecessors)havefordecadesprovideddetailedrequirementsfor

foundationsandprescriptivefoundationdesignsformanystructures.Incoastalareas,however,thishas

notbeentrue.

Whilewindandseismiccriteriahavelongbeenestablished,floodcriteriaarenewerandhaveappeared

onlyrecentlyinperformance-basedconsensuscodesandstandards.Thefloodprovisionsof ASCE7

firstappearedinthe1995editionof thatstandard.Similarly,theconsensusstandardASCE24was

firstissuedin1998.Becausetheoriginationof floodprovisionsinperformancecodesandstandards

hasoccurredrelativelyrecently,flooddesignshaveyettomaketheirwayintoprescriptivecodesand

standards.Noconsensus-based,off-the-shelf,flood-resistantdesignsthatfullyaddressconstructionin

coastalareascurrentlyexist.DocumentssuchasFEMA259andFEMA550provideprescriptivedesign

guidanceforfoundations.FEMA499,TechnicalFactSheetsNo.11(FoundationsinCoastalAreas),No.12

(PileInstallation),andNo.13(WoodPile-to-BeamConnections)alsoprovideappropriateguidance.

Someaspectsof coastalenvironments,suchasscouranderosion,havenotbeenresearchedtothepoint

thatconsensuscodesorstandardshavebeendevelopedonthesetopics.Decisionsregardingsomecoastal

issues(e.g.,scouranderosion)mayneedtobebasedprimarilyonjudgmentfromlocaldesignprofessionals

orpublishedguidance,oronhistoricaldataandtrends.Intheabsenceof moredefinitivedata,decisions

mayneedtobebasedsolelyonlocalexperience.
6-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

6.2 Building Codes and Coastal Foundations

CoastalconstructionisregulatedinseveralIBCsections.IBCSection1603.1.6requiresthatwhena

homeislocatedwithinaSFHA,informationonlocalfloodconditionsandelevationsmustbespecified

intheconstructiondocuments.Whenahomeissitedinanareasubjecttohigh-velocitywaveaction

(i.e.,aVZone),theIBCalsorequiresthattheproposedelevationof thelowesthorizontalstructural

memberbespecified.IBCSection1612.4requiresthathomesinhigh-velocitywaveactionzonesbe

designedinaccordancewithASCE24-05,whichrequiresthatfoundationsbeconstructedtoresistall

floodforcesexertedonthem;remainfreeof obstructionsorattachmentsthatwilltransferforcestothe

structuralsystemorthatwillrestrictoreliminatefreepassageof high-velocityfloodwatersandwaves;

andbeconstructedof flood-resistantmaterials.ASCE24-05requiresthatstructuresinareassubjectto

high-velocitywaveactionbesupportedonpiles,columns,orshearwalls.Shallowmatorraftfoundations

maybeusedonlywhenthetopsof thosefoundationsareplacedbelowtheestimatedmaximum-eroded

groundsurface.ASCE24-05alsospecifiesfreeboard(thatis,requiresstructurestobeelevatedabovethe

NFIP-mandatedrequirements).Theamountof freeboarddependsupontheimportanceof thebuilding

andtheorientationof thebuildingsstructuralelementsinrelationshiptoincomingwaves.ASCE24-05

freeboardrequirementsgenerallyvarybetween1and2feet.

IBCSection1612.5(2)alsorequiresthatVZoneconstructiondesigndocumentsincludeastatementthat

thebuildingisdesignedinaccordancewithASCE24andthatthebuildingorstructuretobeattached

theretoisdesignedtobeanchoredtoresistflotation,collapse,andlateralmovementduetotheeffectsof 

windandfloodloadsactingsimultaneouslyonallbuildingcomponents,andotherloadrequirementsof 

Chapter16.Thisprovisionmayrequirearchitectsorengineerstodesignthefoundationforbuildings

locatedwithinVZones.

TheIRCrequirementsaresimilarbutsomewhatlessstringentthanthoseof theIBC.IRCSection

R324requiresthathomesbeelevatedandanchoredtoresistflotation,collapse,andlateralmovement;

IRCSectionR324.3.6requiresthatdesignprofessionalsprepareconstructiondocumentsstatingthatthe

designandconstructionmethodssatisfythefloodprovisionsof theIRC.Thefreeboardrequirementsof 

ASCE24-05,however,areinvokedonlywhenahomeisplacedwithinafloodway.Asabestpractices

approach,thefreeboardrequirementsof ASCE24-05shouldbemetforallcoastalconstruction(both

residentialandnon-residential).

6.3 Constructing Foundations in Coastal Areas

Buildingincoastalenvironmentsposesuniquechallenges:

n The

effectsof stormsurge,waveaction,anderosionmakecoastal

floodingmoredamagingthaninlandflooding.

n Buildings

areoftenrequiredtobeelevatedhigherthantheywouldbe

ininlandsitestoavoidfloodingandwaveaction,particularlyinareas

wherestormsurgecaninflictseveredamageonthebuildings.

n Foundations

areexposedtodamagingfloodbornedebristhatresultswhenfloodwatersdestroyolderor

weakerbuildingsandcoastalstructures.

NOTE

For information on Coastal 

A Zones, see Chapter 2 of this 

guide or Chapter 12 of FEMA 55.
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-3

COASTAL FOUNDATIONS AND BEST PRACTICES 6

n Erosion

andscourcanunderminefoundations,thuscausingbuildingstofail.

n Basic

(design)windspeedsaretypicallygreaterincoastalareasthanininlandareasandrequirebuildings

(andtheirfoundations)tobestrongerinordertoresistthosegreaterloads.

Incoastalenvironments,code-compliantfoundationsmustbedesigned

andconstructed:

n To

elevatethebuildinghighenoughtoavoidflooding.

n To

bestrongenoughtoresistallloadsexpectedtoactonthebuilding

anditsfoundationduringadesignevent.

n To

satisfytheminimumrequirementsof theNFIPandanystateor

localfloodplainmanagementconditions.

n To

preventflotation,collapse,andlateralmovementof thebuilding.

n With

flood-resistantmaterialsatorbelowtheBFE(orDFE,inareas

wheretheuseof freeboardismandated)

n So

thatthelowestfloor(inAZones)orthebottomsof thelowest

horizontalstructuralmembers(inVZones)areelevatedabovetheBFE/DFE

n To

accommodateexpectedscouranderosionthroughoutthelifeof thestructure

TheNFIPallowsconventionalfoundations(thatis,shallow,closedfoundationsequippedwithfloodequalizing

vents)inCoastalAZones;however,evaluationsconductedafternumeroushurricanes

confirmthatNFIP-allowedconventionalfoundationsoftenfailwhenexposedtobreakingwavesorwhen

underminedbyerosion.Becauseof this,VZoneconstructionisrecommendedforCoastalAZones.

AsdiscussedinChapter3of thisguide,VZoneconstructioninvolvesplacingstructuresondeep,open

foundationsthatelevatethelowesthorizontalstructuralmemberof thebuildingabovetheBFEorDFE

(seeFigure6-1).Figures6-2and6-3showexamplesof buildingfailureinanareawhereCoastalAZone

conditionslikelyexisted.

Theinlandextentof aCoastalAZoneisthelinewhereadesignfloodeventcancreatea1.5-foothigh

breakingwaveandisidentifiedonnewerFIRMpanelswithalinedifferentfromthefloodhazard

boundaryline;thislineiscalledtheLimitof ModerateWaveAction(LiMWA).(Thatboundaryis

delineatedwherestillwaterdepthsequalapproximately2feet.)Breakingwavesatthatboundarycan

destroyconcreteormasonryfoundationwallsthatlackadequatereinforcementtoresistwaveloadsfrom

thoserelativelyshort-breakingwaves.

NOTE

Some coastal areas mapped 

as A Zones may be subject to 

damaging waves and erosion. 

ASCE 24-05 defines Coastal A 

Zones as areas landward of V 

Zones or areas landward of an 

open coast, where breakingwave heights may exceed 

1.5 feet. (The V Zone/A Zone 

boundary on Flood Insurance 

Rate Maps denotes areas 

where design-event breakingwave heights reach 3 feet. 

When the wave is 3 feet high 

or higher, this area is mapped 

as a V Zone, while areas with 

waves less than 3 feet high 

are mapped as A Zones.)
6-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

Exceeding NFIP Elevation Requirements in Costal A Zones and V Zones

100-Year

Stillwater

Elevation

100-Year

Wave Crest

Elevation (BFE)

Toward Flood Source

Freeboard

Bottom of 

Lowest Horizontal

Structural Member

Figure 6-1.

Recommended open-foundation 

practice for buildings located 

within the Coastal A Zone and 

V Zone. (Source: FEMA 55)

Figure 6-2.

NAVARRE BEACH, FLORIDA: 

Slab-on-grade foundation failure due 

to erosion and scour undermining. 

(Source: FEMA 489)
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-5

COASTAL FOUNDATIONS AND BEST PRACTICES 6

6.4 Elevating Buildings in Coastal Areas

Buildingsincoastalareasmaybeelevatedinmanyways.Homescanbeelevatedonfill,constructed

withclosedfoundations(forexample,crawlspacefoundations,stemwallfoundations,orslab-on-grade

foundations),orconstructedonopenfoundations(usingpiers,pilings,orcolumns).Notallelevation

methods,however,aresuitableforallcoastalareas.Infact,severalmethodsareprohibitedinVZones,

whilesomemethodsareallowedbutnotrecommendedforusewithinothercoastalareas.Thissection

discussesthefoundationtypesusedtoelevatebuildingsandtheacceptabilityof eachstylewithina

coastalarea.

6.4.1 Elevation on Fill

BeforebuildingonasitewithinanSFHA,thesiteitselfcanbeelevatedwithfill(seeFigure6-4).Fill

canelevateasiteabovetheBFEandthusreleasethebuilderfromhavingtocomplywithcertainNFIP

constructionrequirements.Alternatively,fillmaybeusedtopartiallyelevatethesiteandallowshorter

NFIP-compliantfoundationstobeused.Shorterfoundationsimprovebuildingaccessibilityandare

oftendesirablefortheelderly,handicapped,orotherswithphysicalchallenges.

Becausefillissusceptibletoerosion,itisnotalwaysthebestoptiontomitigatefloodhazards.Itsuseis

prohibitedasameansof providingstructuralsupporttobuildingsinVZonesandisnotrecommendedin

CoastalAZones.Fillmaynotbeusedasameansof elevatingbuildingsincoastalareassubjecttoerosion,

waves,orfast-movingwater.

Figure 6-3.

NAVARRE BEACH, FLORIDA: 

Close-up of foundation failure 

shown in Figure 6-2. 

(Source: FEMA 489)
6-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

6.4.2 Closed Foundations

Aclosedfoundationtypicallyconsistsof continuousperimeter

foundationwalls.Becausethesewallsencloseareaswithinsolid

perimeterwalls,thisisoftenreferredtoasaclosedfoundation.

Aclosedfoundationcanbeacrawlspacefoundation,astemwall

foundation(usuallyfilledwithcompactedsoil),oraslab-on-grade(or

monolithic)foundation.

Aclosedfoundationobstructsfloodwatersanddoesnotallowwaterto

passeasilythroughafoundation.Closedfoundationsalsopresentlarge

surfaceareasuponwhichwavesandfloodforcescanact.Becauseof 

theirvulnerabilitytobreakingwaves,theuseof closedfoundationsisprohibitedwithinVZonesandisnot

recommendedwithinCoastalAZones.

ProperlydesignedandconstructedclosedfoundationsaresuitableforSFHAswheretheheightsof 

breakingwavesarelessthan1.5feet(i.e.,non-coastalAZones).Intheseinstances,thefoundationwalls

mustbeequippedwithopeningsthatallowwatertoentertheareaenclosedbythewalls.Theopenings

arenecessarytokeepunbalancedloadsfromoccurringduetothepresenceof floodwatersoutsidethe

walls(andnotinsidethem).Theopeningsallowwatertoenterandexittheareabehindthefoundation.

Theflowof floodwaterintoandoutof thefoundationequalizeswateronbothsidesof thewall.This

equalizationsignificantlyreduceslateralhydrostaticforcesonthewalls.FEMA499,TechnicalFactSheet

No.15,FoundationWalls,andFEMANFIPTechnicalBulletin1:OpeningsinFoundationWallsandWallsof 

Enclosures(FIA-TB-1),containinformationonfloodopeningsforclosedfoundations.

Figure 6-4.

PLAQUEMINES PARISH, LOUISIANA: 

Home that had been elevated 

on fill, during the aftermath 

of Hurricane Katrina. 

(Source: FEMA 549)

NOTE

Although the NFIP permits 

closed foundations in A Zones, 

they are not recommended in 

Coastal A Zones. The walls 

of these foundations will be 

exposed to large forces from 

waves and fast-moving waters 

and may exacerbate scour at 

the building site.
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-7

COASTAL FOUNDATIONS AND BEST PRACTICES 6

Aswithanyfoundation,closedfoundationsmustadequatelysupportthestructureaboveandtransferloads

actingontheelevatedbuildingandthefoundationtothesoilbelow.Innon-coastalenvironments,wind

(orseismic)andgravityloadstypicallydominateandcontrolfoundationdesign.Incoastalenvironments,

floodloadsmustalsobeaddressed.

Windloadsaretransferredthroughastructureviaproperlydesignedandconstructedverticaland

horizontalloadpaths.Particularattentionshouldbegivenwherethebuildingattachestothefoundation;

theloadscreatedbythewindactingontheroof andwallsmustbetransferredthroughthebuilding

intothefoundationandintotheground.Forresidentialconstruction,connectionstoresistupliftand

shearwallreactionsfromwindforcesaredetailedinprescriptivecodesandstandardssuchasthe

IRC,AF&PAsWoodFrameConstructionManual,andICC-600,StandardforResidentialConstructioninHighWind

Regions.

Foundationsdesignedforwindonlymaylackthestrengthrequiredtoresistfloodloads.Whilewindresistant

foundationdesignsareprevalent,prescriptiveflood-andwind-resistantdesignsarelessavailable.

FEMA550isaguidancedocumentwhichpresentsmanywind-andflood-resistantdesigns.

Forshortfoundationwalls(i.e.,those3feethighorless)thatdonotretainbackfilledsoils,reinforcement

maybenecessaryinorderconstructafoundationwall.Itshouldbeconsideredthatthereinforcing

necessarytoresista1.5-foot-highbreakingwaveiscomparabletothatrequiredtoresistwindloadsof 120

mph.However,tallerfoundationwallsneedadditionalreinforcementtoresistbreaking-waveloads.For

example,8-foot-highwallsmayrequiretheplacementof verticalreinforcingsteelwithinmasonrywalls,

withaspacingof 16inchesoncenter.FEMA550containsdesignsforclosedfoundationsthatcanresist

windloadsandfloodloadsfrom1.5-foot-highbreakingwaves.

6.4.2.1 Crawlspace Foundations

Crawlspacefoundationstypicallyconsistof perimetermasonryorconcretefoundationwallsandasystem

of interiorbeamsandpiersthatsupportanelevatedfloorframingsystem.Inpermanentwoodfoundations,

theperimeterwallsareframedwithpreservative-treatedwoodframingandsheathing.Elevatedfloors

aretypicallywood-framed,buttheymayalsobeconstructedof concrete.Thissectiondiscusses

crawlspacefoundationsonclosedfoundationwalls.(SeeSubsection6.4.3.2foradiscussiononopen

crawlspacefoundations.)

Inmanyinstances,crawlspacesareusedasalocationformechanicalequipment(suchasductworkand

piping),andthefloorframingistypicallyconstructedof wood.If mechanicalequipmentisinstalledinthe

crawlspace,precautionsshouldbetakeninordertomakesurethattheductworkislocatedabovetheBFE

inordertomaintainNFIPcompliance.

Closed-wallcrawlspacefoundationsareusuallyconstructedonrelativelyshallow,cast-in-placeconcrete

footings,wherethedepthof thefootingisdictatedbythelocalfrostdepth.Becauseclosed-wallcrawlspace

foundationsareshallow,theyarevulnerabletobeingunderminedfromerosionandscourandarenot

recommendedforusewithinCoastalAZones.Becauseclosed-wallcrawlspacefoundationsarevulnerable

tobreakingwaves,theNFIPprohibitstheirusewithinVZones.Figures6-5and6-6illustratethe

vulnerabilityof closed-wallcrawlspacefoundationswithinaVZone.
6-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

TheNFIPrequiresfloodopeningsincrawlspacefoundationsconstructedwithinSFHAs.Aminimum

of twoopenings(havingatotalnetareaof notlessthan1squareinchforeachsquarefootof enclosed

areasubjecttoflooding)shallbeprovided.Toremaineffective,theNFIPrequiresthatthebottomsof 

floodopeningsbeplacedwithin1footof grade;thislimitslateralforcesonfoundationwalls.(FEMA

499TechnicalFactSheetsNo.15,FoundationWalls,andNo.27,EnclosuresandBreakawayWalls,contain

guidanceonfloodopenings.)

Figure 6-5.

Building failure caused by 

undermining of crawlspace 

foundation during Hurricane 

Fran. Breaking waves may also 

have contributed to foundation 

failure. (Source: FEMA 290)

Figure 6-6.

Failure of crawlspace foundation 

undermined by scour.

(Source: FEMA 290)
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-9

COASTAL FOUNDATIONS AND BEST PRACTICES 6

Floodopeningscanrarely,if ever,beusedforairventilationand

humiditycontrol.Ventsforhumiditycontrolaretypicallymost

effectiveatpreventingcondensationonvulnerablefloorframingwhen

theyareinstalledhighwithinthecrawlspace;suchplacementisnot

effectiveforprotectingfoundationwallsfromdamagingfloodloads.

Ventswithcombinedpurposesshouldbeinspectedtoverifytheir

properpositioning.

Arecenttrendinvolvestheuseof conditionedcrawlspacesfortemperatureandhumiditycontrol.To

proveeffective(andtoavoidexacerbatingmoistureproblems),crawlspacesmustbecompletelysealedto

preventmigrationof exteriorhumidityintothespace.Theymustalsobeinsulatedtocontrolcoldareas,

wherecondensationcanform.Properlyconditioningcrawlspacesisacomplexundertaking.Becausethey

mustbecompletelysealedforeffectiveconditioning,conditionedcrawlspacesshouldnotbeusedwithin

SFHAsunlesstheNFIP-requiredfloodventsadequatelysealthespacewhileremainingabletoopen

underthepressureexertedbyfloodwaters.Also,theNFIPrequiresthatanymaterialplacedbelowthe

BFE(orDFE)beflood-resistant,thusprecludingtheuseof manytypesof insulation.

6.4.2.2 Stem Wall Foundations 

Stemwallfoundationsaresimilartocrawlspacefoundations.Theyconsistof perimeterfoundation

walls(typicallymasonryorconcrete),buttheinteriorspacethatwouldotherwiseformthecrawlspace

isbackfilledwithsoilsthatsupportafloorslab.IntheGulf Coastregion,thesefoundationsareoften

referredtoaschainwalls.Figure6-7showsacrosssectionof atypicalstemwallfoundation.

Anecdotalevidencesuggeststhatduringfloodeventsstemwallfoundationshaveperformedbetterthan

manycrawlspacefoundations.However,itisimportanttonotethattheprescriptivedesignssetforthin

thebuildingcodesoftenlimitstemwallheighttojustafewfeet.Whilehigherstemwallfoundationscan

bedesigned,thecostof suitablefillandproperfillplacementoftenmakestheiruseimpractical.Theuse

of stemwallfoundationsisprohibitedwithinVZonesandisnotrecommendedforusewithinCoastalA

Zones;however,theiruseisappropriatewithinAZoneswherewaveheightsare1.5feetorlessandwhere

footingsaredeepenoughtoresistscouranderosion.

Stemwallfoundationsdonotrequireventstoequalizethepressuresexhibitedbyfloodwaters.Theydo,

however,needtobestrongenoughtoresistlateralpressurefromretainedsoils.Becausetheretainedsoils

canbecomesaturatedduringafloodevent,additionalreinforcementistypicallyneeded.

FEMA550hasprescriptiveflood-andwind-resistantdesignsforstemwallfoundations.Designsare

providedfortwotypesof walls:cantileveredandlaterallysupported.Incantileveredwalls,reinforcing

steelprovidessufficientstrengthtoresistlateralforceswithoutrelyingonthefloorslabtolaterallysupport

thetopof thewall.Inlaterallysupportedwalls,thetopof thewallistiedtothefloorslab;thetypical

resultisthatlessverticalreinforcementisneededinthefoundation.Laterallysupportedwallsmustbe

bracedtopreventmovementorcollapsewhenbackfilling.

NOTE

FEMA 550 has prescriptive 

designs for crawlspace 

foundations up to 8 feet high 

for Exposure C design-wind 

speeds of up to 150 mph. 
6-10 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

6.4.2.3 Slab-on-Grade Foundations 

Slab-on-gradefoundationsaresimilartostemwallfoundations.Likestemwallfoundations,thefloor

consistsof aconcrete-gradeslab.Unlikestemwallfoundations,however,slab-on-gradefoundationsdo

nothaveatrueperimeterfoundationwall,butinsteadhavethickenedportionsof theslabthatfunction

asfootersfortheexteriorwallsandinteriorbearingwalls.

Inmanyareas,slab-on-gradefoundationsarethemostcost-effectivetypeof foundation.InanSFHA,

however,theirusecarrieslimitations.Fromapracticalstandpoint,theycanonlybeusedtoelevatea

building1footorless(higherelevationsrequirelargequantitiesof concrete).Therefore,whereflood

depthsexceed1foot,theuseof otherfoundationsshouldbeconsidered.Slab-on-gradefoundationscan

beusedinconjunctionwithproperlyplacedandcompactedfill.

Slab-on-gradefoundationsareshallowfoundationsthataresusceptibletobeingunderminedbyscour

anderosion.Theuseof slab-on-gradefoundationsisprohibitedwithinVZonesandisnotrecommended

forCoastalAZones.(NotethatparkingslabsareoftenpermittedbelowelevatedbuildingsinVZones,

buttheyarerecommendedtobefrangible;bytheirdesignrequirements,theyarethemselvessusceptible

tounderminingandcollapse.)

Compacted Soil

or Fill

Concrete Slab on Fill

Exterior Wall

Footing Depth per

Building Code

Backfill

Figure 6-7.

Typical stem wall foundation.

(Source: FEMA 543)
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-11

COASTAL FOUNDATIONS AND BEST PRACTICES 6

6.4.3 Open Foundations

Openfoundationsareconstructedinsuchamannertoallowfloodwaterstoflowfreelythroughthem.

Openfoundationsalsominimizethetotalsurfaceareathatfloodwatersmayactupon.Whencompared

toclosedfoundationsforthesamesizebuilding,anopenfoundationwillhavelower-magnitudeflood

forcesactingonthefoundation.Openfoundationsalsoofferthebenefitof beinglesssusceptible

todamagefromfloodbornedebrisbecausetheyprovidelesscontactareafordebristoimpactthan

closedfoundations.

Simplystated,theportionof thefoundationaboveexteriorgradeisminimalandallowsnearlyunrestricted

movementof floodwatersbeneaththebuilding.Below-gradefoundationcomponentscanbedescribed

asadeepfoundationwithdeeplydrivenpiersorcaissonsorshallowfoundationswithfootingsorgrade

beams.Termssuchasdeepandshallowarerelativeandarebestusedtorefertothemaximumscour

anderosionanticipatedduringadesigneventorduringtheprojectedlifeof thebuilding.

Figure 6-8.

FORT MYERS BEACH, FLORIDA: 

Oceanfront house constructed 

on an open foundation sustained 

only minor damage after being 

exposed to high winds and storm 

surge. (Source: FEMA 488)

NOTE

While Hurricane Charley

created near design-level winds 

in Florida, the storm surge 

created by the hurricane was 

limited. As a result, it was not 

a design flood event in most 

impacted areas.
6-12 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

6.4.3.1 Deep, Open Foundations

Buildingsfoundedandsupportedbydrivenpilesorcaissonsindeepsoilstratagenerallyofferthegreatest

resistancetocoastalhazards.Whensupportedbyfoundationsdeepenoughtoretainsufficientstrengthto

resistfloodloadsafterscouranderosionhaveremovedsoilsaroundthefoundation,properlyconstructed

buildingscanfarewell,evenwhenexposedtowindloads.Post-eventassessmentshaverevealedsuccess

stories,evenwhenbuildingshavebeenexposedtoconditionsgreaterthanthoseanticipatedduringa

designevent.Figures6-9and6-10illustratethesuccessfuluseof deep,openfoundations.

Figure 6-9.

FORT MYERS BEACH, FLORIDA: 

Newly constructed house elevated 

on an open foundation sustained no 

storm surge damage when surges 

several feet deep impacted this 

site in 2004. (Source: FEMA 488)
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-13

COASTAL FOUNDATIONS AND BEST PRACTICES 6

Unfortunately,post-eventassessmentsof buildingsondeepfoundationsincoastalareasoftenreveal

failuresduetopoorconstruction.Manyof thesefailuresresultfromtheuseof inadequatelydesigned

foundationsorinadequateconnectionsbetweentheelevatedstructureanditsfoundation,asshownin

Figures6-11and6-12.

Figure 6-10.

DAUPHIN ISLAND, ALABAMA: 

Successful pile foundation following 

Hurricane Katrina. The foundation 

supported the elevated home even 

after scour and erosion removed 

several feet of soils. 

(Source: FEMA 549)

Figure 6-11.

DAUPHIN ISLAND, ALABAMA: 

Structure near collapse due to 

insufficient pile embedment. 

(Source: FEMA 549)
6-14 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

Forsuccessfulperformance,deepandopenfoundationsmustbedesignedtoelevatethebuildingabove

anticipatedfloodwaters,transferallloadsappliedtotheelevatedbuildingandtheexposedfoundation

componentstothesupportingsoils,andresistthedamagingeffectsof breakingwaves,movingfloodwaters,

andfloodbornedebris.FEMA55andASCE24-05providedetaileddesignprocedurestocalculatethe

loadsassociatedwiththesecriteria.Noprescriptivesolutionsforopenfoundationsareprovidedineither

theIBCortheIRC.

Pilefoundationsconsistof deepverticalpilesinstalledtosupportanelevatedstructure.Becausepile

foundationsaretypicallysetdeepwithinthesoil,theyareinherentlylesssusceptibletoscouranderosion.

Pilesrelyprimarilyonthefrictionforcesthatdevelopbetweenthepileandthesurroundingsoils(toresist

gravityandupliftforces)andonthecompressivestrengthof thesoils(toresistlateralmovementand

maintainthestructureslateralstability).Thesoilsattheendsof thepilesalsohelpresistgravityloads.

Whenthepilesrestontheirpiletipsforloadbearing,thedesignermustshowthatthesoilsurroundingthe

pilesprovidesappropriatelateralstability.Seriousconsiderationshouldbegivenbythedesignertoensure

thatthestructureiscapableof maintainingitslateralstabilityduringastormevent.

Severalstylesof deep,openfoundationsexist.Pilesaretypicallytreatedwoodtimbers,steelpipes,orprecast

concretemembers.Othermaterials,suchasfiber-reinforcedpolyester(FRP),areavailablebutare

notcommonlyusedinresidentialconstruction.Forloadpathcontinuity,considerationshouldbegivento

extendingthetimberpilestotheroof level(insingle-storybuildings)ortothesecondlevel(inmulti-level

buildings).Thisprovidesadditionalstiffnesstothestructurethatreducesundesirabledeflectioninthe

building,increasestheabilityof abuildingtoresistlateralloads,andmayreducetheneedtocross-brace

thepiles.

Crucialaspectsof apilefoundationincludepilesize,installationmethod,embedmentdepth,bracing,

andconnectionstotheelevatedstructure(seeFEMA,499TechnicalFactSheetsNo.12,PileInstallation,

andNo.13,Wood-Pile-to-BeamConnections).Inadequateembedmentandtheuseof improperly-sizedpiles

greatlyincreasetheprobabilityof structuralcollapse.Pilesareappropriateforusewithinallcoastalzones

whenthebearingandlateralcapacitiesareverifiedbyageotechnicalengineer.

Figure 6-12.

LONG BEACH, MISSISSIPPI: 

Structure removed from its 

foundation when waves exceeded 

the foundation height and 

connections between the elevated 

building and its foundation failed. 

The building was located within a 

mapped V Zone. 

(Source: FEMA 549)
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-15

COASTAL FOUNDATIONS AND BEST PRACTICES 6

Themethodof installationisamajorconsiderationinthestructuralintegrityof pilefoundations.The

idealoptionistouseadriven-pilemethod,asitdisturbsthesupportingsoilaroundthepiletheleast

amountandresultsinthehighestbearingcapacityforeachpile.Throughthismethod,thepileisheldin

placewithleadswhileasingle-actingordouble-actingdiesel-orair-poweredhammerdrivesthepileinto

theground(seeFigure6-13).

Driven

Hammer to

Set in Place

Hammer to

Set in Place

Water Injected to

Create Hole for Pile

Augered

Hole

Hammer

(or vibratory

hammer)

Drives Pile

Augered Jetted

Figure 6-13.

Pile installation methods.

(Source: FEMA 55)

Drivenpilesmaybesetwithvibratoryhammersorwithdrophammers,withdrophammerstypically

provingtobethelessexpensivechoice.Adrophammerconsistsof aheavyweightraisedbyacable

(attachedtoapower-drivenwinch)whichisthendroppedontothepile.

If steelpilesareemployed,onlythedriven-pilemethodshouldbeused.Foranypiledriving,theauthority

havingjurisdictionortheengineer-of-recordmayrequirethatadrivinglogismaintainedforeachpile.

Thelogwillrecordthenumberof blowsrequiredperfootasdrivingprogresses.Thislogisakeyfactor

usedtodeterminepilecapacity.

Holesforpilesmaybeexcavatedbyanaugerif cohesivesoilswithsufficientclayorsiltcontentare

presenttopreventcave-in.Augeringcanbeusedaloneorinconjunctionwithpiledriving.If theholeis

full-sized,thepileisdroppedinandthevoidbackfilled.Alternatively,anundersizedholecanbedrilled

andapiledrivenintoit.Whensoilconditionsareappropriate,theholewillstayopenlongenoughto

dropordriveinapile.

Jettingisanotherfrequentlyusedmethodof insertingpilesintosandysoil.Jettinginvolvesforcingahighpressure

streamof waterthroughapipethatadvanceswiththepile.Thewatercreatesaholeinthesand

asthepileisdrivenuntiltherequireddepthisreached.Unfortunately,jettingloosensthesoilthatwill

supportthepileandthetip,resultinginalowerloadcapacityduetolessfrictionalresistance.Figure6-13

showsvariousmethodsof pileplacement.
6-16 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

Wood-Pile-to-BeamConnections

Woodpilesareusedinmanycoastalareasforopenfoundation.Thesepilesareoftennotchedtoprovide

abearingsurfaceforabeamsupportingthehouseabove.Whenthismethodisused,thenotchshouldnot

reducethepilecrosssectionmorethan50percent(suchinformationistypicallyprovidedbyadesigner

onthebuildingplans).Alargerpilenotchthan50percentwillresultinareducedcapacitytocarrylateral

loadsattheconnection.Also,forpropersupportof verticalloads,thebeamshouldbearonthesurface

of thepilenotch.

Chapter5discussedtheimportanceof connectionswithinthecontinuousloadpath.Post-disaster

investigationshaveobservedthatthewood-pile-to-beamconnectionpointhasbeenacriticallink.If 

thereisapoorconnectionatthepointwherethetopof thepileconnectstothebuildingitself,failure

mayoccur.Anengineershoulddesigntheconnectionbetweenawoodpileandtheelevatedstructure(see

FEMA499,TechnicalFactSheetNo.13,Wood-Pile-to-BeamConnections).Thisconnectionmayrequirepile

bracinginordertoreduceapilesunbracedlengthandmaintainastrongconnection.Engineersshould

considerthepilegroup,theconnections,andthefloorsystem(diaphragm)asanentiresystem.Inorder

toeliminatepileandconnectionfailures,itisimportantthatthefloorsystemandthepilegroupactasa

completesystemandnotindependently.

PileBracing

Whilefoundationdesignsthatarefreeof bracingarepreferred,mostfoundationdesignsusingtimber

pilesrelyuponbracing.Possibleexceptionsincludeshort-pilefoundations(i.e.,thoseextendingbetween

4and6feetabovegrade),foundationssupportingsmallhomeswithlimitedverticalsurfacesexposed

towindloads,orfoundationsinareaswithlowbasicwindspeeds.Wheninstalledproperly,bracing

increasesthestiffnessof thepilegroupthat(insomecases)mayallowforwiderspacingof pilesbeneath

thebuildingorsmallerdiameterpilestobeused.Theinclusionof bracingincreasestheaxialcapacityof 

atimberpileduetothereductioninunbracedlength.Bracingalsoreduceslateraldisplacementsof the

buildingbystiffeningthefoundation.

Inwood-framedconstruction,bracingtypicallyinvolvesdiagonalcross-bracingorknee-bracing.Diagonal

cross-bracingconsistsof long,slendersteelrodsordimensionallumberinstalleddiagonallybetween

adjacentpiles.Kneebracesareshortermembersinstalledbetweenpilesandthebeamstheysupport.

Kneebracesextendfromtheupperportionof thepiletothebeamsandsupportthepileinsucha

mannerthattheunbracedlengthof thepileiseffectivelyreducedwhileallowingthefloorsystemtobe

elevatedashighaspossible.Duetothestrengthlimitationsinherentinwoodframing,however,someof 

theproperconnectionsrequiredtotransfertheloadsaredifficulttoobtainwithwoodframing.

Diagonalcross-bracingisthemosteffectivemeansof bracingapiletoreducetheunbracedpilelength,

butthismethodhasvulnerabilitieswhenusedincoastalfoundationapplications.Thebracesthemselves

canobstructmovingfloodwaterandincreaseafoundationsexposuretoimpactfromwavesanddebris

(seeFigure6-14).Knee-bracingislessvulnerabletofloodloadsanddebrisimpactbutmaynotprovideas

muchstabilityandsupportasdiagonalcross-bracing.

Becausediagonalbracestendtobeslender,thesemembersaresusceptibletocompressionfailures;hence,

mostbracingisconsideredtension-onlybracing.Becausewindloadsand(toalesserextent)floodloads
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-17

COASTAL FOUNDATIONS AND BEST PRACTICES 6

canactinoppositedirections,tension-onlybracingmustbeinstalledinpairs.Onesetof bracesresists

loadsfromonedirectionwhilethesecondsetresistsloadsfromtheoppositedirection.

Figure6-14showshowtension-onlybracingpairsresistlateralloadsonastructure.Theorientationof 

thebracingisanimportantdesignconsiderationanditisimportantthatthebracingisconstructedina

mannerconsistentwiththeplans.Bracingshouldbeorientedparalleltotheanticipateddirectionof the

flowof watertoreducethepotentialfordebrisdams.

Theplacementof theboltedconnectionof thediagonalcrossbracetothepilerequiresconsiderable

judgment.If theconnectionisplacedtoohighabovegrade,thepilelengthbelowtheconnectionisnot

bracedandtheoverallbracingwillprovelessstrongandsturdy.If theconnectionisplacedtoocloseto

grade,theboltholeismorelikelytobefloodedorinfestedwithtermites.Becausetheboltholepasses

throughtheuntreatedpartof thepile,floodingandsubsequentdecayortermiteinfestationmayweaken

thepileatavulnerablelocation.Theboltholeshould,therefore,betreatedwithapreservativeafter

drillingandbeforeboltplacement.Knotsandotherimperfectionsinthepileandbracingshouldalso

beconsideredwhenselectingtheconnectionpoints.ItisimportanttoreviewSectionsR319,R320,and

Typical

Brace Pairs

Lateral Forces

Braces loaded in tension (T) resist 

lateral force (F). Braces loaded in

compression (C) are not effective.

Forces in opposite direction

bring opposite braces into play.

Figure 6-14.

Diagonal bracing schematic. (Source: FEMA 550)
6-18 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

R402.1.2of theIRCtomakesurethatoncetimberpilesarenotchedandbolted,thepilesareproperly

field-treatedtoresistdecayandtermiteinfestation.

Theuseof kneebraces(seeFigure6-15)involvesinstallingshortdiagonalbracesbetweentheupper

portionsof thepilingsandthefloorsystemof theelevatedstructure.Thebracesincreasethestiffnessof 

anelevatedpilefoundationandcanbeeffectiveatreducingthelateralforcesonahome.Whilekneebraces

donotstiffenafoundationasmuchasdiagonalbracing,theydooffersomeadvantagesoverdiagonal

braces.Forexample,kneebracespresentlessobstructiontowavesanddebris,areshorterthandiagonal

braces,andareusuallydesignedforbothtensionandcompressionloads.Unlikediagonalbraces,knee

bracesdonotreducebendingstresseswithinthepiles(infact,kneebracescanactuallyincreasebending

stresses)andwillnotreducethediameterof thepilesrequiredtoresistlateralloads.

Beam

Knee Brace

Approximately 4’ 

(follow design)

*Knee braces of this type can also be used on 

 notched round piles.

7D Minimum

D = Bolt diameter

Countersunk through-bolts

or lag screws per design

Knee brace connection on square pile*

Figure 6-15.

Knee brace connection example. 

(Source: FEMA 550)

Theentireloadpathintoandthroughthekneebracemustbedesignedwithsufficientcapacity.The

connectionsateachendof eachkneebracemustpossesssufficientcapacitytohandlebothtensionand

compressionandtoresistverticalloadsinthebrace.Thebraceitself musthaveasufficientcross-sectional

areatoresistcompressionandtensileloads.

GradeBeamsinPile/ColumnFoundations

Thetermgradebeamisusedinavarietyof waystodescribeanumberof foundationelements.Themost

commonuseininlandconstructionreferstoaspreadfooting,whichallowsafoundationtouniformly

distributetheloadoverareasof soilwithreducedbearingcapacity.However,incoastalareas,theterm

gradebeamoftenreferstoaconstructiontechniqueutilizingasystemof concretepoursthathelptofixthe

locationsof pilesandthusmitigatesomefloodloads.
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-19

COASTAL FOUNDATIONS AND BEST PRACTICES 6

Pilefoundations(seeFigure6-16)maybedesignedwithgradebeams(typicallyfromwoodorconcrete).

Gradebeamsprovidemanybenefits:

n When

incorporatedwithreinforcedconcreteormasonrycolumnfoundationsystems(orwith

woodpiles),gradebeamsprovidelateralstiffnesstopreventtheneedfordiagonalcross-bracingor

knee-bracing.

n Properly

designedandconstructed,gradebeamsfacilitateloadredistributionandcanreducethe

potentialforcollapseduringextremeevents.

n Grade

beamscanallowbuilderstoaccommodatetheinevitablevariationsthatalwaysseemtoaffect

pileplacement.

Toreducetheeffectof scouranderosiononfoundations,gradebeamsmustbedesignedtobeselfsupporting

foundationelements;thatis,gradebeamsmustnotrelyuponthesoilsbeneaththemfor

verticalsupport.Also,thepilesmustbedesignedtocarrytheweightof gradebeamsinordertoaddress

theconditionthatresultswhengradebeamsareunderminedbyscourorerosion,inadditiontoresisting

allloadstransferredtothepilesfromtheelevatedstructureandthefoundation.Forthisreason,itis

importanttoensurethatotherbuildingelementsarenotconnectedtothepiles.Slabsusedbelowpileelevated

homesshouldnotbeconnectedtopilefoundationsorusedasgradebeams.If theslabisdamaged

Figure 6-16.

Elevation view (right) of a concrete pile foundation using grade beams. (Source: FEMA 550) 
6-20 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

orundermined,theslabmaybeexposedtofloodforcesandtransferloadstothefoundation.Inmost

cases,thefoundationwasnotdesignedtoresistthesehigherloadsandthefoundationmaybeoverloaded,

causingittofail.

Consensuscodesandstandardsgenerallydonotcontainprescriptivedesignsforopenfoundations;

however,criteriaareprovidedforperformance-baseddesign.Section303.4of SSTD-10requiresthat

wood-pilefoundations,theirbeams,andconnectionsbetweenthebeamsandthepilesmustbedesigned

byaregisteredengineerorarchitect.IRCSectionR324.2requiresthatfoundationsinVZonesbeopen

(placedoncolumnsorpilings).IRCSectionR324.3.3alsorequiresthatfoundationsinVZonesbe

designedtoresistwaterloadsassociatedwithfloodingandprecludestheuseof shallow(matorraft)

foundationsinareaswhereerosioncanunderminefoundations.Nocodeorindustrystandardcurrently

providesprescriptivedesignsforopenfoundations.FEMA550providesguidanceforengineersand

architectswhodesignfoundationsforcoastalsites,aswellasprescriptivedesignsforawiderangeof 

buildingsandfoundationstyles.

BreakawayWalls

WithintheSFHA,wallsmaybeusedtoenclosetheareabelowthelowestfloor,butthesecreateacondition

whichmustbeaddressed.Thewallsorenclosuremayconsistof latticework,insectscreening,orwalls

specificallydesignedtofailorbreakawayunderwaterorwindloadswithoutcausingstructuraldamage

totherestof thestructure.Itisimportantthatthesewallsbeconstructedwithflood-resistantmaterials.

Theyaredesignedtobreakfreewithloadsof notlessthan10poundspersquarefootbutnotmorethan

20poundspersquarefoottopreventtheirloadingfromimpartingadditionallateralloadsonstructural

members.Thesewallsaretypicallyconstructedof woodstudswithanexteriorsheathing,buttheymay

beconstructedof unreinforcedmasonryunitsanddesignedtofailatthemortarjoints.

Akeyfeatureof asuccessfulbreakawaywallisthattheexteriorsheathingdoesnotoverlapthestructures

pilingorverticalmembers.Additionally,itmaynotoverlapthelowesthorizontalstructuralmember

orabovethat.Thesedesignfeaturesensurethatthewallfailuredoesnotimpactthemainstructure.

Breakawaywallsshouldbecertifiedbyaprofessionalengineerorarchitectandtheproperdocumentation

submittedwiththebuildingpermit.(SeeFEMANFIPTechnicalBulletin9:DesignandConstructionGuidance

forBreakawayWallsBelowElevatedCoastalBuildings(FIA-TB-9),forfurtherinformation.)SeeFigure6-17

foranexampleof thesuccessfuluseof abreakawaywallandFigure6-18,whichdemonstratesbuilding

damagesduetoincorrectconstructionof abreakawaywall.

6.4.3.2 Shallow, Open Foundations

Shallow,openfoundationsgenerallyconsistof concreteormasonrypiersplacedonconcretefooters.

Theiropenstylemakestheirusedesirableinareaswherebreakingwavesmayexist.Becausetheyare

foundedonshallowsoils,however,theyremainvulnerabletoscouranderosion.

Shallow,openfoundationsmaybeallowed,buttheirusemaynotbesuitableforVZones(seeFigure

6-19).If ashallow,openfoundationcanbeunderminedbyscourorerosion,thefoundationwouldnot

satisfytheNFIPrequirementof preventingcollapse.Thesefoundationsaremoresuitableforusewithin

CoastalAZones,wherethepresenceof erosionandscourislimited.Shallow,openfoundationsmaybe

usedwithinCoastalAZonesif thetopsof theirfootingscanbeplacedbelowthemaximumscourand
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-21

COASTAL FOUNDATIONS AND BEST PRACTICES 6

Figure 6-17.

Successful use of 

a breakaway wall. 

(Source: FEMA 489)

Figure 6-18.

Building damages due to 

the incorrect construction 

of a breakaway wall.

(Source: FEMA 489) 
6-22 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

erosionlevelsanticipatedforthelifeof thestructure.Thetopsof thefootingsshouldbepositionedbelow

themaximumanticipatedscourorerosiondepthbecauseanyuncoveredareaof afootingwillbeexposed

tofloodforces.Also,anyuncoveredareaof afootingactsasanobstructiontomovingfloodwatersand

willcontributetolocalizedscour.Inallapplications(whetherinlandorcoastal),frost-depthrequirements

mustbeconsidered,astheymaydictatethedepthatwhichthetopof thesefootingsisset.Whereexpected

erosionandscourcannotbeaccuratelyquantified,deepandopenfoundations(suchaspilings)should

beused.

Theperformanceof shallow,openfoundationsdependslargelyuponthestyleof footingusedtosupport

concreteormasonrypiers.Discretepad-stylefootingsrelyonlyupontheweightof theelevatedstructure

andthesoil-bearingcapacitytoresistoverturning.Whenexposedtolateralloadsorwhenunderminedby

erosionorscour,discretefootingscanrotate.Therefore,piersplacedondiscretefootingsareconsidered

toreflectbestpracticesonlywhenwindandfloodloadsarerelativelylow.Post-disasterinvestigationshave

revealedthatadiscretefootingmayfailwhenabuildingisexposedtolateralloads,evenwhenitisnot

underminedbyscouranderosion(seeFigures6-20and6-21).

Adesiredalternativetodiscretepadfootingsistoconstructamatrixof gradebeams.Piersplacedon

continuousconcrete-gradebeamsorconcretestripfootingsprovidemuchgreaterresistancetolateral

loadsbecausethegradebeams/footingsactasanintegralunitandarelesspronetorotation.

Figure 6-19.

Possible failure modes for masonry piers. (Source: FEMA 550)

Pier Pier Pier

Overturning Used only where the potential

for erosion and scour is low or 

where the pier can be 

anchored to underlying

bedrock or other stratum that

terminates erosion and scour

Used where the potential

for erosion and scour is high

Maximum

depth of erosion

 and scour

Maximum

depth of 

erosion

 and scour

Uplift Erosion
FEDERAL EMERGENCY MANAGEMENT AGENCY 6-23

COASTAL FOUNDATIONS AND BEST PRACTICES 6

Footingsandgradebeamsmustbereinforcedtoresistthebendingmomentsthatdevelopatthebaseof 

thepiersduetothelateralloadsonthefoundationandtheelevatedhome(seeFigure6-20).Lateralflood

andwindforcesresultindetailingandconnection/reinforcementrequirementsthataremoresignificant

androbustthanthosecommonlyusedforinlandconstruction.Theuseof minimalreinforcement

orsmallconnectorsshouldbequestionedastotheiradequacyincoastalapplications/foundations

(seeFigure6-21).

AlthoughtheIRCprovidesprescriptivesolutionsthatmaybeusedfordesigningthebuildingabovethe

foundation,theIRCdoesnotprovideprescriptivedesignsforopenfoundations.FEMA550contains

guidanceforengineersandarchitectswhodesignfoundationsforcoastalsites.FEMA550alsooffers

prescriptivedesignsforawiderangeof buildingsandfoundationstyles.AddendumCof ICC-600

(releasedinSeptember2008)includessomeprescriptivedesignsforopenfoundation.Theaddendum

hasprescribedbeamdesignsthatcanbeusedinconjunctionwithFEMA550foundationdesigns.

Figure 6-20.

PASS CHRISTIAN, MISSISSIPPI: 

Performance comparison of 

shallow, open foundations founded 

on discrete footings (foreground) 

failed by rotating and overturning, 

while piers located on more 

substantial footings—in this case, 

a concrete mat (background)—

survived. (Source: FEMA 549)

Figure 6-21.

BELLE FONTAINE POINT, 

JACKSON COUNTY, MISSISSIPPI: 

Column connection failure. 

(Source: FEMA 549)
6-24 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

6 COASTAL FOUNDATIONS AND BEST PRACTICES

6.5 Soils Investigation

Thefoundationdesignchosenshouldbebaseduponthesoilsthatexistatthebuildingsite.TheIBCand

IRCrequiresoil-bearingcapacitiesthatareidentifiedinIRCSectionR401.4andIBCSection1802,

respectively.Soilparameterscanbedeterminedfromthefollowing:

n Soil

samplesfromboringsortestpitsonthesite

n A

reviewof boringsfromnearbysites

n Information

fromthelocalofficeof theNaturalResourcesConservationService(formerlyknownas

theSoilConservationService)andsoilsurveyspublishedforeachcounty

n The

typesof foundationsthathavebeeninstalledwithintheareainthepast

n The

proposedsitehistory,whichwouldindicatethepresenceof buriedmaterials(Thismayrequire

asearchof landrecordsshowingpastownershipfocusedonhowthesitemayhavebeenusedin

thepast.)

Oneof theparametersderivedfromasoilinvestigationisthebearingcapacity,whichmeasurestheability

of soilstosupportgravityloadswithoutsoilshearfailureorexcessivesettlement.Commonlymeasuredin

poundspersquarefoot(psf),soil-bearingcapacitytypicallyrangesfrom1,000psf forrelativelyweaksoils

tomorethan10,000psf forbedrock.

Frequently,designsareinitiallypreparedaccordingtoapresumedbearingcapacity.Itisthenthe

homebuildersresponsibilitytoverifyactualsiteconditions.Theactualsoil-bearingcapacityshouldbe

determined.If soilsarefoundtohavehigherbearingcapacity,thefoundationcanbeconstructedas

designedoritcanberevisedtotakeadvantageof thesebettersoils.

Theallowableload-bearingvaluesof soilsspecifiedinIBCSection1804canbeusedwhenotherdata

arenotavailable.However,soilscanvarysignificantlyinbearingcapacityfromsitetosite.Ageotechnical

engineershouldbeconsultedwhenunusualorunknownsoilconditionsareencountered.

Thelateralcapacityof thesoilshouldnotbeoverlooked.Buildingfailureduetoalackof lateralsoil

capacityiscommonduringstormevents.Inadditiontoverifyingthebearingcapacityof thesoilatthe

site,thesoilslateralcapacityshouldbeconsistentwiththepresumedlateralcapacityinthebuilding

plans.Intheeventthatthesoillateralcapacitydoesnotmeetthedesigncapacityof thefoundation,the

buildingfoundationwillneedtobemodifiedinordertoaccountforsiteconditions.
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-1

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

Building Framing Systems 

and Best Practices

7.1 Introduction

T

heimportanceofproperlydesignedfoundationswasdiscussedinChapter6,CoastalFoundations

andBestPractices.Inthischapter,theimportanceofbuildingframingsystemsisdiscussed.

Abuildingsframingworksinconjunctionwithitsfoundationtoprovidestrengthandstabilityfor

thestructure;itisalsoanothercriticalcomponentof theloadpath.Properlydesignedandconstructed

buildingframingisimportantinalllocations;however,incoastalareas(wherewind,flood,andother

loadscanbeextreme),ensuringproperbuildingframingiscritical.

Framingmusttransferallgravity,uplift,andlateralloadstothefoundation.Inbuildings(including

residentialstructures),framingsystemstypicallyconsistof theroof structurethatsupportstheroof 

deck,exteriorandinteriorload-bearingwalls,beams,girders,posts,andfloorframing.Shearwalls(or

steelmomentframesinhomeswithlargewindowsorotherlargeopenings)providethestrengthto

resistlateralloads.

Theintegrityof theoverallbuildingdependsnotonlyuponthestrengthof thesecomponents,butalso

ontheadequacyof theconnectionsthatexistbetweenthem.Criticalconnectionsoccurthroughout

thestructurebut,inmosthouses,themostcriticalconnectionsexistwheretheroof systemconnectsto

supportingwalls;atopeningsandheadersinthewalls;wherewallsconnecttoeachotheratfloorlevels;

andwherewallsconnecttothefoundation.RefertoChapter5foradetaileddiscussiononthecontinuous

loadpathconceptandtheimportanceof connectionswithintheloadpath.

Whilethetermframingtypicallyreferstoeitherwoodorlight-gaugesteelframing,wallsconstructed

withconcreteormasonrysystemsarealsotypicallyusedtocarryloadsandtoactastheframeof the

building.Load-bearingwallsystemsof anyconstructiontypecanandshouldbeconsideredaspartof 

buildingframingdiscussions.Assuch,load-bearingwallsystemsarepresentedinthischapter.

Whilebuildingsareconstructedfromthegroundup,Chapter5identifiedhowtheyareoftenanalyzed

fromtheroof downinordertotrackthepresenceof acontinuousloadpath.Likewise,thisdiscussionon

buildingframingbeginswiththeroof-framingstructure.However,beforeconcentratingonroof framing,

abrief discussionof diaphragmsandshearwallsispresentedbecausetheyaretwoof thekeyelementsin

theframingof load-bearingwallsystemsinmostresidentialandlightcommercialconstruction.
7-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

7.2 Diaphragms and Shear Walls 

Mostresidentialandlightcommercialconstructionisbasedon

boxdesign.Inboxdesign,horizontaldiaphragms(e.g.,roof and

floorsystems)workinconjunctionwithverticalshearwallstosupport

gravityloads,resistlateralloads,andprovidestructuralstability.In

woodandlight-gaugesteel-framedconstruction,thediaphragms

andshearwalls(calledbracedwalllinesorbracedwallpanels

inmanycodesandstandards)areconstructedsimilarly.Bothuse

framingmembers(suchasdimensionallumber,engineeredlumber,

orlight-gaugeC-shapedsteelmembers)surfacedwithstructural

sheathing(typicallyplywoodorOSB).TheIRCandIBCprovideprescriptive,framed,shearwalldesigns

thatmaybeincorporatedintothebuildingdesigntoresistlateralloads.Theprescriptivedesignsspecify

requirementsforwallbracing,bracedwalllines,andbracedwallpanels.

Nearlyallhomeshaveexteriorshearwalls.Relativelylonghomes,largehomes,orhomeswithlarge

openingsintheexteriorwallsmayhaveinteriorshearwalls,aswell.Engineeredhomeswithlarge

windowordooropeningsmayusemomentframestoresistlateralloadsinadditiontoshearwalls.While

constructedsimilarly,diaphragmsandshearwallsactindifferentwaysastheybothworktotransferloads

downtothefoundationof thestructure.

Theedges(orends)of diaphragmsandshearwallsarecritical.Whendiaphragmsandshearwalls

areconnected,itiscriticalthatthisconnectionallowsloadstobepassedinordertoensurethatthese

componentswillfunctiontogetherasasystem.Figure7-1illustrateshowtheshearwalltransfersthe

Figure 7-1.

Load transfer between 

diaphragms and shear walls. 

DIAPHRAGM/SHEARWALL

INTERACTION

RESISTING FORCE

WIND LOADING

WIND LOADING

DIAPHRAGM

(Transfer lateral loads

to vertical [shear] wall)

SHEAR WALL

(Designed to resist a change

in shape due to loading)

DEFINITIONS

Shear Wall – Walls used in 

building construction that aid 

in transferring lateral loads from 

the roof system or walls down 

to the foundation.

Diaphragms – Either roof or floor 

systems that transfer lateral 

loads to the shear walls or to 

the foundation.
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-3

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

loadsappliedtotheroof throughthewallsanddownintothefoundationof thehouse.Thischapter

providesvaluableinformationthatexplainswhatisinvolvedincreatingaproperconnectioninthewall

andframingsystemsof coastalbuildings.

Whenwindforcesactonabuilding,transferringtheseinducedloadsthroughthehousewillrequire

connectionstotransfertheloadsintotheshearwallthroughbothcompression(pushing)andtension

(pulling).Itisimportantthatallof theelementsof thebuildingworktogetherinordertocreatethe

maximumamountof structuralstrengthandallowthebuildingtomaintainitsshapeandnotcompromise

thebuildingenvelope.Afailureintheconnectionoranyof thememberscouldresultinstructuralfailure.

Post-disasterinvestigationshaverepeatedlyobservedroof collapsesandwallfailuresthatarerepresentative

of theinabilitytoprovideaproperconnectionatthislocationintheloadpath.Figures7-2and7-3show

thedetailingrequiredinorderforthediaphragmsandshearwallstomaintaintheirrigidityandshapeso

thatproperconnectionsaremaintained.

Figure 7-3.

Vertical shear walls and 

shear wall components. 

BAND JOIST

SUPPORT

BEAM

HORIZONTAL DIAPHRAGM

SHEATHING

FLOOR

JOIST

FIGURE 7-2

SHEAR WALL

BAND

JOIST

BOTTOM PLATE

SHEAR WALL

HOLDDOWN

CONNECTOR

SHEAR WALL

HOLDDOWN

CONNECTOR

WALL STUDS

SHEATHING

FLOOR SUPPORT

BEAM UPLIFT

CONNECTOR

UPLIFT

CONNECTOR

DOUBLE BASE PLATE UPLIFT CONNECTOR CRIPPLE STUDS ROOF FRAMING

HEADER

JACK STUDS

Figure 7-2.

Horizontal diaphragm and 

diaphragm components. 
7-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

Manyof therequirementsinprescriptivecodesandstandardsareintendedtoensurethatbuildingsare

constructedwithadequatefloorandroof diaphragmsandshearwalls.Specifically,theIBC,IRC,WFCM,

andICC-600provideprescriptiveshearwalldetailsanddesignsthatmaybeappliedwhencertainbasic

conditionsaremet.Table2304.6of the2006IBCliststheminimumthicknessof wallsheathingand

maximumwall-studspacingforvarioustypesof woodenshear-wallapplications;TableR602.3(1)of the

IRCprescribesafastenerscheduleforwoodenstructuralmembersusedinwallconstruction.Similar

prescriptivemeasuresexistinothercodesandstandardsandvarywithmaterialtype.

7.3 Roof Construction

Post-disasterevaluationsof coastalbuildingsdamagedduringhigh-windeventshaveconsistentlyshown

thatstructuralfailuresoftenbeginwiththeroof.Windscanremoveroof coveringsfromtheroof sheathing,

tearroof sheathingfromsupportingframing(seeFigure7-4),andriproof framingfromsupportingwalls.

Thelossof roof coveringsandroof deckingcanallowwatertoenterabuildinganddamageordestroy

interiorfinishesandcontents,orevenworse,maydestabilizeastructureandleadtobuildingcollapse.

Thestructuralintegrityandsuccessfulperformanceof theroof structureduringhigh-windeventsdepends

upon:1)adequatelydesignedandspacedroof-framingmembers,2)adequatelateralbracingtosupport

roof framing,and3)adequateconnectionsbetweentheroof structureandthetopof thewalltocreatea

completeverticalloadpath.Theroof structure(consistingof theroof framing,roof decking/sheathing,

andanyinternalbracing)alsofunctionsasahorizontaldiaphragmandtransfersthehorizontalloads

imposedontheroof tothesupportingwallsbelow.

Roof failuresareoftenobservedonareasof thebuildingwherewindpressuresareconcentrated.These

areasincludethehigh-pressureeaveandcornerzones,porchandroof overhangs,gableends,andwhere

roof framingjoinsbearingwallsorbeams.Theconnectionof thesheathingtothesupportingmembers

intheseareasismostcriticalandoftenmaybedetailedwithahigherdensityof connectorsthanother

roof areas.

Figure 7-4.

Loss of roof sheathing due to 

inadequate fastening between 

roof sheathing and framing. 

(Source: FEMA 549)
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-5

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

7.3.1 Roof Sheathing

Roof sheathingisthefirststructuralcomponentintheloadpathbetweentheroof systemandthe

foundation.Thefirstenvelopecomponents(i.e.,theroof coveringandroof underlayment)aretypically

non-structuralandarediscussedindetailinChapter8,Roof CoveringandBestPractices.

Theroof sheathingsupportsgravityloads,suchastheroof liveload,snowload,andvertical-upliftloads

createdbywindpressures.Also,theroof sheathing(workinginconjunctionwiththeroof framing)must

functionasadiaphragmtotransferlateralloadstothebuildingsshearwalls.

TheIBC,IRC,WFCM,andICC-600allcontainprescriptiverequirementsforfasteningroof sheathing.

Thefasteningrequirementsarethoserequiredtoresistupliftforcesfromwindpressuresandshearforces

fromlateralloads.

Mostcodesandstandardsallowtheuseof commonnailstoconnectsheathingtosupportingmembers

forsiteswherebasicwindspeedsarelessthan100mph(110mphinnon-hurricane-proneregions)

butrequirering-shanknailsinhigher-windzones.Ring-shanknailshavehigherwithdrawalcapacities

(expressedinratings)andareneededbecausetheyprovideresistancetothehighforcesactingonthe

sheathingpanelsfromtheroof pressuresinhigher-windzones.Anotheroptionistousewoodscrews

inplaceof nailsbecausetheytendtohavehigherwithdrawalcapacities.Bestpracticesrecommendthe

useof woodscrewsparticularlyintheeavesandcornerzonesof theroof,wherewindscancreate

largeuplift(suction)pressures.Unlessdirectedotherwisebydesignprofessionals,woodscrewsshould

have(ataminimum)thesamediameterasthenailsprescribedbythecodesorstandardsandshould

belocatedaccordingtothesamespacinginterval(orbeevenmorecloselyspaced).Itisalsoimportant

tonotethatthedensityof theroof framingmembermustbetakenintoaccountwhendetermining

fastenerspacing.Relativelydenseframing(suchasisachievedwithSouthernYellowPinemembers)holds

fastenersbetterthanlower-densityframing(suchasSprucePineFirmembers)andmayallowforwider

spacingof fasteners.

Thefastenerssecuringroof sheathingmustpenetrateintothesupportingroof framingtoproveeffective.

Shiners(i.e.,nailsthatmissroof framingwhenhammeredintoplaceandwhosemetalsurfacesshine

whenviewedfromtheatticspacebelow)providenostrengthandnowithdrawalcapacityandconstitute

adiscontinuitywithintheloadpath(seeFigures7-5and7-6).Also,fastenersshouldnotbeoverdriven.

Overdrivingthefastenersincreasesthepotentialfortheroof sheathingtoteararoundtheheadsof the

fastenersasthenailheadpenetratesintothewoodsheathing.Theoverdrivingof nailsfrequentlyoccurs

whenpneumaticorgas-powerednailersareusedwithoutpropersettings.Thisissuecanbeaddressed

onsitebyacontractorbyproperlycalibratingthetoolsbeingused.
7-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

Woodstructuralpanelsareratedaccordingtotheirabilitytospanbetweenstructuralmembers.The

prescriptiveportionsof theIBCandIRClisttheminimumthicknessof sheathingdependinguponthe

spacingof theroof framing.Forexample,Table2304.7(1)of theIBCgivesminimumnetthicknesses

of lumberthatmaybeusedinfloorandroof sheathing.TableR803.1of the2006IRCprescribes

minimumnetthicknessesof sheathingdependingonrafter-beamspacingforlumberroof sheathing.

Section307.4of SSTD-10specifiesminimum15/32-inchroof sheathingunlessotherthicknessesare

requiredforadequateroof diaphragmstrength.Table3.12Aof theWFCMspecifiessheathingbased

uponthedesign-windspeedandthespacingof theroof framingfortheExposureBcategoryof wind

exposure.WFCMTableA3.12ArelatestomorestringentExposureCconditions.Higherbasicwind

speedsandwiderroof-framingspacingrequiresthickerroof sheathing.WFCMTable3.12Bspecifies

roof sheathingrequirementsforsnowloads.Inareasexposedtobothsnowandwindloading,themost

stringentrequirementapplies.

Afinalcommentonroof sheathing:Itisimportanttonotethattheunsupportededgesof roof sheathing

canflexexcessivelyunderload.TheAmericanPlywoodAssociationsuggeststhatsupportbeprovided

forpaneledgesexposedtowalkingloads(suchasfloorsandlower-slopedroofs).Theuseof solidblocking

isconsideredbestpracticeasameansof support,butH-clipscanbeusedforadditionaledgesupport.

WhenutilizingH-clips,itisimportanttoconsultthemanufacturersspacingrequirementstoensurethat

adequatestructuralsupportisattainedwiththeclips.

Figures 7-5 and 7-6.

Exterior and interior views of connection issues 

between the roof sheathing and the top chords 

of the roof truss system. (Source: FEMA 55)
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-7

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

7.3.2 Roof Framing

Roof framingisthenextbuildingcomponentfoundwithintheloadpath.Theroof framingmustsupport

theroof deckingandsheathingandresistloadsappliedtothesheathingandtransferloadsverticallyto

supportwalls(orframes).Theroof framingmustalsofunctionaspartof theroof diaphragmtotransfer

lateralloadstotheshearwallsbelow.

Roof framingtypicallyconsistsof dimensionallumberraftersorengineeredroof trusses.Forrafters,

designprofessionalscancalculateraftersizesorsizescanbedeterminedbyprescriptivespantables,such

asthosecontainedintheAF&PAsSpanTableforJoistsandRaftersorTable12of theWFCM.TheIBCand

IRCalsocontainspantables.Raftersmustbesizedtoresistdeadloads(i.e.,theweightof theroof system

includingrafters,sheathing,roofing,andunderlayment,plusanypermanentattachments),roof liveload,

snowload,andwindload.Roof framingmustalsobesizedtocontroldeflections.Inareaswherethe

snowloadislessthan20psf,windloadsoftendictatethesizingof rafters.Inallareas,themoststringent

loadingmustbedeterminedandtherafterssizedappropriately.

Connectionstoresistupliftandadequatelytransferlateralloadscanbedeterminedbyadesignprofessional

orfromprescriptivestandards.Table3.4of theWFCMliststherequiredcapacityof theconnections

betweentheroof framingandwalls(framingorother).Prescriptivedesignsfortoe-nailedconnectionsare

providedinTable3.4A;connectionsusing20-gaugegalvanizedstrapsarelistedinTable3.4B.Tables3.4,

3.4A,and3.4BcoverExposureBconditions.ExposureCconditionsaredetailedinTablesA3.4,A3.4A,

andA3.4B.Anexampleof amasonrywall-to-roof trussupliftconnectionisshowninFigure7-7.

Oversize washer

according to design

(typical)

Connector installed

according to manufacturer’s

specifications

Roof truss anchored

to top plate

Reinforced concrete masonry wall Grout stop

Provide moisture

barrier

Direct roof truss anchor

installed according to

manufacturer’s 

specifications

Roof trusses at 24”on center maximum

Pressure-treated

top plate, as required

(2x4 maximum)

Reinforced

bond beam

Connector (typical)

Roof truss anchored

in bond beam

1

/2”anchor bolt

at 18” to 24”on

center or as specified 

by design

Figure 7-7.

Detail of masonry wall-to-roof trusses. (Source: FEMA 499)
7-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

Fortrussedroofs,thetrussmanufacturertypicallyalsoservesasthetrussdesigner.Therefore,thetruss

manufacturerischargednotonlywithprovidingspecificdetailsrelatingtotrussconstruction(e.g.,thesize

of membersandtrussplates)butalsowithindicatingtheneedforfield-installedtrussbracingthatmay

berequiredtopreventbucklingof compressionmembers.Alltrussbracingmustbeproperlyinstalled

asdirectedintheplans,inorderforthetrussestofunctionasintended.Thetrussdesignergenerally

specifiesbearingandupliftreactions,butdoesnotspecifywhichconnectorsshouldbeusedtosecurethe

trusses.Buildingofficialsandplanreviewersshouldpaycarefulattentiontoensurethatallappropriate

information(suchasthebasicwindspeed)hasbeenprovidedontrussdrawingsbythemanufacturers

andtoidentifywhatadditionalinformationmustbeprovidedbythebuilder.Acopyof thetrussdrawings

shouldberequiredaspartof thepermitsubmittal.Providingconnectorsthatmaybeneededtoresist

upliftandprovideacontinuousloadpathatthislocationwithintheloadpathisnottheresponsibilityof 

trussmanufacturers;theuseof theseconnectorsmustbedeterminedandspecifiedbyothers.Theuse

of connectorsmayberecommendedeitherbydesignprofessionalsorbyprescriptivestandards,suchas

theWFCM.

Informationonroof-frameinspectionpointscanbefoundinFEMA55,Table13.6:Roof InspectionPoints.

Thetableandtheassociateddiscussionprovidesthelocalofficialwithcommonroof constructionitems

thatshouldbenoted,aswellasasummaryof topicsdescribedindetailwithinthissection.

7.4 Wall Construction 

Exteriorwallsarethenextbuildingcomponentfoundwithintheframingsloadpathfromtheroof to

thefoundation.Liketheroof,exteriorwallsmustresistloadsimposedonthem(particularlybywindor

seismicactivity)andtypicallymustfunctionasassembliestoprovidestabilityfortheentirestructure.

Threetypesof loadscanbeimposedonexteriorwalls.First,out-of-planeloads(i.e.,loadsthatexistout

of theplaneof,orperpendicularto,thewall)areimposedonthewalls.Theseloadsresultprimarilyfrom

windbutcanalsoresultfromseismicactivity.Allexteriorwallsareexposedtotheseout-of-planeforces.

Secondly,verticalloads(alsocalledaxialloads)aretransferredintosomewallsfromtheroof (orupperstory

walls)above.Theverticalloadscanbedownward-actinggravityloadsthatresultfromtheweight

of thestructureorupward-acting(uplift)loadsfromwindorseismicevents.Upliftandgravityloadsare

consideredin-planeloadssincetheyoccurwithintheplaneof thewall,butactalongtheverticalaxisof 

thewall.Allload-bearingwallsareexposedtoin-planegravityloads(suchasthedeadloadsof non-loadbearing

walls).Inadditiontothein-planegravityloads,manywallsarealsoexposedtoupliftloads.

Lastly,in-planehorizontalloadscanalsoexistinsomewalls.Theseloadstypicallyresultfromwindforces

imposedonbuildingsurfacesthatareperpendiculartothewalls.Forexample,windloadsactingona

buildingsroof andfrontwallcreatehorizontalloadsinitsleftandrightwalls.Thosehorizontalloads

arecollectedthroughhorizontaldiaphragmssuchasfloorsandroof decks,andarecalledshearloads.

Thewallsthatareneededtoresisttheseloadsarecalledshearwallsorshearpanels.Shearloadsare

in-planeloadssincetheyoccurwithintheplaneof thewall.Shearwallsmayalsobeneededtoresistoutof-plane

loadsfromwindorseismicevents.Inaddition,shearwallsmayfunctionasload-bearingwalls.

Shearwallsthatfunctionasload-bearingwallsareexposedtoallthreetypesof loading(seeFigure7-8).
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-9

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

7.4.1 Wall Sheathing

Asmentionedintheprevioussection,allexteriorwallsmustresistout-of-planeforces.Section602of the

IRCspecifiesminimumwall-sheathingthicknessandfasteningrequirementsforstructuralpanels,plusa

varietyof othersheathingstyles(suchascellulosicfiberboardandgypsumsheathing).Table3.11of the

WFCMspecifiesminimumwall-sheathingthicknessforstructuralsheathingbasedonstudspacingfor

ExposureBconditions.ExposureCconditionsarespecifiedinWFCMTableA3.11.

WhilecellulosicandgypsumsheathingisacceptedbytheIRCaswallsheathing,FEMAandothers

recommendinstallingwoodstructuralpanelsheathingforallexteriorwallsasabestpractice.Itwas

observedduringpost-eventevaluationsthatwoodstructuralpanelsperformbetterandaremoreresistant

towindbornedebristhanothersheathingmaterialsthatareallowedbybuildingcodesfortheprovision

of shearresistance.

7.4.2 Shear Walls

Shearwallsprovidelateralstabilityforastructure.SectionR602.10of theIRCprovidesprescriptive

constructiondetailsandrequirementsforbracedwalllinesandbracedwallpanelsforbuildingsexposed

to3-secondgustbasicwindspeedslessthan110mph(lessthan100mphinhurricane-proneareas).

TheWFCMprovidesprescriptiveshearwalldetailsfor3-secondgustwindspeedsfrom85mphto150

mph.Inaddition,Section305.4of SSTD-10providesshearwalldesignsappropriateforuseinbuildings

exposedtowindspeedsupto110mph(fastestmile). Wind Loading

Strap

King Stud

Jack Stud

Header

Strap

Band Joist

Shear Wall 

Holddown

Connector

Shear Wall Panel

Shear Resistance

Total Wind Uplift Loading contributions

not shown for clarity

Loads transferred down to foundation

Wind Uplift resistance

Transfer of shear loads from 

lateral wind loads

Figure 7-8.

Horizontal loadings exerted on 

exterior walls.

NOTE

Although exterior walls are 

typically framed with 2 by 4 

lumber, the use of 2 by 6 lumber 

should be considered. Using 

2 by 6 lumber increases the 

strength of the exterior walls 

and offers a larger cavity for 

insulation, thus increasing the 

energy efficiency of the building.
7-10 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

Shearwallsmayalsobeconstructedwithmasonry,concrete,ICF(InsulatedConcreteForms)andwith

structuralinsulatedpanels(typicallyreferredtoasSIP).SIPsconsistof woodstructuralpanelswhich

sandwicharigidinsulationcore,whichistypicallypolystyrene(althoughurethaneisalsoused).

Whenanalyzingshearwalls,twoclassificationsof shearwallsexist.Segmentedshearwallsarefull-height,

fullysheathedwallsegmentsthatfunctionindependentlytoresistlateralloads(seeFigure7-9).

Figure 7-10.

Perforated shear walls.

FIGURE 7-9

FIGURE 7-8

= Shearwall

= Compression Force

= Tension Force

= Shear Force

SEGMENTED SHEARWALLS

PERFORATED SHEARWALLS

= Shearwall

= Compression Force

= Tension Force

= Shear Force

HOLDDOWN

CONNECTOR

HOLDDOWN

CONNECTOR

= Portion of wall not designed to provide resistance to shear loads

WIND OR SEISMIC

LOAD

WIND OR SEISMIC

LOAD

NOTE

Special care should be used 

when utilizing or checking a 

design based upon the WFCM 

tables (or any prescriptive tables) 

to ensure that all apporpriate 

adjustment factors are bing 

correctly applied. 

Perforatedshearwallscontainframedopeningsforwindowsanddoors.Perforatedshearwallsrelyupon

continuousstructuralelementsoverwindowsanddooropeningstomaketheshearwallfunctionasa

singleunit(seeFigure7-10).Theseelementsarecalleddragstruts.

Forwinddesign,theWFCMliststhetotallengthsof segmentedshearwallsrequiredinahomein

ExposureBareasforwindsperpendiculartotheroof ridge(Table3-17A)andparalleltotheroof ridge

(Table3-17B).ExposureCrequirementsarelistedinTablesA3-17AandA3-17B.Seismicrequirements

arelistedinTable3-17C.

FIGURE 7-9

FIGURE 7-8

= Shearwall

= Compression Force

= Tension Force

= Shear Force

SEGMENTED SHEARWALLS

PERFORATED SHEARWALLS

= Shearwall

= Compression Force

= Tension Force

= Shear Force

HOLDDOWN

CONNECTOR

HOLDDOWN

CONNECTOR

= Portion of wall not designed to provide resistance to shear loads

WIND OR SEISMIC

LOAD

WIND OR SEISMIC

LOAD

Figure 7-9.

Segmented shear walls. 
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-11

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

PerWFCMSection3.4.4.2,theshearwalllengthstabulatedarebaseduponastandardshearwall.The

standardwallisablocked1

shearwallconstructedwith7/16-inchwoodenstructuralpanelsattachedwith

8dnails6inchesoncenters(atpaneledges)and12inchesoncenters(withintheinteriorof thepanel,

alsocalledthefield).Theinsidesurfaceof thestandardwallorshearwallpanel(i.e.,thesurfacethatis

exposedtothefinished/livingspace)issurfacedwith-inchgypsumdrywallsecuredwith5dcoolernails

at7inchesoncentersalongedgesand10inchesoncenterswithinthepanel.Thesestandardshearwalls

provideashearcapacityof 436poundsperlinearfoot.Adjustmentfactorsforvariationsonstandard

shearwallconstructionareprovidedinTable3.17D.Shearwallswithlowershearcapacityrequirelonger

walllengths;wallswithhighershearcapacityrequireshorterwalllengths.

TheWFCMcontainscriterianeededforconstructingperforatedshearwalls.Thecriteriaaredetermined

bymultiplyingthetabulatedshearwalllengths(infeet)listedforsegmentedshearwallsinTable3.17A,

3.17B,or3.17CbyadjustmentfactorslistedinTable3-17Eforperforatedshearwalls.Theadjustment

factorsinTable3.17Earebaseduponthesizeandaspectratios(height/widthratios)of theframed

openingswithintheperforatedshearwalls.Tables3.17Aand3.17Blisttheminimumsegmentedshear

walllengthsrequiredtoresistwindloads.(Table3.17AisforshearwallsparalleltothewindandTable

3.17Bisforshearwallsperpendiculartothewind.)WhileTables3.17Aand3.17Baddressshearwall

requirementstoresistdesignwindevents,Table3.17Clistsshearwallrequirementsforseismicevents.

LikeTables3.17Aand3.17B,Table3.17Cprovidestherequiredlengthof segmentedshearwalls(in

feet).UnlikeTables3.17Aand3.17B(whichlisttheminimumlengthsof shearwallsegments),Table

3.17Ccontainsformulasnecessarytodeterminethoselengths.

Forexample,if Table3.17Arequiresaminimumof 15feetof shearwallsegmentsbeprovidedtoresist

windsperpendiculartotheridgeandTable3.17Elistsaperforatedshearwalladjustmentfactorof 

1.33baseduponthesizeandaspectratiosof openingswithinthatwall,then20feet(15feetx1.33)of 

perforatedshearwallmustbeprovided.

Generally,greaterlengthsof perforatedshearwallsareneededtoresistlateralloadsthansegmented

shearwalls.Also,inperforatedshearwalls,moreattentioninthedetailinganddesignisneededabove

doorsandwindows,whereframingfunctionsasdragstruts.Thegreaterattentionisneededtoensurethat

thedragstrutsandtheirconnectionsareadequatetotransferin-planeloadsthroughtheshearwall.The

benefitof perforatedshearwallsisthattheyonlyneedtobeanchoredattheirendswhiletheendsof each

segmentof asegmentedshearwallneedtobeanchored.Thisisdiscussedinthefollowingsection.

7.4.2.1 Shear Wall Anchorage

Shearwalls(whethersegmentedorperforated)mustbeanchoredtothefoundation2(ortheshearwall

belowwhenonanelevatedfloor)tocompletethecontinuousloadpathwithinthisareaof thebuilding.

Aproperanchorageorconnectionpreventstheshearwallsand,inturn,therestof thestructurefrom

laterallyracking,displacing,oroverturningduringahigh-windorseismicevent.

2

 Small, relatively heavy homes (or homes placed in low-wind areas) may have sufficient weight to avoid requiring

 shear-wall anchorage. Even in such instances, shear-wall anchorage is advised for structural redundancy.

1

 Blocking is short framing members installed between wall studs or floor joists. Blocking provides a method to 

fasten the unsupported edges of sheathing panels.
7-12 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

Segmentedshearwallsneedtobeanchoredattheedgesorendsof eachshearwallpanel.Perforated

shearwallstypicallyonlyneedanchorageattheirends.Figure7-11illustratesatypicallargeanchorthat

maybeconnectedattheendpostof aframedshearwall.

Figure 7-11.

Shear wall anchor. (Source: FEMA 55)

Shearwall Holddown

Connector Bolted 

Through Stud

Wall Stud

Wall Stud

Band Joist

Bottom Plate

Pile

Two-Member

Floor Support

 Beam

Shearwallanchoragecapacitiesformulti-levelbuildingsareadditive.Inotherwords,anchoragefor

upper-levelshearwallsneedstobeprovidedinadditiontofirst-flooranchorage.Wheresegmentedshear

wallpanelslineupvertically,thepanelscanshareanchoragedevicesprovidedtheanchoragedevice

iscapableof resistingthetotalloadforallshearpanelsthatitanchors.Thesameistruefortheendsof 

perforatedshearwalls.Multi-levelperforatedshearwallscanshareanchorageattheirends,providedthe

anchoriscapableof resistingshearwallreactionsforalllevels.

Thereactions(loads)attheendsof shearwallsareproportionaltowallheight.Tallerwallsdevelop

largerreactionsandrequirestrongeranchors,andanchoragerequirementsforevensmallhomescan

bethousandsof pounds.Table3.17Fof theWFCMlistshold-downrequirements(inpounds)forwall

heightsrangingfrom8feetto20feet.Manyanchortypesandstylesareavailableandshouldbedesigned

basedonthemanufacturerspublishedanchorcapacities.Anexampleof ananchorisshowninFigure

7-11.Forload-pathcontinuity,anchorsshouldextendfromshearwalltoshearwall(if thebuildinghas

severallevels)andeventuallyintothefoundation.Shearwalltie-downsgenerallyresistortransfervertical

loadsonly;otherfastenersareneededtoresistthehorizontalloads(calledbaseshear)thataccompanywind

orseismicevents.

7.4.2.2 Gable End Walls

Gableendwallfailurescontinuetobeobservedafterhurricanesimpactstructures.Thegableendwalls

arethosethatareorientedparalleltoroof/floorframingandextendpastthetopplateof thewallframing

anduptotheroof ridge.Gableendwallsdonotsupporttheroof anddonotbenefitfromthelateral

supportthattheroof framingprovidesunlesstheyarejoinedbystructuralmembersorconnectors.
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-13

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

Gableendwallconstructionrequirementsarereasonablywell-detailedformasonryandconcretebutless

guidanceisprovidedforwoodframing.Figure205E4of ICC600containsadetailof gableendbracing

foramasonrywallwithawood-framedgable(seeFigure7-13),butICC600doesnotprovidedetailson

bracingawood-framedgableatopawood-framed(ormetalstud)wall.

Figure305Jof SSTD-10indicatesthatgablesshouldbeballoon-framed(withverticallycontinuousstuds

acrosstheceilingdiaphragm(seeFigure7-12)andFigure305Kof SSTD-10showsplatform-constructed

gablewalls(i.e.,thoseconstructedwithatopplate)butonlyshowswallsbeingsecuredtothefinish

sheathingof theceilingdiaphragm,andnotastructuralmemberfromtheroof-framingsystem.SSTD10

Section306.3specifiestheuseof bracingceilingjoists/trussbottomchordswith6-foot-longlateral

bracesatmaximum6-footintervals,butthebracingisnotshowninthegraphicdetails.

Figure 7-12.

Example of balloon framing. Blocking

Full-Length Studs

NOTE

Gable end walls may be 

constructed through a variety of 

different building materials and 

techniques, but the discussion 

presented here is primarily 

focused on framed construction.

NOTE

Balloon framing is a construction 

technique reserved for specific 

applications and cannot be 

used in certain applications, due 

to restrictions on the height of 

members. It is typically possible 

for one-story houses, but 

balloon framing does not usually 

work for two-story houses.

Truss

Bottom

Chord Lateral

Bracing

Compression

Blocking

Double

Top Plate

Gable

End Truss

Bottom

Chord

Additional

Stud

Gable

End Stud

Compression

Blocking

Lateral

Bracing

Truss

Figure 7-13.

Additional bracing at a gable end wall. 
7-14 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

Asabest-practicesapproach,theceilingdiaphragmshouldbeconstructedwithwoodframingand

thegableendwallshouldbebracedtothatframing.IBHS(InstituteforBusinessandHomeSafety),

FEMA,andotherentitieshavedevelopedmethodstobracewood-framedgablestowood-framedwalls.

Figure7-13providesanexampleof agableendwallbracingscenario.(TheHurricaneRetrofitGuide,

availableathttp://www.floridadisaster.org,providesseveralexamplesof variousframingsituations.)

Tallergablesmaylackadequateframingtoresistwindloadsandpressures;bracingthemid-pointof longer

studsusedintallgableendwallsmaybenecessaryinordertomeetdesignloads.Designprofessionalscan

designanddetailthebracingfortallergablewalls.

Gablewallsonbuildingswithcathedralceilingsoftenhaveanaddeddisadvantage.Withcathedralceilings,

thetopplateof thebuildingsgablewallmaybeoffsetfromtheslopedceilingdiaphragm(seeFigure14).

Whenoffset,theceilingdiaphragmcannotprovidelateralsupportfortheportionof thewallwhere

thetopplateislocatedanareathatisinherentlyweakandvulnerabletoout-of-planeforcesactingon

thewall.

Figure 7-14.

Improperly braced gable walls. 

The ceiling diaphragm (i.e., the 

bottom chords of the scissor truss) 

is located several feet above 

the top of the end wall top plate 

and no wall-to-truss bracing is 

provided. (Source: FEMA 549)

Toaddressgableendwallweaknessesthatmayexist,properbracingisneeded.Forconventionalframing,

augmentingthecode-referencedbracingmethodswithcross-bracingsecuredtotheraftersandceiling

joists(ortothetopandbottomchordsof roof trusses)issuggested(seeFigure7-13).Forbuildingsframed

withcathedralceilings,twoactionsarerecommended.First,thegableendsshouldbeballoon-framedand

constructedsowallstudscontinueunsplicedacrosstheceilingdiaphragm.Secondly,theupperportionof 

theframingshouldbebracedasdetailedforconventionalgableends.

7.4.2.3 Interior Shear Walls and Moment Frames

Occasionally,buildingsarelaidoutinsuchamannerthatinsufficientspacehasbeenallocatedforthe

constructingof adequatestandardexteriorshearwallstoresistlateralloads.Thiscanoccurwith

relativelylongandnarrowbuildingsorwhen(asinthecaseof manycoastalhomes)designersand
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-15

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

homeownerswanttomaximizetheamountof windowsinstalledinahome.Insuchcases,afewoptions

existforprovidinglateralload-resistingsystems.

Afirstoptiontoaddressthelackof exteriorshearwallsinvolvesmakingtheexteriorshearwallsstronger

inordertoresistgreatershearforces.Installingstructuralpanelsonbothsidesof thewallframingcan

increase(andwilltypicallydouble)theloadcapacityinashearwall.Keepinmindthatwithlargershear

forces,shearforcesattie-downsbecomegreaterandadequatetie-downandanchoragebecomemore

difficulttoachieve.

Asecondoptionistoconstructinteriorshearwalls.Interiorshearwallsaretypicallydesignedtobe

stronger(i.e.,havemoreloadcapacity)thanexteriorshearwallsbecauseinteriorshearwallsresistshears

collectedfromdiaphragmslocatedonbothsidesof theinteriorshearwall(whileexteriorshearwalls

onlycollectloadsfromdiaphragmsononeside).Interiorshearwallstypicallyneedtobelocatedover

foundationwallsoroveralineof pilingsorpiers.Thisisrequiredtoensurethatthereactionsdeveloped

intheshearwallscanbeadequatelytransferredtothefoundation.

Athirdoptionistoconstructinteriormomentframes.Further,momentresistantframesareconsidered

specializedconstructionandarenotaddressedinprescriptivecodesorstandards.Toensureadequacy,

therefore,momentresistantframesshouldbedesignedbyastructuralengineer.Oncedesignedbythe

engineerfortheappropriatewindandfloodloads,thefabricationof steelmomentresistantframeswill

usuallybeperformedbyasubcontractorthatspecializesinsteelfabricationanderectionandwhoshould

firstprepareasetof shopdrawingsfromthedesigndrawingsforreviewbythebuildingdepartment.

Thecontractoranddesignershouldbothchecktheaccuracyof thesubcontractorsshopdrawings.Most

momentresistantframeswillhavetobetransportedinsectionsandassembledonsitethroughfieldbolting

orwelding(seeFigure7-15).

Figure 7-15.

Residential use of a moment 

resistant frame. (Source: FEMA 55)

DEFINITION

Moment Resistant Frame – A 

series of columns and beams 

which resists lateral loading 

through its ability to bend. 

Typically utilized in residential 

construction, moment resistant 

frames are often used in 

combination with shear 

wall systems.
7-16 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

7.4.3 Headers, Beams, and Girders

Headersarehorizontalbeamsconstructedtosupportloadsoverframedopenings.Headersaretypically

requiredoverallopeningsinexteriorwallsandoverallinteriorload-bearingwalls.Headerssupportnot

onlygravityloads(e.g.,liveloads,snowloads,anddeadloads)butmustalsoresistupliftloadsfromwind

events(seeFigure7-16).

Tables3.22Athrough3.22Eof theWFCMcontainheadersizesforgravityloadsforvariousbuilding

types(single-,two-,andthree-story),variousbuildingwidths(from12to36feet),andrangesof ground

snowloads(from30to70psf).Table3.23Aprovidesheadersizesforopeningsinwallsexposedtowind

loadsfor3-secondgustwindspeedsupto150mph.Inareaswherethe3-secondgustbasicwindspeedis

110mphorless,gravityloadstypicallycontrolheadersize.Inareaswherethe3-secondgustbasicwind

speedexceeds110mph,windloadsmaycontrol.Bothtablesneedtobecheckedandthemostrestrictive

of themshouldbeusedtodetermineheadersize.Table3.23ArelatestoExposureBconditions;Exposure

CconditionsarelistedinTableA3.23AinAppendixAof theWFCM.

Eachendof headersshouldhaveupliftconnectorstoresistwindupliftforcesandtocompletetheload

path.ThewindforcesthatconnectorsmustresistinExposureBareasaretabulatedinWFCMTable

3.7;upliftforcesforExposureCareasaretabulatedinWFCMTableA3.7.Theupliftconnectionsare

baseduponaroof deadweightof 15psf (andothercriteriathatmustbemetforthesetabularvalues

toremainvalidforaparticularapplication).Itshouldbenotedthatthesevaluesareconservativefor

heavierroof structures.Forbuildingswithlighterroof structures,upliftloadsneedtobedeterminedbya

designprofessional.

Figure 7-16.

Uplift connections for headers. (Source: FEMA 499)

LINK

The bottom of a wall could 

have points of high uplift due 

to an accumulated load from 

above. Suitable hardware

shoud be installed in the

proper locations.

LINK

An adequate connection must 

be made between the header 

and the king stud in order for 

the load to continue around the

opening down the path.

Uplift From Roof

Header

Rim joist

King stud

Jack stud

Strap

Strap
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-17

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

Thebottomsof framedopeningsforwindowsalsoneedtobeproperlyconnectedtoresistout-of-plane

loads.Window-sillplatesaresizedinTables3.23B(ExposureB)andA2.23B(ExposureC);andlateral

forcesactingonwindowsillsmustalsoberesisted.TheseloadsaretabulatedinTables3.8andA3.8for

ExposureBandCareas,respectively.

Girdersarehorizontalmemberswhichcollectloadsandsupportfloorframingandfloorjoists.Girders

connectthefloorsystemstothecolumnsorpostsof thefoundation.Unlikeheaders(whichareconstructed

integrallywithwallsthatcanresistshear),thegirdersandpostsusedinwood-framedconstructionare

typicallynotpartsof thelateralload-resistingsystemandareusedtosupportgravityloadsonly.

TableR502.5(1)of theIRCprovidesprescriptivedesignsforgirdersbaseduponthedistancebetween

supports,numberof floorssupported,andwidthof thehome.Thetablelistsrequirementsfordimensional

lumberandspecifiestheuseof built-upbeamswithathicknessof uptofourplies.Thetableisbased

uponsimplysupportedbeamswhereindividualmembersof thebeamaresplicedoverthesupports.In

theIBC,Tables2308.9.5and2308.9.6providewood-headerandgirder-spanrequirementsforexterior

andinteriorload-bearingwalls,respectively.Thespansareafunctionof thebuildingconstructiontype

(one-ortwo-storydwellings),headerorgirdersize,andbuildingwidth.

Designingbuilt-upbeams(wheresomeof themembersareusedinacontinuousmanneroverthe

supports)will:1)resultinmoreefficientdesignsthatrequirelessframingmaterial,and2)typicallyresultin

significantreductionsindeflection.Whereveraspliceismade,thesplicedmemberdoesnotcontributeto

beamstrength,socorrectlylocatingsplicesiscriticalforensuringproperperformance.Splicesneedtobe

placedinlocationswhereinducedmomentsinthebeamarelow.Engineersshoulddesignbeamsthatare

consideredtobecontinuousoversupportsandshoulddetailwheresplicesintheindividualmembers

arelocated.Continuousbeamscarrymomentforcesinthebeamsacrossthetopof thesupportingpost

orcolumn.Bycontrast,simplysupportedbeamshavezeromomentatthesupportingpostorcolumn.

7.4.4 Concrete, Masonry, and ICF Walls 

Theuseof wallsconstructedfromreinforcedconcreteorconcrete

masonryunits(CMU)isbecomingmoreprevalentincommunities

impactedbyhurricanes.Whenproperlydesignedandconstructed,

thesestylesof wallscanperformwellwhenexposedtohighwinds.

Typically,concreteandCMUconstructionisusedinconjunction

withwood-framedroofsand,inthecaseof multi-storybuildings,

wood-framedfloors.Concreteandmasonrywallslackthethermal

performancerequiredbytheIRCandtypicallyrequireframedwalls

orthickfurringtoallowtheadditionof sufficientinsulation.Butwith

theadventof ICF(InsulatedConcreteForm)wallsections,sufficientthermalandstructuralperformance

canbeobtainedwithasingle,reinforcedconcrete-wallsectionbecauseitspermanentinsulatingform

remainsinplace.Figure7-17illustratesawell-designedmasonrywallsystem.

NOTE

Insulating Concrete Forms 

(ICF) are used in a construction 

technique that utilizes preformed blocks or panels to form 

a pre-insulated wall system 

that relies upon concrete for 

its structural integrity. More 

information about acceptable 

ICF applications is available in 

the IRC. 
7-18 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

RequirementsformasonryshearwallsarespecifiedinSectionsR606,R607,andR608of theIRC.The

IRCcontainssomeprescriptivedesignsformasonrywalls(e.g.,wallreinforcement,minimumwidthof 

walls,rafterandjoistconnections,andfloordiaphragmconnections),however,therewillbesomeaspects

of masonryconstructionthatwillneedtobedesigned.Forexample,IRCSectionR606.12.2.2.1requires

thatconnectionstoshearwallsbedesignedinaccordancewiththeperformancestandardACI530/

ASCE5/TMS402,BuildingCodeRequirementsforMasonryStructures.RequirementsforICFconstructionare

providedinIRCSectionR611.TheprescriptivedesignsforICFarewell-developedanddetailed.

Examplesof prescriptivedesignsforconcreteandmasonrywallsinhigh-windregionsarecontainedin

Section205.5of ICC600.Itisimportanttonotethatreinforcementisspecifiedforwallsbothparallel

toandperpendiculartotheroof ridgeforone-,two-,andthree-storybuildings.PrescriptiveICFdesigns

thatmeethigh-windrequirementsof theIRCmaybefoundinSection209of ICC600.

Informationonwall-framinginspectionpointscanbefoundinFEMA55Table13.5:WallInspection

Points.Thistableprovidestheofficialwithcommonitemsthatshouldbeinspectedorobservedinwallframing

construction,aswellasasummaryof thetopicsdescribedwithinthissection.

7.5 Floor Construction

Peoplearegenerallyquiteawareof thefloorsonwhichtheyliveandwork.Peoplenoticethesqueakof 

aloosefloorboard,feelthesoftnessof plushcarpet,andexperiencethefatiguethatresultsfromstanding

onhardconcreteslabs.Manypeopleareunnervedwhenfloorsgiveordeflecttoomuchunderfoot

Anchor roof structure and 

framing to bond beam

Secure decking to

rafter with additional 

nails or screws

Vertical reinforcing is typically doweled

into or connected with L-shaped bars

into the bond beam and footing;

splices shall be lapped in

accordance with code

Brace gable ends

#5 vertical bar in grouted cell,

as required by wind design;

typically at all openings and 

4 feet to 8 feet on center

Horizontal “dur-o-wall” steel reinforcing between block 

cources; vertical spacing determined by engineering analysis

Reinforced concrete bond beam:

Bond beam will typically have a width on not less than a nominal 

8 inches, have a height of not less than 12 inches, and be reinforced 

with #5 reinforcing bars besigned to resist wind loads at the site

Bond beam shall be connected to each truss or rafter member with

hurricane straps or anchors

Figure 7-17.

Design of a reinforced 

masonry wall system. 

(Source: FEMA 488)
FEDERAL EMERGENCY MANAGEMENT AGENCY 7-19

BUILDING FRAMING SYSTEMS AND BEST PRACTICES 7

traffic.Whatmanypeoplearenotawareof isthestructuralimportanceof floorsystems.Inadditionto

supportingabuildingsoccupants,floorsystemsarecriticalcomponentsinresistinglateralloads.

Floors(andceilings)functionasdiaphragmsandcollectlateralloadsthathavebeenexertedonabuildings

exteriorfromwindorfloodforces.Floorsystemstransferloadseithertoshearwallsinthestoriesbelow

or,inthecaseof thelowestfloor,tothefoundation.Floorsandceilingspreventtorsionalrackingof the

buildingandtogetherconstituteamajorcomponentof thatbuildingsstructure.

Olderversionsof prescriptivecodesandstandardsconcentratedonfloorconstructionthatresistedgravity

loads.Emphasiswasplacedonthepropersizingof floorjoistsforadequatestrengthanddeflectioncontrol

(becausedeflectionof thefloorisoftenthegoverningcriteriawhenselectingmembersizes,spacing,and

themaximumspanof floorjoists).Newercodesandstandards(i.e.,thoseissuedafter1990)placean

increasingemphasisonlateralloads.Detailsareprovided(intheformof prescriptiveorperformance

requirements)toensurethatfloorsystemsfunctionasdiaphragmsandadequatelytransferloadsthrough

thestructure.

Itisrecommendedthatbuildingsbeconstructedhigher,theNFIPrequiresstructuresbuiltinAZonesbe

elevatedtoatleasttheBFEandthatallmaterialsbelowtheBFEbeflood-resistant.Infloodproneareas,

elevatedwoodframedfloors,floorjoists,floordeckingandinsulationallneedtobefloodresistantif they

arenotelevatedabovetheBFE.Thiscriteriatypicallyrequirestheframingandflooringtobetreatedto

resistmoistureanddecayandprecludestheuseof fiberglassbattinsulation.

7.5.1 Floor Framing and Sheathing

Likeroof framing,floorframingtypicallyconsistsof dimensionallumberspanninganopenarea;these

membersarecalledfloorjoists.Theuseof engineeredwoodproductssuchasfloortrussesandIjoists

(seeFigure7-18)isbecomingmorecommoninfloorframing,especiallywhenlong,openareas

aredesiredbeneaththeelevatedfloor.Fordimensionallumber,designprofessionalscandeterminejoist

sizesortheycanbedeterminedusingspantables,suchasthosecontainedintheAF&PAsSpanTablefor

JoistsandRaftersortheWFCM.TheIBCalsocontainsspantablesforavarietyof lumberspeciesand

loadingconditions.

Asmentioned,theuseof floortrussesandI-joistsisbecomingmoreprevalentinfloor-framingsystemsin

manypartsof theUnitedStates.Theproperinstallationof thesematerialsmayrequireadditionalsteps.

Forexample,someI-joistsrequiresolidblockingtopreventwebcrushingunderbearingwalls(suchas

whereawallaboveisbeingsupportedbyafloorwithouttheuseof abeamorgirder).Wherelonger-span

floorframingisinstalled,blockingisneededforlateralsupport,asistypicalinlonger-spandimensional

lumberfloor-framingapplications.Whenusinganyengineeredproduct,themanufacturersinstallation

proceduresmustbefollowedtoensurethatthesystemfunctionsasdesigned.

Floorjoistsmustalsobesizedtoresistdeadloads(i.e.,theweightof thefloorsystemincludingjoists,

floorsheathing,andflooring,plusanypermanentattachments)andliveloads.Inaddition,maximum

allowabledeflectionscorrespondingtobeamlengtharespecifiedinthecodeandmaterialstandards.Itis

importanttonotethat,inmostcases,floor-framingdeflectionlimitsaremorestringentthanroof-framing

deflectionlimits.
7-20 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

7 BUILDING FRAMING SYSTEMS AND BEST PRACTICES

Perimeterframingof thefloorsystemmustpreventthefloorsystemfromrackingandfunctionasa

collectortotransferforcestotheshearwallsorfoundationbelow.TheIRC,ICC-600,andtheWFCM

allcontainprescriptiverequirementsforblockingandforconnectionstowallsplates(locatedabove)and

sillplates(below).

Gravityandliveloadstypicallycontrolthedesignorspecificationof thethicknessof floorsheathing.In

addition,floorsheathingmustbeconstructedinafashiontocreatediaphragmsthatresistlateralloads.

Section503of theIRCspecifiesboardsandstructuralpanelstobeusedasfloorsheathingforvarious

joistspacingandfloorliveloads.

Theprovisionsof prescriptivecodesandstandardsgenerallyaddressmostfloorconstructionsituations.

Theycovermanyissuesthattypicallyariseinacoastalenvironment.Onearea,however,wherethe

provisionof additionaldetailsiswarrantedconcernstheprotectionof metalfastenersagainstsaltspray.

Whilemuchdiscussiononcorrosionprotectionhasgoneintocodedevelopment,thecorrosionof metal

buildingelementsunderelevatedstructuresremainsapotentiallyseriousproblem.Fastenersunder

elevatedstructuresareexposedtosaltspraybutarenotexposedtothecleansingactionof rain.Also,the

undersidesof elevatedstructuresarenotexposedtosunlightandcanremaindamplongerbecauseof 

theirshelteredlocation.Theuseof hot-dippedgalvanizedfastenersprovidesconnectorswithareduced

rateof corrosion(whencomparedtountreatedconnectors).Butsinceportionsof thegalvanizedareas

areoftendamagedwhennailsaredriven,evengalvanizingisnotconsideredfullyeffectiveinresisting

corrosion.Stainless-steelconnectorsprovidethemostcorrosionresistanceofferedinametalconnector,

buttheavailabilityof stainless-steelfastenersandframingconnectorsislimitedinsomeareas.

Onemethodtoreduceexposuretosaltsprayistosheaththeundersidesof floor-framingsystemsin

ordertoenclosethespacewhereconnectorsarelocated.Plywoodsheathing(atleast-inchthick)is

recommendedandshouldbeinstalledtoenclosethefloor-framingsystem.Sheathingshouldbescribed

aroundutilityandframingpenetrationstoreducetheinfiltrationof salt-ladenair.Methodsthatallow

portionsof thesheathingtoberemovedtoallowperiodicinspectionshouldalsobeconsideredand

incorporatedintoanydesign.Further,sincemetal-platewoodtrussesmaybecomeunstableunder

gravityloadswhentheirmetalplateslosestrength,metal-platewoodtrussesshouldnotbeusedincoastal

environmentsunlesscorrosionisadequatelycontrolled.

Informationonfloor-framinginspectionpointscanbefoundinFEMA55,Table13.4:FloorFraming

InspectionPoints,whichprovidestheofficialwithcommonitemsinfloor-framingconstructionthatshould

benoted,aswellasasummaryof topicsdescribedindetailwithinthissection.

Figure 7-18.

Wooden I-joists used for floor 

framing. (Source: FEMA 55)
FEDERAL EMERGENCY MANAGEMENT AGENCY 8-1

ROOF COVERINGS AND BEST PRACTICES 8

Roof Coverings 

and Best Practices

8.1 Introduction 

During

stormevents,aroof isexpectedtoperformmanyfunctionsfrompreventingwaterintrusion

toactingasastructuraldiaphragmincertainsituations.Asstatedinthe2006IBC,roofsmust

servetoprotectthebuilding.Thisrequiresroofstoresisthighandlowtemperatures,rain,winddriven

rain,highwinds,exposuretoultravioletradiation,and(insomeareas)snow,iceformation,andhail

stones.Incoastalareas,highwindsandthehazardsthatoftenaccompanyhighwinds(suchaswindborne

debrisandwind-drivenrain)canproveparticularlyproblematic,asthisisnotspecificallyaddressedbythe

codes(despiteafewexceptions).Corrosionfromsalt-ladenaircanalsobeafactorintheperformanceof 

roof coveringsasmaterials,systems,orfastenerscanbeweakenedfromextensivecorrosion.Roof systems

typicallyfailwhenwindsproduceforcesgreaterthantheroof sstrength.Windscantearroof coverings

fromroof decksandcantearroof decksfromframing.Roofscanalsofailif puncturedbywind-borne

debris.Inmostcases,debrispuncturesarelessof aproblemonresidentialstructuresweretheroof sslope

limitstheamountof rainthatcanenterapuncture(unlessthepunctureoccursinavalleyorotherareas

of theroof wherewaterischanneledorcollected).However,inbuildingswithflatorlowslopedroofs,

puncturesfromwind-bornedebriscanbedevastating.

Roof systems(rangingfromroof coveringstostructuralmembers)typicallyfailwhenwindsproduceforces

greaterthanthecapacityprovidedbytheelementsof theroof system.Windscantearroof coverings

fromroof decksandcanseparateroof decksfromframing.Roofscanalsofailif puncturedbywindborne

debris.Inmostcases,debrispuncturesposelessof aproblemonresidentialstructures,wherearoof s

slopemaylimittheamountof rainthatcanenterapuncture(unlessthatpunctureoccursinavalley

orotherareaof theroof wherewaterischanneledorcollected).However,inbuildingswithflatorlow

slopedroofs,puncturesfromwindbornedebriscanleadtoextensiveinteriordamage.

Historically,damagetoroof coveringsistheleadingcauseof buildingproblemsduringhurricanesand

othercoastalstormevents.Highwindsandwindbornedebriscandamagetheroof coveringandrains

thataccompanythosehighwindscanenterthebuilding,soakingitscontentsandinterior(Figures8-1and

8-2).Afterwaterentersabuilding,excessmoisturebecomestrappedwithinthebuildingandmoldcan

growuncheckedunlessactionsaretakenquicklytosecureanddrythebuilding.Roof problemscanoccur

inanyarea;incoastalenvironmentsthathavehigherwindspeedsandgreaterpotentialfortorrential

rains,problemsresultingfromroof systemdamageandfailuresaremoreprevalent.
8-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

8 ROOF COVERINGS AND BEST PRACTICES

Roof systemscanalsofailif roof-mountedequipmentisdamagedordislodgedbyhighwinds.During

HurricaneKatrina,lossof mechanicalequipmentcausedthemajorityof waterdamagethatwasobserved

inseveralbuildings.Insomeof thosebuildings,structuralroof damageitself wasquiteminimalyetthe

buildingsexperiencedextensivewaterdamage.

Figure 8-1.

Instance where wind pressures 

exceeded the strength of the asphalt 

roofing. (Source: FEMA 549)

Figure 8-2.

GULFPORT, MISSISSIPPI:

Winds dislodged roof mounted 

equipment and created large 

openings in the roof system.

(Source: FEMA 549)
FEDERAL EMERGENCY MANAGEMENT AGENCY 8-3

ROOF COVERINGS AND BEST PRACTICES 8

Therearemanyparameterstoconsiderwhengoodroof performanceisdesired.Althoughthisprocess

beginswiththeproperselectionof theroof systemforthatparticularenvironment,thereareotherimportant

factorstoconsider,suchastheroof covering,deck,ends,underlayment,flashing,andothercomponents.

Properroof installationisachievedthroughexperienceandsoundconstructiontechniques,thorough

inspections,andcompliancewithcoderequirements,standards,andmanufacturerrecommendations.

Otherstepscanbetakentoproduceroofsthatcanperformbetterthancode-mandatedsystems.Those

steps,oftencalledbestpractices,willbediscussedinthefollowingsections.

8.2 Roof Coverings – General Code Requirements

Buildingcodesproviderequirementsforthedesignandinstallation

of roof coverings.Roof coveringsareaddressedinChapter15of the

IBCandChapter9of theIRC.Bothcodesproviderequirements

forroof coveringscommonlyusedonhigh-slopedroofs(suchas

asphaltshingles,clayandconcretetile,woodshakesandshingles,

andmetalroofing)andforroof coveringstypicallyusedforlow-slope

applications(suchasbuilt-uproofing,thermosetsingle-plyroofing,

thermoplasticsingle-plyroofing,sprayedpolyurethanefoamroofing,

andliquid-appliedcoatings).Bothcodesalsocontainrequirements

forroof decks,underlayment,flashing,structuralperformance,

andmaterialsandtestingcriteria.Requirementsforroof coverings

installedinhigh-windareas(i.e.,wherethebasicwindspeedis110mphorgreater)areprovided.Further,

bothcodescontainprovisionsforre-roofingexistingbuildings,whichwillbediscussedlaterinthischapter.

Chapter5of SSTD10containsrequirementsfortheinstallationof asphaltshinglesandconcreteroof 

tilesinhigh-windareas.Itisimportanttonotethattherequirementsapplyonlytoshingleandtile

fasteninganddonotaddressunderlayment,flashing,andotherroof-coveringcomponents.Teststandards

suchasASTMD7158areavailabletoprovideperformancemetricsforasphaltshingles.ThenewICC600

standardistheresidentialdesignstandardforhurricane-resistantconstruction,replacingSSTD10,

andtoreferencetheASTMD7158standard.

WhiletheIRCisgenerallyconsideredaprescriptivecode,manyof theroof-coveringprovisionsare

performance-basedandmimicthosecontainedintheIBC.Theperformanceof moreresearchhasbeen

recommendedinrecentFEMAMATreportsinordertounderstandandidentifyacceptablesystemsand

appropriate(i.e.,compliant)installationtechniquesforresidentialapplications.

Thetechnicalnatureof theseroofingsystems,andhowtheyrelyuponinstallationforcode-compliance

andwarrantycompliance,isoftenmuchmoreinvolvedthanotheraspectsof residentialconstruction

(suchaswallandroof framingorfoundationconstruction).Thecodesoftenrelyupontheuseof the

manufacturersinstallationinstructionstoensureproperinstallation.Formanyareasof construction,

thecodesstatethatroof coveringmustbeinstalledperthemanufacturersinstallationinstructions.

Instructionsshouldbeavailableonsitesothattheproperinstallationof theroof coveringcanbeachieved

andverified.Tofacilitatethetransferof thisinformation,itiscommontoseemanufacturersinstallation

requirementsprintedontheroof packagingitself.

NOTE

The FEMA MAT reports for 

hurricanes Charley (FEMA 

488), Ivan (FEMA 489), and 

Katrina (FEMA 549), along with 

FEMA 499 provide extensive 

and updated examples of roof 

covering best practices originally 

presented by FEMA in the 

Coastal Construction Manual 

(FEMA 55).
8-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

8 ROOF COVERINGS AND BEST PRACTICES

8.2.1 IRC Roof Covering Requirements 

General.TheIRCaddressesroof coveringrequirementsinseveral

areas.FireresistanceiscoveredinSectionR902andinsulationis

addressedinSectionR906,butthemajorityof therequirements

arepresentedinSectionR903andR904,whichaddressweather

protectionandmaterials,respectively.Requirementsforindividual

roof coveringsystems(e.g.,asphaltshingles,clayorconcretetile,etc.)

arelistedinSectionR905.

LoadandpressurerequirementsarecontainedinSectionR301.

SectionR301.2.1requiresthatroof coveringsresisttheC&Cloads

listedinTableR301.2(2)asafunctionof basicwindspeedandroof 

slope.TableR301.2(2)listspressuresforExposureBconditionswith

meanroof heightsof 30feetorless.Thepressuresmustbeadjusted

forotherheightsandexposuresbyfactorslistedinTableR301.2(3).

Thissectionprovidestherequiredloadsthatallcomponentsof a

roof system(suchasroof covering,roof deck,etc.)mustbedesigned

toresistthefullC&Cwindloads.Someexemptionsexistforair

permeablecladdingandotherroofingcomponents,providedthey

havebeencertifiedbytesting.

Roof DecksandUnderlayment.TheIRCgenerallyrequires

roofingtobeinstalledoncontinuoussheathing.Spacedsheathing

isallowedforsomemetalroofingsystems(specificallythoselisted

foruseonspacedsheathing)andforsomewoodandtileshingles

(inareaswhereanicebarrierisnotrequired).Buildingofficialsand

buildersshouldkeepinmindthatChapter9of theIRCpertains

toroof assembliesonlyanddoesnotaddressstructuralsystem

complianceforload-carryingsystemssuchasdiaphragms.Whilethe

useof spacedsheathingmaybeallowedbeneathsomeroof covering

systems,itmaynotsatisfystructuraldiaphragmandbracingrequirementscontainedelsewhereinthe

code.Aconsciousdecisionmustalsobemadewhetherspacedsheathingisanappropriatesystemtouse,

basedupontheroof slope.

WhencomplyingwiththeIRC,mostroofingsystemswillrequiretwolayersof underlaymentwhenthe

roof slopeisbetween2:12and4:12.Roof slopesgreaterthan4:12requireonlyonelayerof underlayment.

Underlaymentinhigh-windareas(i.e.,wherewindspeedsare110mphorgreater)mustbesecuredwith

corrosion-resistantfastenersspacednomorethan36inchesapart.

Asabest-practicesapproach,anaugmentedunderlaymentcanprovideaneffectivesecondary

roof barriertoreducewaterpenetrationintheeventthattheprimaryroof isdamagedbywindor

windbornedebris(seeFigure8-3).FEMA499,TechnicalFactSheetNo.19:Roof UnderlaymentforAsphalt

ShingleRoofs,providesguidanceonimprovingtheperformanceof roof systemsbyaugmenting

underlaymentinstallations.

NOTE

ASTM D 3161 tests samples 

of asphalt roofing shingles for 

exposure to high winds. This is 

accomplished by conditioning 

the samples (in order to seal 

their self-sealing strips) and then 

exposing them to an air stream. 

The conditioning involves 

heating the samples between 

135o F and 140o F for 16 hours. 

After conditioning, the samples 

are cooled to between 70o F and 

80o F and are then exposed to 

air-stream testing for 2 hours. 

The test involves blowing a 

stream of air across the test 

sample from three different 

directions. Shingles that restrain 

tabs from lifting, disengaging, or 

being torn loose pass the test.

ASTM D 3161 lists two types of 

asphalt shingles (Type I and Type 

II) and three wind speeds (Class 

A, D, and F). Type I shingles 

have self-sealing tabs; Type II 

shingles have interlocking tabs. 

Class A shingles pass the ASTM 

test with a simulated wind speed 

of 60 mph, Class D shingles 

pass the test at 90 mph, and 

Class F shingles pass at 110 

mph. While the IRC requires 

that shingles needing special 

fastening be considered Class F, 

the ASTM standard itself does 

not contain special 

fastening methods.
FEDERAL EMERGENCY MANAGEMENT AGENCY 8-5

ROOF COVERINGS AND BEST PRACTICES 8

AsphaltShingles.TheIRCpermitstheinstallationof asphaltshinglesoncontinuoussheathingfor

roofswithslopesaslowas2:12.Whenthiscoveringisinstalledonroofsslopedbetween2:12and4:12,

twolayersof underlaymentarerequired.Roofswithslopesgreaterthan4:12requireonlyonelayerof 

underlayment.SectionR301.2.1requiresthatasphaltshinglesbedesignedinaccordancewithSection

R905.2.6,whichpermitsasphaltshinglesclassifiedusingASTMD3161tobeinstalledinareaswithbasic

windspeedsbelow110mph.Areaswithwindspeedsof 110mphorhigherrequirespecialfastening

methods.Specialfasteningisalsorequiredforroof pitchesgreaterthan20:12.Specialfasteningrequires

shinglesthatareclassifiedusingASTM3161beconsideredClassF.Recommendationsontherequired

specialfastenersshouldbeattainedthroughtheshinglemanufacturer.

ASTMD7158isarelativelynewstandardforcertifyingasphalt

shingleswithself-sealingstripsforupliftresistance.Thetestcombines

physicaltesting(similartowind-tunneltesting)andananalytical

approachtodeterminewindspeedresistanceratings.During

certification,shinglesareprovidedwithpressuretapsthatallow

pressuremeasurementstobetakenatselectedlocations.Thetapsare

providedtomeasurepressuresatexposedportionsof theshingleas

wellasconcealedportionsof theshingle(i.e.,attheunderlayment).

Exposedandconcealedtapsareplacedbothaboveandbelowthe

self-sealingstrip.Theshingleassemblyisthenexposedtorelatively

lowwindspeeds(approximately35mph)andpressuremeasurements

todetermineexternalpressures(thoseabovetheshingle)andinternal

pressures(thoseattheunderlayment).Theselow-speedtestsprovide

externalandinternalpressurecoefficientsthatarecombined

intoanupliftcoefficient.Thecoefficientsareusedtodetermine

theupliftforcethateachshingletabwillexperienceforagivenwind

speed.Theshinglesarethenmechanicallytestedtodeterminetheir

tabsresistancetouplift.Shingleswithtabsstrongenoughtoresistthe

factoredupliftforceforagivenwindspeedarecertifiedforthatwind

speedbyclass.ASTMD7158liststhreeclassesof shingles:

NOTE

There are a few nuances of 

ASTM D 7158 that remain of 

interest to building officials, 

designers, and builders. These 

nuances include: building 

occupancy category (from ASCE 

7-05 Table 1-1), topographic 

effects, and mean roof height. 

The tab uplift calculations used 

in ASTM D 7158 are appropriate 

for Category I and Category II 

buildings (i.e., non-critical and 

non-essential facilities) that 

are less than 60 feet tall and 

located in areas not exposed 

to topographic wind effects 

(i.e., the ASCE 7-05 Chapter 

6 topographic effect factor Kzt

equals 1.0). If asphalt shingles 

are to be used on Category 

III or Category IV buildings, 

buildings higher than 60 feet 

tall, or buildings exposed to 

topographic effects, the shingle 

certification must use higher 

uplift forces. 

Figure 8-3.

Example of an augmented underlayment installation that helps 

provide a secondary barrier against 

water intrusion during a storm 

event. (Source: FEMA 488)
8-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

8 ROOF COVERINGS AND BEST PRACTICES

n Class

Dshinglespasstestswithbasicwindspeedsuptoandincluding90mph.

n Class

Gpasstestswithbasicwindspeedsuptoandincluding120mph.

n Class

Hpasstestswithbasicwindspeedsuptoandincluding150mph.

ThisnewstandardhasyettobereferencedbytheIRCorIBC,butisrecognizedbyICC-600.ASTM

D7158cannotbeusedtocertifyTypeIIshingles(i.e.,thosewithinterlockingtabs).TypeIIshingleswill

needtobetestedpercurrentASTMD3161tests.

Aspreviouslystated,manufacturersinstallationinstructionsneedtobefollowedtoensureproper

installationand,insomeinstances,codecompliance.Post-disasterMATinvestigationshavenotedthat

twoerrorsareoftenmadeinregardtotheshingleinstallationtechnique.Thesetwoerrorsoftenresultin

thefailureof theroof coveringduringhigh-windevents.

Thefirstcommoninstallationerrorconcernstheimproperinstallationof thestarterstrip

(seeFigure8-5).Forproperbondingof theself-sealingstrips,thestartercoursemustberotated180

degreesandthetabsmustbecutoff.If thetabsarenotremoved,theywillpreventtheself-sealingstrip

fromfunctioning.Figure8-4isanexampleof propershingleinstallationmethods.

Figure 8-4.

Example of proper shingle installation. (Source: FEMA 499)
FEDERAL EMERGENCY MANAGEMENT AGENCY 8-7

ROOF COVERINGS AND BEST PRACTICES 8

Thesecondcommoninstallationerroroccurswhenshinglesareinstalledinverticalsections.Whilethis

methodallowsrooferstotraversebackandforthacrosstheroof less,itmaynotallowforallof the

shinglestobeproperlynailed.Theendsof shinglesinstalledafterthefirstcolumnof shinglescan

likelynotbenailedwithoutmeticulouslyliftingthetabsof shinglesthathavealreadybeenfastened.This

procedure,calledraking,hasbeenidentifiedbyMATinvestigationsinnumerousfailuresinvolving

asphaltshingleroofsduringhigh-windeventsandisattributedtotheshingleshavingbeendamaged

andimproperlynailed.Figure8-6demonstratesanexampleof shinglefailureattributedtoraking.An

exampleof impropershingleinstallationisalsoshowninFigure8-7.

FEMA499,TechnicalFactSheetNo.20:AsphaltShingleRoofingforHigh-WindRegions,providesguidance

onasphaltshingleinstallations.Manyof therecommendationspresentedaresimilartothosedescribed

intheinstallationinstructionsprovidedbymanymanufacturers.

Figure 8-6.

Roof failures that resulted from 

asphalt shingles being installed in a 

raking fashion. (Source: FEMA 489)

Figure 8-7.

Loss of asphalt shingle roofing along 

hip. Best Practices approaches 

contained in Technical Fact Sheet 

No. 20 help prevent this mode 

of failure. (Source: FEMA 489)

Figure 8-5.

Roof failures that resulted from 

improper starter-strip installation.

(Source: FEMA 549)
8-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

8 ROOF COVERINGS AND BEST PRACTICES

ClayandConcreteTileRoofing.TheIRCpermitstheinstallationof concreteorclaytileonroofs

withslopesaslowas21/2:12.Tile-roofingunderlaymentrequirementsaresimilartoasphaltroofing

surfaces;twolayersof underlaymentarerequiredforlow-slopeapplicationsandadditionalfastening

fortheunderlaymentisneededforareaswithbasicwindspeedsof 110mphorgreater.Section905.3.7

requiresclayandconcreteroof tilestobeinstalledpermanufacturerinstructionswhenusedinareas

wherethebasicwindspeedis100mphorgreaterandinallareaswherethetilesareinstalledmorethan

40feetabovegrade.

FEMA(andotherentitiesthathaveconductedpost-disasterinvestigationssinceHurricaneAndrewstruck

Floridain1992)havenotedthattileroof coveringshavenotperformedwellduringseveralhigh-wind

events.Althoughperformanceof theseroof coveringsystemshasimprovedsinceHurricaneAndrew

(duelargelytobetterdesignandconstructionguidancefromthemanufacturers),roof coveringsystems

stillfrequentlyfailduringhurricanes.Theperformanceof mortar-settileroof systemscontinuesto

beverydependentuponthequalityof theinstallation.Thisinstallationmethodhasconsistentlybeen

observedduringMATinvestigationstonotperformaswellasothertileinstallationmethods.Tilesalso

remainvulnerabletobeingdamagedbywindbornedebrisbecausetheyareconsideredbrittlecoverings.

Whenclayorconcretetilesareimpactedbywindbornedebris,theycommonlybreakandleavethe

underlaymentexposedtohigh-windforcesitwasnotdesignedorconstructedtoresist(seeFigures8-8

and8-9).Thisconditionhasbeenobservedtoleadtoaprogressivefailureof theroof coveringacross

theroof surface.Also,oncedamaged,itisimportanttonotethatthetileshardscanbecomeairborne,

addingdebristothewindfield.Thisdebrismaycausedamagetothebuildingitself aswellasdamageto

downwindbuildings.

Figure 8-8.

Clay tile roof failure. The 

tiles were dislodged due 

to inadequate anchorage. 

(Source: FEMA 549)

Adequatedesign,testing,andinstallationcansignificantlyreducethepotentialfortilestobedislodged,

butvulnerabilitytodebrisdamageremains.FEMA499,TechnicalFactSheetNo.21:TileRoofingforHighWind

Areas,providesguidanceforinstallingtileroofingsystemswithincoastalareas.
FEDERAL EMERGENCY MANAGEMENT AGENCY 8-9

ROOF COVERINGS AND BEST PRACTICES 8

Figure 8-9.

Storm damage to a tile roof system. 

(Source: FEMA 488)

WoodShinglesandShakes.Sections905.7and905.8containtherequirementsforwoodshingleand

shakecoverings.Roofingcanbeinstalledonsolidorspacedsheathing,butsolidsheathingisrequired

whereicedamsorlowtemperaturesrequireaniceshield.Woodshakeinstallationsdifferfromwood

shingleinstallationsparticularlyintheirunderlaymentandrakeinstallations.Duetotheirregularsurface

of woodshakes,aninterlaymentlayerof 30-poundroofingfeltisrequiredtoimproveweathertightness.

Thisinterlaymentlayerisappliedbetweeneachcourse.

TheIRCdoesnotcontainprescriptiverequirementsforshinglesandshakesusedinhigh-windregions.

Althoughtheyarenotspecificallycited,shinglesandshakesmustsatisfythewind-loadingrequirements

of SectionR301.2.1.Inordertoverifyproperinstallationtechniques,usersof theseproductsshould

consultwiththeshingleorshakemanufacturerortheCedarShakeandShingleBureauforinstallation

instructionsrequiredtosatisfythewindloadrequirementsinareaswherethebasicwindspeedexceeds

100mph.

MetalShinglesandMetalRoofingPanels.SectionR905.4discussesmetalroofingshinglesand

SectionR905.10coversmetalroofingpanels.Theareaexposedtoweatherdistinguishesshinglesfrom

panels.Shinglesofferlessthan3squarefeetof weatherexposurepershingle;panelshaveexposuresof 3

squarefeetormore.

Metalshinglesandpanelscanbeinstalledonsolidsheathing,spacedsheathing,orpurlinsexceptwhere

theroof coveringisdesignedforspacedsupports.Aspreviouslystated,whenroof coveringsareinstalled

upondeckingthatisnotsolid,therequirementsof Chapter9of theIRCdonotapply,astheIRCdoes

notaddressroof diaphragms.Requirementsforstructuralstabilityneedtobecheckedforcompliance

withotherportionsof thecode.Forthesesystems,bracingwillneedtobeinstalledtoprovidethecoderequired

structuralstability(describedbyengineersanddesignersasdiaphragmaction).Anexception

inthecodeisprovidedwhenthemetalroof coveringisdesignedtoactasastructuraldiaphragmand

whenitisinstalledonspacedsupportsorspacedsheathing.
8-10 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

8 ROOF COVERINGS AND BEST PRACTICES

TheIRCstatesthattheminimumroof slopeformetalshinglesis3:12.Theminimumslopeformetal

panelsdependsuponthemethodsusedtojointhepanels.Lapped,non-solderedpanelshavethesame

sloperequirementsasmetalshinglesandcanbeusedonroof deckswithslopesaslowas3:12.Lapped

panelsjoinedwithanappliedlapsealantcanbeusedforslopesaslowas:12.Standing-seamroofing

canbeusedonroof surfaceswithslopesaslowas:12.TableR905.10.3(1)listsmaterialrequirements

formetalroof panels(theserequirementsalsoapplytometalroof shingles).

TheIBCdoesnotincludeprescriptivefasteningdesignsformetalshinglesandmetalroof panels.While

theIRCdoesnotspecificallyaddresstheuseof metalshinglesandmetalroof panelsinhigh-windareas,

themanufacturershouldbeconsultedtodeterminefasteningandotherinstallationrequirementsfor

basicwindspeedsexceeding100mph.ItisnotablethatMATinvestigationsfrom1998to2008continue

toobservegoodperformanceof metal-panelroof systems.

Roof CoveringsforLow-Sloped(<:12)Roofs.Modifiedbitumenroofing,thermoset,and

thermoplasticsingle-plyareapprovedfornearlyflatroofs.IRCSectionsR905.11,R905.12,andR905.13

outlinetherequirementsforthesetypesof roof covering.

Therequirementsfocusonmaterialspecificationsandapplicationof theroof covering.Modified

bitumenmembranesaretypicallyfullyadheredand,wheninstalledonaproperlyconstructedroof deck,

canperformwellduringhigh-windevents.Single-plysystems,however,havebeenobservedtoperform

poorlywhenexposedtohighwinds,particularlyif thesesystemsarenotfullyadhered.Whenusedin

areaswherethebasicwindspeedexceeds100mph,single-plysystemsshouldbefullyadhered.

Withallmembranesystems,caremustbetakenalongtheedgeandcornerzonesof theroof,wherewind

turbulencecreateshighlocalizedupliftpressures.Post-eventMATassessmentshavedeterminedthat

roofingfailurescommonlybeginattheedgesorcornersof theroof,wheninsufficientattentionisgiven

tofastening,flashing,andcoping.

8.2.2 IBC Roof Covering Requirements

TheIBCrequirementsforroof coveringsaresimilartothoseincludedintheIRC.LiketheIRC,

muchemphasisisgiventoweatherprotection.However,emphasisisalsogiventothefireratingsof 

roof coverings.

Section1504.1statesthattheroof coveringsmustbedesignedtoresistthewindloadrequirementsof 

Section1504andChapter16.Chapter16statesthatthewindloadrequirementsforroof coverings

unlessspecifiedotherwisearetocomplywithwindpressuresbaseduponASCE7.

Therequirementsforinstallationof asphaltshinglesintheIBCarethesamerequirementsasthose

containedintheIRC.TheIBCrequirementsarelistedinSection1540.1.1.Clayandconcretetilesare

treatedsimilarlybutanalternativeprocedurefordeterminingandcertifyingwindresistanceisallowed

bySection1504.2.Thealternativeprocedureissimilartothenewproceduresof ASTMD7158,which

aredescribedearlierinthischapterandspecifiedforself-sealing,asphaltshingles.Liketheproceduresof 

ASTMD7158,thealternativeproceduredoesnotaddresscriticaloressentialfacilitiesanditsapplicability

islimitedtobuildings60feettallorlower.
FEDERAL EMERGENCY MANAGEMENT AGENCY 8-11

ROOF COVERINGS AND BEST PRACTICES 8

Thedeckandunderlaymentrequirementsof theIBCaresimilartothosecontainedintheIRC.TheIBC

doesexempticemembranerequirementsforunderlaymentwhenusedondetachedaccessorybuildings

thatarenotheated.

8.2.3 IBC Requirements for Aggregate Ballast (Gravel and Stone) Roof Coverings

Highwindscandislodgeaggregateballast(e.g.,gravelandstone)fromroofs.Oncedislodged,theroof 

ballastcanbecomeairbornewithsufficientenergytodamagedownwindbuildings.Buildingswith

unprotectedglazingareparticularlyvulnerable.

Since1972,researchershavebeenobservingdamagestoglazingonhigh-risebuildingslocatednextto

orincloseproximitytostructureswithstoneorgravelroofs.Thesedamageshavebeenattributedto

theaggregatebeingdislodgedandblownintotheglazingof theadjacentbuilding.FEMAobserved

severalinstancesof thisbehaviorinNewOrleansafterHurricaneKatrina.(SeeFEMA549andFEMA

543foradditionalinformation.)The2000IBCandASCE7-95identifiedwindhazardareasknownas

windbornedebrisregions.Sincethen,theseregionshavebeenmappedtodelineateareasnearthecoast

wherewindbornedebrisissuescanaffectnotonlyglazing,butthestructuralintegrityof thebuilding,

aswell.Subsequentversionsof thecodehaveincludedspecificrequirementsthataddressmeasuresto

mitigatedamages.

IBCSection1504.8providesrequirementsforaggregateballastonroof systems.Thesectionprecludes

theuseof aggregateballastonroofsinhurricane-proneregions(i.e.,areaswherethebasicwindspeed

is120mphorhigher).Inareaswithalowerbasicwindspeed,Table1504.8placesrestrictionsuponthe

exposurecategoriesforaggregateballastatwindspeedslessthan120mphandlimitsontheheightsof 

roofsthatuseaggregateballastforbuildingssitedinhigherexposurecategories.Forexample,whena

buildingissitedinExposureCareaswherethebasicwindspeedis85mph,Table1504.8prohibitsthe

useof aggregatesurfacecoveringswhenthemeanroof heightexceeds60feet.

ThevalueslistedinTable1504.8of theIBCdenotethemaximumallowablemeanroof heightpermitted

forbuildingswithgravelorstoneroofsinareasoutsideof ahurricane-proneregion.Presently,thistable

doesnottakeintoaccountthesizeordensityof thegravelorstone.Inaddition,itdoesnotaccountforthe

effectof roof parapets,whichcansignificantlyaugmenttheturbulence.Recentanecdotalinformation

suggeststhistableshouldtakeintoaccounttheseimportantphenomena.However,moreresearchtests

andquantifiableresultsneedtobeconductedbeforeacoderevisioncanbeconsidered.

Section1504.4of theIBCrequireslow-slopeaggregate-surfaceroof systemstocomplywithANSI/SPRI

WindDesignStandardforBallastedSingle-PlyMembraneRoofing(RP-4).RP-4containsprovisionsthatallow

aggregateballastedsystemstobeinstalledwithinsomewindbornedebrisregions.Therequirements

dependuponanumberof factorsincludingthebasicwindspeed,exposure,presenceandheightof 

parapets,andmethodbywhichtheaggregateissecured.
8-12 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

8 ROOF COVERINGS AND BEST PRACTICES

8.2.4 Roof Vents

Roof ventsposeadesignandconstructionchallengebecausetheyarelocatedwheretheroof covering

androof sheathingmaybeseparated.If theventsarenotproperlyinstalled,watermayfinditsway

beneaththeroof covering,causingroof coveringfailuresor(potentially)totalroof systemfailures.The

FloridaDepartmentof CommunityAffairs(DCA)Websitecontainsrecommendationstoimprovethe

performanceof ridgevents,off-ridgevents,andturbinevents.Theseandotherrecommendationsare

availableathttp://www.floridadisaster.org/mitigation/rcmp/hrg:

n The

DCAWebsitesuggestsinspectingoff-ridgeventstoseeif theyareloose.

n Check

forthepresenceof fastenersanchoringturbinestotheroundductthatpenetratestheroof.

n Check

tomakesurethattheductissecure.

n Check

aroundallpipesthatpenetratetheroof andensurethattheflashingaroundthepipeissealedto

thepipewithoutanygapsorcracks.

Inaddition,itisimportanttodeterminethespacingandsizeof nailsorscrewsusedtoholddownridge

vents,off-ridgeatticvents,turbines,andanykitchenorbathroomventsthatprotrudethroughtheroof.

Thisinspectionisperformedinordertodetermineif theappropriatenailswereusedandif theywere

driveninthecorrectlocations.Manytimesroofersusethesamelengthnailstofastentheseelementsas

theyusetofastentheshingles.Inmostsituations,alongernailwillberequiredforadequateanchorageof 

theseitems.If longernailsareusedandtheystickfarenoughthroughtheroof deck,theanchoragecan

beimprovedbyclinchingthenails(i.e.,usingahammertobendnailheadsover)frominsidetheattic.

8.3 Re-Roofing Code Requirements & Best Practices

Section1510of theIBCandSection907of theIRCaddressroof coveringreplacement.TheIBCrefers

tothisasre-roofingtheIRCasre-covering.

TheIRCandtheIBCgenerallyrequirere-roofingtomeettherequirementsof newroof installations.

Onenotableexceptiontotheserequirementsconcernstheslopeof theroof.Re-roofingdoesnotneedto

meetthesloperequirementsforanewroof if thatroof providespositivedrainage.

IBCSection1510.3requiresoldroofingtoberemovedbeforeinstallinganewroofcovering,asstatedbelow:

1. Where

theexistingroof orroof coveringiswatersoakedorhasdeterioratedtothepointthattheexistingroof orroof 

coveringisnotadequateasabaseforadditionalroofing.

2. Where

theexistingroof coveringiswoodshake,slate,clay,cement,orasbestos-cementtile.

3. Where

theexistingroof hastwoormoreapplicationsof anytypeof roof covering.

Thereareexceptionstotear-off requirementsforcompleteandseparateroof systemsthatcantransmit

roof loadsdirectlytothebuildingsstructuralsystem.Theserequirementsareapplicabletometal
FEDERAL EMERGENCY MANAGEMENT AGENCY 8-13

ROOF COVERINGS AND BEST PRACTICES 8

panel,metalshingle,andconcreteandclaytileroof coveringsoverwoodshakeroofs,aswellasfornew

roofingoveranexistingsprayedpolyurethanefoamsystem.

Somestate-specificcodescontainrequirementsforre-roofing.Forexample,theFloridaBuildingCode

(FBC)hasmorestringentrequirementsforroof coveringswithinitsHighVelocityHurricaneZone

(HVHZ)thanarerequiredforotherportionsof thestate.

TheHVHZre-roofingsectionrequiresagreaterlevelof inspectionandrestrictionswhenre-roofing.Reroofing

withouttear-off of theexistingroof coveringisallowedbutapplicationsarelimited.Forexample,

FBCsection1521.17allowsasphaltshinglestobeinstalledoveranexistinglayerof shinglesonlywhen

notmorethan

1

/8inchdifferenceinlevelof theexistingshinglematerialexists.

Are-roofingprojectprovidesaperfectopportunitytoimproveexistingbuildings.Whenaroof covering

isremoved,accessiscreatedtoroof deckingandotherbuildingcomponents(particularlyfasteners)that

typicallyremainconcealedandinaccessibleotherwise.Duringtheseprojects,theloadpathfromthetop

of thewalltotheroof deckmaybeupgraded,newconnectorsmaybeinstalled,andnewflashingand

underlaymentmaybeinstalled.Eventhoughmanyof thesebestpracticesarenotrequiredbythecodes,

anumberof themshouldbecompletedduringare-roofingeffort.Thefollowinglistappliestomanyroof 

systems,butisprimarilygearedtoroof systemstypicallyfoundonone-andtwo-familydwellings:

n Whenever

aroof coveringistobereplaced,acompletetear-off shouldbeconsideredandshouldbe

completedunlessenvironmentalorotherissuesmakeremovalprohibitive.

n Once

theroof coveringisremoved,theentireroof sheathingshouldbeinspectedandalldamaged

sectionsof roof sheathingshouldbereplaced.If thesheathingthicknessdoesnotconformtocurrent

codesandstandards,thesheathingshouldbereplacedandproperfastenersshouldbeinstalled.Roofsheathing

fastenersinthehigh-windpressurezonesalongroof edgesandcornersshouldbegiven

particularattention.

n Portions

of theroof sheathingmayalsoberemovedtoprovideaccesstotheconnectionsbetween

theroof framingandthewallsbelow.Connectionsneededtocomplywithcurrentcodesfornew

constructionshouldbeinstalled.

n A

secondaryroof barriershouldbeinstalledforenhancedwater-intrusionprotection.Wheninstalling

aroof underlaymentasasecondarybarrier,itisimportanttorememberthattherearemultiple

successfulmethodsof installation.FEMA499providesguidanceonselectingandinstallingsecondary

roof barriers.

n When

re-roofing,choosearoof coveringappropriateforthebasicwindspeedwithinthearea.Selecta

roof coveringratedforahigherwindspeed,if budgetallows.

Recent legislative rules issued by the State of Florida promote roofing mitigation through Rule 9B-3.0475. While 

this rule applies only to residential structures and has restrictions per monetary values, it promotes efforts to 

strengthen the connections of residential buildings and other mitigation efforts during re-roofing. After connections 

have been strengthened to meet or exceed the latest effective code, the removed sheathing should be properly 

reinstalled according to the code. It is paramount to ensure that buildings which may experience high-wind events 

have the roof decking properly secured to the framing.

FEDERAL EMERGENCY MANAGEMENT AGENCY 9-1

EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES 9

Exterior Cladding Components 

and Best Practices

9.1 Introduction

Chapter

7presentedinformationonthebuildingstructurespecificallyroof deckingandwall

systems.Chapter8presentedinformationonroofingmaterialsandcoverings.Thischapterdiscusses

exteriorwallcoverings,alsoknownascladding.Asinpreviouschapters,theinformationherein

willpresentspecificbuildingcoderequirementsfirst,followedbyguidance(orindustrybestpractices)

forvariouscladdingmaterials.Whenpossible,adiscussionwillbeincludedonhowthesesystemsmay

proveresistanttothosenaturalhazardsthatareprevalentincoastalenvironments.Thediscussionof the

buildingenvelopewillconcludeinChapter10withthepresentationof designcriteriaandbestpractices

relatedtodoorsandwindows.

Thebuildingenvelopeincludes:cladding,roof coverings,glazing,exteriorwalls,doorassemblies,window

assemblies,skylightassemblies,andothercomponentsenclosingthebuilding.Incoastalareas,thefloorsof 

buildingselevatedonopenfoundationsmayalsobeconsideredpartof theenvelope.Unlikeconstruction

thatoccurswithininlandareas,coastalconstructionmustbedesignedandbuilttowithstandhigh-wind

events(whichcantriggerwindbornedebris),floodevents(possiblyincludingwaveeffects),andother

issues,suchasthecorrosionof fastenersandconnectors.

Thebuildingenvelopecanbeoneof theweakestandmostsusceptiblecomponentsof abuilding.Farmore

commonthanstructuralfailures,envelopefailuresoftenleadtowaterintrusionandprogressiveenvelope

failuresoveralargerpartof thebuilding.Envelopefailurestypicallyinvolvingafailedcomponentthat

isitself smallinmagnitudemayresultindisproportionatelygreaterbuildingdamage(andassociated

repaircosts)thanthatcausedbytheinitialbreachintheenvelope.

Thedurabilityof thestructuresenvelopeisdependentuponthetypeof materialsused,thedesign,and

themethodof installation.Buildingenvelopecomponentshavealsobeenobservedtobethepredominant

sourceof windbornemissiles,asgeneratedfromdamagedbuildings.Closedesignattentionshouldbe

giventobuildingswithinspecialwindregionsandwithinareaswherethebasicwindspeedexceeds90

mph(in3-secondgusts).Technicalguidanceforimprovingtheperformanceof buildingenvelopeelements

andsystemswithincoastalareascanbefoundinFEMA55andinMATandBPATreports.FEMA499

TechnicalFactSheetsalsoprovidespecificinformationonexteriorcladdingmaterial,installation,and

generalbest-practiceguidanceforcoastalareas.

9.2 Exterior Wall Coverings and Claddings

Highwindsandfloodingarenaturalhazardsthatcancauseseveredamagetoexteriorwallsystems.

Seismiceventscanalsodamageheavywallsystemsorcoveringssuchasbrickveneer.Largehailhasbeen

reportedtodamagewalls,althoughwidespreaddamageisuncommon.
9-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

9 EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES

Avarietyof systemscanbeusedforexteriorwallconstructionor

cladding.Thefollowingwallcoveringsarecommonlyusedover

wood-frameandmasonryconstruction:aluminumsiding,cementfiber

panelsorsiding,exteriorinsulatingfinishingsystem(EIFS),

stucco,vinyl,sawn-woodsiding,andwood-panelsiding.Eachof 

thesewallcoveringscanexhibitvaryingperformancecharacteristics,

includingthoserelatedtopermeability.Whilematerialsuchasvinyl

isnon-permeable,whenusedasasidingmaterialitisdesignedto

resistbutnotpreventwaterintrusion.Concreteandmasonry

wallsfunctiondifferentlythanframedandsurfacedwalls.Whileframedwallsaredesignedtoshedwater;

whennotsurfacedwithcladdingmaterials,concreteandmasonryconstructionisdesignedtoabsorb

waterandreleaseitthroughevaporation.FEMA499,TechnicalFactSheetNo.8:CoastalBuildingMaterials

containsadditionalinformationoncoastalbuildingmaterialsandbestpracticesforselectingandusing

differentmaterials.

Afterrecenthurricanes,MATreportshavedocumentedthatwallcoveringsrippedfromhousescan

becomewindbornedebris,easilycapableof damagingotherstructures.Thesereportsalsoshowthat

pressurizationanddamagetotheinteriorcontentsof buildingsisoftentheresultof aprogressivefailure

of theexteriorwallcovering.Highwindsarethemostcommoncauseof theseinitialfailures.While

compliancewithcurrentcodesandstandardswillmakebuildingsmuchlessvulnerabletowaterentryand

damagefromdebrisimpacts,someactions(consideredcodeplusorbestpractices)havebeenshownto

improvebuilding-envelopeperformance.Thoseconstructionpracticesexceedcodeminimumsandtheir

useisoftenwarrantedwhentryingtoachieveimprovedprotectionwithinacoastalenvironment.

9.2.1 Designing for Wind Forces

Exteriorwallsmustbedesignedandbuilttowithstandcode-specified

basic(design)windspeeds;thisincludesbothMWFRSandC&C

loads.Basicwindspeedscanbefoundusingwindmapsfromvarious

codesandstandards(ASCE-7-05containsawindmapusedbythe

IBC,IRC,andmostcontemporaryconstructionstandards).Incoastal

areas,windspeedsaregenerallygreater,sotheeffectsof highwinds

onexteriorcladdingareaprimaryconcernincoastalconstruction.

Winddesignof exteriorwallcoveringsonresidentialstructurescan

beperformedusingprescriptiveorperformance-basedcodes.The

prescriptivesolutionsinboththeIBCandtheIRCconcernareas

wherethebasicwindspeedislessthan110mph(orlessthan100mphinhurricane-proneregions).

Inareaswherethebasicwindspeedis110mphorgreater(or100mphorgreaterinhurricane-prone

regions),theprescriptivesolutionsof theIBCandIRCdonotapply.Forthoseareas,SectionR301.2.1

referenceshigh-windstandardssuchasAF&PAsWFCM,theICC-600,andtheAISIStandardforColdFormed

SteelFraming:PrescriptiveMethodforOne-andTwo-FamilyDwellings.Asanalternativetoprescriptive

designs(andasrequiredforbuildingsthatfalloutsideof therangeof prescriptivesolutions),buildingscan

beengineeredtomeettherequirementsof theIBC,whichrequiresthatbuildingcomponentsresistloads

inaccordancewithASCE7-05.

NOTE

ASCE 7-05, Section 6.1.4.2, 

on components and cladding 

(C&C), requires that the 

minimum design pressure 

for C&C shall be +/- 10 psf 

regardless of the basic wind 

speed at a site.

NOTE

Another solution still being 

developed involves airpermeable wall coverings. The 

discussion of air-permeable roof 

coverings presented in Chapter 

8 also applies to air-permeable 

wall coverings, such as siding. 

Research on special-pressure 

coefficients for air-permeable 

wall claddings need to be 

conducted before new code 

requirements can be developed. 
FEDERAL EMERGENCY MANAGEMENT AGENCY 9-3

EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES 9

ManyjurisdictionsarestillusingtheSSTD10andfollowingitsprescriptiveguidanceforthemainwind

forceresistingsystem(MWFRS)of thebuildingenvelope.Althoughthisisaveryhelpfulstandard,this

detailforC&Cdesignislimited.TheICC-600providesmoredetailedguidanceonthebuildingenvelope

andaddressesboththeMWFRSandtheC&C.

IBCRequirements

Wall-coveringrequirementsarecoveredprimarilyinChapter14of theIBC.Variousrequirementsare

containedinSection1405.1(general),Section1405.2(weatherprotection),andSection1405.3(flashing).

Requirementsforspecificwall-coveringsystemsarecontainedinsubsequentsections:Section1405.5

(woodveneers),Sections1405.5and1405.9(anchoredandadheredmasonry),Section1405.6(stone

veneers),Section1405.7(slab-typeveneers),Section1405.8(terracottaveneers),andSection1405.10

(metalveneers).Someof themorecommonexteriorcladdingmaterialsincludevinylsiding(Section

1405.13)andfiber-cementsiding(Section1405.17).

Eachsectionincludesrequirementsthatareuniquetothatstyleof cladding.Forexample,heaviercladding

materials(suchasmasonryorstone)haveadditionalseismicrequirementsidentified.Lightermaterials,

suchasvinylsiding,mayhaveadditionalrequirementsconcerningbackingmaterialandfastening.

IRCRequirements

LiketheIBC,theIRCcontainsgeneralrequirementsforallexteriorsystems,aswellasmorespecific

requirementsforindividualwallcoveringsystems,whicharecontainedinothersections.SectionR703.1

containsgeneralrequirementsforallsystems.Thesegeneralrequirementsinclude:providingthebuilding

withaweather-resistantenvelope,provingflashing(withsomeexceptions),preventingtheaccumulation

of waterwithinthewall,andprotectionsfromcondensation.Water-resistivebarriersrequirementsare

containedinSectionR703.2andgeneralrequirementsforwallsystemattachmentsareoutlinedin

SectionR703.4.

ExceptionsexistforSectionR703.1requirementsthatpertaintoconcreteandmasonryconstruction

(thatarelessvulnerabletowaterdamage)andtestedsystemsthatprovidethesameperformanceasthe

systemsprescribedinSectionR703withoutusingthespecificcomponentsrequiredinSectionR703.1.

Subsequentsectionsaddressspecificexteriorcoverings:SectionR703.3(wood,hardboard,andwood

structuralpanelsiding),SectionR703.5(woodshakesandshingles),SectionR703.6(plasterorstucco),

SectionR703.7(stoneandmasonryveneer),SectionR703.9(ExteriorInsulationFinishingSystem,

orEIFS),SectionsR703.9.1andR703.9.2(specificEIFSrequirementsforwater-resistivebarrierand

flashing),SectionR703.10(fiber-cementsiding),andSectionR703.11(vinylsiding).

MoistureBarriers

TheIBCandIRCrecognizethreemethodsof weatherprotectionforwalls:1)wallscanbeconstructed

withflashingandwater-resistantbarriers(WRB)(seeFigures9-1and9-2),2)wallscanbeconstructedwith

anexteriorwallsystemwhichhasbeencertifiedtoresistwind-drivenrain,or3)wallscanbeconstructed

withconcreteormasonry.
9-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

9 EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES

Thefirstmethod(whichisoftenusedwithwoodsiding,cementitiousstucco,andbrickveneer)functions

topreventwaterfromenteringthecladdingandprovidesdrainagepathsforwaterthatdoesenter.The

secondmethod(whichincludesmanyEIFS,curtainwalls,andotherspecializedsystems)strivestoprevent

waterfromenteringthecladdingandmayormaynothavedrainageprovisionstoaddresswaterthatdoes

enter.Thethirdmethodutilizesweatherprotection(usingconcreteormasonrywalls),whichallowswater

tobeabsorbedbythebuildingandthenbereleasedtotheexteriororinteriorthroughevaporation.

Thefirsttwomethodsarereferredtoasbarriermethods,withthefirstmethodservingasatraditional

barriermethod.ThegeneralrequirementssetforthbytheIBC(Section1403.2)andIRC(SectionR703.1)

statethatabuildingmusthaveaweather-resistantexteriorwallenvelope(unlessthatbuildingisconstructed

withaconcreteormasonrywallsystemthatmeetsIBCandIRCrequirements).Alternatively,thewall

envelopemustbedemonstratedtoresistwind-drivenrainthroughtestingof theenvelope(including

joints,penetrations,andintersectionsconstructedof dissimilarmaterials)inaccordancewithASTME

331andinaccordancewiththeconditionslistedinthesectionsof thestandards.Forprotectionoverstuds

orsheathing,theIBCrequiresaminimumof onelayerof No.15asphaltfelt,complyingwithASTM

D226forType1feltorotherapprovedmaterials,shallbeattachedtothestudsorsheathing.TheIRC

statesthesamestipulations,butgoesfurthertosaythatsuchfeltormaterialshallbeappliedhorizontally,

withtheupperlayerlapped2inchesoverthelowerlayerand6inchesatverticalendjoints.

Traditionalbarriersystemsfunctionbestwhenanairspaceexistsbetweentheexteriorcladdingandthe

WRB.ThinfurringstripscanbeinstalledbetweenlappedsidingandtheWRBtocreatethisairspace.

SystemsthatincorporateadrainagegapintotheWRBarealsoavailable.Whenbrickveneerisused,

mortarshouldnotfilltheairgapbetweentheveneerandtheWRB,eventhoughdoingsoisallowed

bycode.

Figure 9-1 and 9-2.

Examples of moisture barrier systems. (Source: FEMA 549)
FEDERAL EMERGENCY MANAGEMENT AGENCY 9-5

EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES 9

Inareaswherethedurationof severeorwind-drivenrainsisbrief,theweather-protectionmethods

allowedbytheIBCandIRCshouldperformsatisfactorily.Incoastalareas,however,rainscanbe

prolonged,severe,andfrequentlydrivenbyhighwinds.Prolongedwind-drivenrainscanoverwhelm

thewater-storagecapacityof masssystems(i.e.,concreteormasonrystructures)anddrivingwindscan

createpressuresthatexceedthoseof testedsystems.Theuseof traditionalbarriersystemswithflashings

anddrainagepathsshouldbeconsideredwithincoastalareas.Testedsystemsareappropriatetouseif 

theyhavebeencertifiedforwindspeedsandrainconditionspresentwithincoastalenvironments.Mass

systemswillfunctionbestwhenmultiplelayersof moistureprotectionareimplemented.Forexample,if 

thebuildingskinutilizesconcreteormasonry,thebuildingwillwithstandthesignificantwindforcesof a

hurricane,butwilllikelybeoversaturatedbythesustainedheavyrainsthatalsoaccompanyhurricanes.

Thiswillcausewaterdamageandassociatedproblemsinthebuilding(e.g.,mold).Toeffectivelycontrol

waterintrusion,thelayersof moisturecontrolshouldbeincreasedbyaddingsidingovertheconcreteor

masonrywallsanddesigningproperdrainagepathsbetweenthetwomaterials.

If sidingisused,properlappingmustbeensuredtomaximizemoisturecontrol(seeFigure9-3).Capillary

actioncauseswatertotravelinalldirectionsandallowswatertoinfiltratesidingif lappingisinstalled

incorrectly.Itisimportantthatsidingisspacedwithenoughlapdistancetolimitwaterintrusion.

Manufacturerspecificationsshouldalwaysbefollowedduringinstallation;forimprovedperformance,

consultwithadesignprofessionalforalongerlapdistance.MoreinformationcanbefoundonFEMA

499,TechnicalFactSheetNo.9:MoistureBarrierSystems.

Theuseof asecondarylayerof protectionagainstwind-drivenwaterinfiltration(e.g.,anair-barrierfilm)

isrecommendedunderneathwallcoverings.Designersshouldspecifythathorizontallapsbeinstalledso

thatwaterisallowedtodrainfromthewall(i.e.,thetopsheetshouldlapoverthebottomsheetinorder

toallowwaterrunningdownthesheetstoremainontheirouterface).Thebottomof thesecondary

protectionneedstobedetailedtoallowdrainage.

Gravity moves

water downward.

Do not count on

sealant to substitute 

for proper lapping.

Wind and capillary

action can move water 

in any direction.

Laps should never 

cause water flowing 

downward to “buck” 

over seams.

Proper lap didstance 

is the key to limiting

water instrusion caused

by wind and capillary 

action. Always follow 

manufacturer’s lap

specifications or, if a 

greaer lap is specified 

by the designer, follow

designer’s requirements.

Figure 9-3.

Proper siding lapping to prevent moisture penetration. (Source: FEMA 499)
9-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

9 EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES

9.2.2 Flashings

FlashingisrequiredbytheIBC(Section1405.3)andIRC(SectionR703.8)inordertopreventmoisture

fromenteringthewallsystemortoredirectittotheexterior.Flashingistypicallylocatedatexterior

doorandwindowassembliesandatanypenetrations,projections,orterminationsintheexteriorof 

thebuilding.Thepoorperformanceof flashing,resultinginthelossof water-intrusionprotection,isa

commonprobleminmanycoastalhomes.Inareasthatfrequentlyexperiencestrongwinds,enhanced

flashingdetailsarerecommendedtoprovidebetterprotectionagainstwind-drivenrain.Enhancements

includeflashingsthathaveextra-longflanges,andtheuseof sealantandtapes.Generalguidanceis

offeredherein,butitisrecommendedthatdesignersalsoattempttodeterminewhattypeof flashing

detailshavesuccessfullybeenusedwithintheareawheretheresidencewillbeconstructed.

Flashingdesignshouldrecognizethatwind-drivenwatercanbepushedvertically.Theheighttowhich

watercanbepushedincreaseswithwindspeed.Watercanalsomigrateverticallyandhorizontallyby

capillaryactionbetweenlayersof materials(e.g.,betweenaflashingflangeandhousewrap).

9.3 Exterior Covering and Best Practices

Whiletheexteriorsof homesconstructedtocurrentbuildingcodesgenerallyperformwellincoastal

environments,actionsthatgobeyondcode-minimumsoftenimprovebuildingperformance.Code-plus

orbest-practicesapproachesforcommonexterior-coveringmaterialsarepresentedinthefollowing

sections.Withtheevolutionof modernbuildingcodes,approachesthathaveconsistentlyresultedingood

performancehavebeenincorporatedintocodesandarenowrequired.

Flashingguidancespecifictoroof/wallconnections,windows,anddoorsisprovidedhere.Formore

information,seeFEMA499,TechnicalFactSheetsNo.22:WindowandDoorInstallationandNo.24:Roofto-Wall

andDeck-to-WallFlashing.

Roof/wallflashing.Specifically,roof androof-to-wallflashingisaddressedinSection1503.2of the

IBCandSectionR903.2of theIRC.Figure9-4illustratesagoodroof/wallflashingdetailthatiscodecompliant

andincludesbestpracticesrecommendedinthissection.Itrecommendsthatwhereenhanced

protectionisdesiredabovethecodeminimums,usestepflashingthathasaverticallegthatis2to4inches

longerthannormal.(ThisdetailhasbeenusedsuccessfullybyabuilderontheDelawarecoast.)

Alternativelyanotherrecommendation(orforamoreconservativedesign,inadditiontothelongleg),

suggeststapingthetopof theverticalflashingtothewallsheathingwith4-inch-wideself-adheringmodified

bitumenroof tape.(Applyabout1inchof tapeonthemetalflashing,and3inchesonthesheathing.)

Itisalsoconsideredgoodpracticetoextendthehousewrapovertheflashinginthenormalfashion.Itis

importantnottosealthehousewraptotheflashing;if waterreachesthehousewraphigherupthewall,

thatmoistureneedstobeabletodrainoutatthebottomof thewall.
FEDERAL EMERGENCY MANAGEMENT AGENCY 9-7

EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES 9

Window/DoorFlashings.Forwindowswithnailingflanges,itisconsideredgoodpracticetoapply

agenerousbeadof butylsealanttothewallsheathingbeforesettingthewindow.Thenplacethesealant

inwardof thefasteners.Atsheathingjoints,placesealantoverthejoint,fromthewindowopeningout

pasttheflange.Placethehousewrapoverthehead-trimflashing,andtapetheflangetothehousewrap

withducttapeormodifiedbitumenroof tape.ArecommendedflashingdetailisshowninFigure9-5.

Conceptually,theexteriorsidingshouldnotbethoughtof astheonlybarriertowaterintrusion.The

housewrap(typicallyrequiredundermostsidings),flashings,andunderlaymentmustbeusedtoshedand

directwaterawayfromopeningsinthebuildingenvelope.Theoverridingprincipleof successfulwater

diversionistoinstallthelayersof buildingmaterialscorrectlysothatwatercannotgetbehindanyone

layerandintoanopening.

Housewarp or building paper

(do not attach to roof tape)

4”-wide (minimum) Self-adhering

modified bitumen foor tape

Shingles Wall sheathing

Step flashing with 2”

to 4” longer vertical

leg than normal

Vertical Leg

Roof sheathing

Underlayment

Note: Stop housewarp

or building paper

approximately 11

/2”

above shingles.

Figure 9-4.

Roof flashing. (Source: FEMA 499) 

Figure 9-5.

Window flashing details. 

WINDOW DETAIL

WINDOW FLASHING

& WATERPROOFING DETAIL

BARRIER

STRIP

BARRIER

STRIP

BARRIER

STRIP

WINDOW

FRAME

SHEATHING

FLASHING

MOISTURE

BARRIER

HEAD TRIM

EXTERIOR CLADDING NOT

SHOWN FOR CLARITY
9-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

9 EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES

VinylSiding.Vinylsidingcansuccessfullyprotecthomesandfunctionadequatelywithinacoastal

environment,if properlyinstalled.Designersandbuildersshouldchoosesidingthatisratedforhigh

winds.Theseproductstypicallyhaveanenhancednailinghemandaresometimesmadefromthicker

vinyl.Figures9-6,9-7,and9-8providedetailsandillustrateproperinstallationtechniquesforvinylsiding.

Thick,rigidpanelsprovidegreaterwindresistance,withstanddents,andlieflatterandstraighteragainst

thewall.Panelsthathaveperformedwellpossessanoptimumthicknessrangingfrom0.040inchto0.048

inch,dependinguponthestyleanddesign.Also,manyvinyl-sidingsystemsmustbeinstalledoversolid

sheathingtoperformattheirratedwindspeedwithoutdamageorfailure.Manufacturersinstallation

instructionsshouldcontainthisinformationandotherrequirements.Moreinformationcanbefoundin

FEMA499,TechnicalFactSheetNo.25:SidingInstallationandConnectors.

High-wind siding Standard siding

Double

nailing 

hem

Greater locking 

area

Thicker vinyl

Figure 9-6.

Comparison of typical high-wind 

siding verses standard siding. 

(Source: FEMA 499)

Yes No

Figure 9-7.

The center of the nailing slot is 

the proper fastener location. 

(Source: FEMA 499) 1/32”

(about the 

thickness of

a dime) Figure 9-8.

Proper fastener clearance. 

(Source: FEMA 499)

AfterHurricaneKatrina,theFEMAMATReport(FEMA549)concludedthat,whilemuchof thevinyl

sidingdamagefromthestormwasduetoapplicationdeficiencies(i.e.,excessivespacingof fasteners),

thesidingobservedwasratedonlyfor90mphbasicwindspeeds(at3-secondgusts)yetitwasinstalledin

anareawithoutcode-specificbasicwindspeedsof 110to120mph.FindingsreportedintheHurricane

CharleyMAT(FEMA488)Reportalsoshowthatvinylsidingfrequentlytearsaroundthefasteners

duringhigh-windevents.Somegeneralrecommendationstoimprovetheperformanceof vinylsiding

withincoastalareasinclude:

n

Drivenailsstraightandleveltopreventdistortionandbucklinginthepanel.

n

Donotcaulkthepanelswheretheymeetthereceiverof insidecorners,outsidecorners,orJ-trim.

Donotcaulktheoverlapjoints.
FEDERAL EMERGENCY MANAGEMENT AGENCY 9-9

EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES 9

n Do

notface-nailorstaplethroughsiding.

n

Usealuminum,galvanizedsteel,orothercorrosion-resistantnailswheninstallingvinylsiding.Aluminum

trimpiecesrequirealuminumorstainlesssteelfasteners.

n

Nailheadsshouldbenolessthan

5

/16of aninchindiameter.Shankshouldbe

1

/8inchindiameter.

(Source:FEMA499)

WoodSiding.ManyrequirementsforwoodsidingmaterialsarecitedinChapter23of theIBC,but

thedetaileddesignandfasteningof woodsidingneedstobecalculatedaccordingtotheC&Cloads

describedinASCE7.TheIRCgivesC&CloadsinTableR301.2(2)thatareapplicabletodesigning

andselectingwood-sidingsystemsforwindspeedsupto110mph.SectionR603.7providesprescriptive

guidelinesforareasinwhichthebasicwindspeedislessthan110mph.Tomeetthedesignrequirements

whenthewindspeedexceeds110mph(forthesecodesections),adesignermustdeterminewindloads

pertheIBCorotherpublicationsreferencedinChapter3of thisguide.Figure9-9showsanexampleof 

eachlayerof materialappliedtotheexteriorof awood-framedhouseusingwoodsiding.Somegeneral

recommendationstoimprovetheperformanceof woodsidingwithincoastalareasinclude:

n

Usenaturallydecay-resistantwoodsuchasredwood,cedar,orcypress.

n

Back-primewoodsidingbeforeinstallation.

n

Carefullyfollowthemanufacturersdetailinginstructionstopreventexcessivewaterintrusion.

n

Usehigh-qualitystainless-steelnailstopreventsidingdamage(i.e.,staining).

INTERIOR INSULATION

WALLS

VAPOR BARRIER

(IF NEEDED)

SHEATHING

HOUSEWRAP

MOISTURE

BARRIER EXTERIOR

SIDING

Wood Siding Example

Figure 9-9.

Example of wood siding on 

a wood-framed house.

BrickVeneer.ThecurrentmasonrycodereferencedintheIBCandIRCisACI530-08/ASCE5-

08/TMS402-08,2008BuildingCodeRequirementsforMasonryStructures.Thiscodeprovides

bothprescriptiveandperformance-basedrequirements.Brick-veneerconstructioninresidential

applicationstendstofollowprescriptiverequirements.BrickveneerisaddressedbytheIRCwith

prescriptiveminimumrequirementsforsizingandspacingof masonryties.Inhigh-windareas(where

morethan30poundspersquarefootof pressureisappliedtothebrick),eachtieisnotpermitted

tosupportmorethan2squarefeetof wallarea.TheICC-600providesdesignrequirementsthat

varywithdesignwindspeed.Atgreaterspeeds,tiesarerequiredtobedesignatedasapercentage
9-10 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

9 EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES

of thetributaryareathatwouldbeusedatlowerwindspeeds.Figures9-10and9-11illustratehow

brickveneersfailedduringHurricaneKatrina,duetoimproperdesignandconstructionof the

wallcovering.

AppendixEof FEMAHurricaneKatrinaRecoveryAdvisory(Attachmentof BrickVeneerinHigh-Wind

Regions)providesrecommendedpracticesforbrick-veneerattachment.Thisadvisorywasbasedupon

observationsfromhurricanesIvanandKatrina.

Top of Wall

Top of

Footer

End 

of Wall

Figure 9-10.

This figure illustrates the layout of brick ties at house under construction in Ocean

Springs, Mississippi, observed after 

Hurricane Katrina. At this wall, nine 

ties were installed (blue circles); 

however, 42 ties (“+” symbol) are 

needed to comply with the advisory.

(Source: FEMA 549)

Figure 9-11.

WAVELAND, MISSISSIPPI: 

House with collapsed brick veneer 

as a result of insufficient wall ties.

(Source: FEMA 549)
FEDERAL EMERGENCY MANAGEMENT AGENCY 9-11

EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES 9

ExteriorInsulationandFinishSystem(EIFS).Thisexteriorwallcoveringsystemhasbeenassessed

indetailinFEMAMATreportsandtheofficialshouldconsultFEMA488,489,and549forinformation

relatedtotheperformanceof thesesystemsfollowingstormevents.Inaddition,theofficialshouldconsult

themanufacturersproductinformationbeforemakingafinaldeterminationonthesuitabilityof the

systemfortherequestedapplication.

9.4 Exterior Floor Coverings

Residentialbuildingslocatedneartheoceanarealmostalwayselevated.Insuchastructure,thespace

underneaththebuildingisexposedtotheelementsunlessithasbeenenclosedwithsheathingoranother

weather-resistantcovering.Applyingsheathingtotheundersideof thebottom-floorjoistsortrusseshelps

minimizecorrosionof framingconnectorsandfastenersbylimitingexposuretosaltsprayandother

environmentalfactors.Thesheathingalsoprotectsinsulationinstalledbetweenthejoists/trussesfromthe

effectsof wavespray.(If fiberglassinsulationisinstalled,thepaperorfoilfaceshouldbeinstalledadjacent

totheundersideof thefloordecking.Barringthis,theinsulationshouldbefacedcorrectlyif amoisture

trapisused,sothatdownwardwater-vapormigrationisnotimpeded.Forlong-termdurability,exteriorgrade

sheathingisrecommendedfortheexposedsheathinganditshouldbefastenedwithstainless-steel

orhot-dippedgalvanizednailsorscrews.)

Suctionforcesinducedbyhighwindswillcausefloorsystemstobepulleddownward.Installingrated

roof sheathingatunder-floorapplicationsandsecuringittothefloorframingusingthesamenailing

scheduleasthatrequiredforroof sheathingwilladequatelysecuretheunder-floorsheathing.Toprevent

moisturefrombeingtrapped,thefloor-joistcavitycreatedbytheunder-floorsheathingshouldbevented.

Figure9-12showshowtheexteriorfloorcovering(whichwasdamagedduringtheeventitself)prevented

decayof thefloorsystemandmayhavecontributedtothesurvivalof thebuilding.

Figure 9-12.

Example of an exterior floor covering system damaged by 

Hurricane Ivan. Note the good 

condition of the floor joists and 

flooring, due to their protection 

from salt spray prior to the storm.

(Source: FEMA 489)
9-12 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

9 EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES

9.5 Soffits

Vinyl(alongwithaluminum)isalsoacommonlyusedmaterialforsoffitsinresidentialbuildings.However,

aluminumandvinylsoffitsareverypronetofailurewhenexposedtohighwinds.If thesoffitsof ahome

fail,wind-drivenraincanentertheceilingandareasabovethetopof thewallandcauseextensivewater

damage.Also,lossof soffitscanincreaseinternalpressuresandleadtolossof theroof sheathingand,

ultimately,tobuildingfailure.

Toperformadequately,thesebuildingelementsmustbeabletoresistsuction(i.e.,downward)pressure

andpositive(upward)pressure.Thegeneralrequirements(thatincludewindloads)containedinSection

1609.1of theIBCandinSectionR301.1of theIRCmandatethatallportionsof buildings(thisincludes

soffits)resistdesign-windpressures.However,neithertheIRCnortheIBCincludeprescriptivedesigns

forsoffitsandverylittleindustryguidanceorinformationaboutbestpracticesexists.IntheIRC,mostof 

theattentiongiventosoffitsfocusesonfireresistance.SectionR703.11.1requiresthatvinylsiding,soffit

andaccessoriesshallbeinstalledinaccordancewiththemanufacturersinstallationinstructions.

Recentassessmentsof high-windeventsmostnotablyFEMA488(inFlorida)andFEMA549(inthe

Gulf Coast)reportwidespreadfailuresinbuildingsoffits.Thelackof prescriptivedesignsforvinyl

soffitshaslikelycontributedtothesewidespreadfailures.TheMATreportsrecommendthatresearchbe

performedsothatprescriptiverequirementsmaybedevelopedandproposedforadoptionintheI-codes.

9.6 Concrete and Masonry Walls

Concreteandmasonrywallsarevaluedincoastalconstructionfor

theirabilitytoresisthighwindloadsandwindbornedebriswhen

properlygroutedandreinforced.However,withrespecttodrainage,

thematerialpropertiesof bothconcreteandmasonryallowthemto

absorbwaterintotheirmassforevaporationlater.Whenexposedto

long,sustainedperiodsof rain,thewater-storagecapacitiesof concrete

andmasonryassembliesmaybeoverwhelmed,forcingexcesswaterto

theinteriorof thebuilding.Thus,themoisture-collectingproperties

of thesewallsystemsmaynotyieldpositiveresults.Whileboththe

IBC(Section1403.2)andIRC(SectionR703.1)allowconcreteand

masonrywallstobeinstalledwithoutwater-resistivebarriers,itis

recommendedthataproperlyinstalledexteriorcladdingsystem

withawater-resistivebarrierbeinstalledtoprovideexcellentoverall

protectionwithincoastalareas.

Siding,panels(e.g.,texturedplywood),andstuccoovermasonryandconcretetypicallyperformwellduring

highwinds.Thekeytothesuccessfulperformanceof asidingandpanelsystemisproperattachment,

involvingasufficientnumberof propercorrosion-resistantfasteners(basedupondesignloadsandtested

resistance)thatarecorrectlylocated.Thedislodgingof stuccoapplieddirectlytoconcretewallshas

occurredinareaswherewiremeshwasnotappliedoverconcrete.

NOTE

Durability: To avoid corrosion 

problems, stainless steel or 

hot-dipped galvanized fasteners 

(preferably heavy-duty, hotdipped galvanized fasteners) 

are recommended for buildings 

located within 3,000 feet of an 

ocean shoreline. If air can freely 

circulate in a cavity (i.e., above a 

soffit), access panels should be 

provided so components within 

the cavity can be periodically 

observed for corrosion. In areas 

with severe termite problems, if 

the use of wood is specified, it 

should be pressure-treated.
FEDERAL EMERGENCY MANAGEMENT AGENCY 9-13

EXTERIOR CLADDING COMPONENTS AND BEST PRACTICES 9

Whererequiredbycode,concreteandmasonrywalls(andveneers)needtobedesignedfortheseismic

load.Whentheuseof aheavycovering(suchasstucco,cement-fiberpanelsorsiding,orbrickveneer)is

specified,theseismicdesignshouldaccountfortheaddedweightof thematerial,anditsconnectionto

thebasematerial(inthecaseof veneer).Inadequateconnectionof veneermaterialtothebasesubstrate

hasbeenaproblemduringpastearthquakesandcanresultinalife-safetyhazard.Somenon-ductile

coverings(e.g.,stuccoandcement-fiberproducts)maybecomecrackedduringseismicevents.If the

useof thesecoveringsisspecifiedinareaspronetolargeground-motionaccelerations,thestructural

sheathingbehindthecoveringshouldbedesignedwithadditionalstiffnesstominimizedamagetothe

wallcovering.

Fiber-cementsidingisaproductusedinapplicationssimilartowoodsidingmaterials.Followingflood

events,itwasnotedtobeaneffectiveexteriorsidingwithinthoseareasexposedtosustainedfloodwaters.

Carefulconsiderationshouldbegiventotheinstallationproceduresrequiredfortheseproductsand

themanufacturersrecommendationsshouldbeconsultedforproperapplication.Anecdotalevidence

followingHurricaneKatrinanotedthatforwood-framedbuildingsitwasimportantthatthesidingbe

attachedtothebuildingatthestudlocationsandthatthisdistanceshouldnotexceed24inches.Thesiding

shouldnothavefastenerswithin1inchof thetopof thesiding.Themanufacturershouldbeconsultedon

whetherconcealedfastenersareappropriatebaseduponthebuildingsrequireddesignwindspeed.

Forbuildingsinareaspronetowildfires,thegreatestprotection

isofferedbyconcrete,masonry,stucco,orcement-fiberpanels

orsiding.Sheathingtheundersideof joistsortrusseswithafireresistant

material(suchascement-fiberpanels)isrecommended.

Cement-fiberpanelsshouldbeattachedwithstainlesssteelorhotdipped

galvanizedscrews.If awallsurfaceisspecified,afire-resistive

systemshouldalsobespecifiedforsoffits(e.g.,stuccoorcement-fiber).

Gableandsoffitventsshouldhaveopeningscoveredwithwiremesh

thatitself hasopeningsnogreaterthan1/4inch,inordertoinhibit

theentryof burningbrands.Foraddedprotection,non-combustible

hingedshuttersthatcanquicklybeplacedintheclosedposition

couldbedesignedandinstalled.

NOTE

Additional guidance on 

seismic-resistant residential 

construction can be found 

in FEMA 232, Homebuilders’ 

Guide to Earthquake Resistant 

Design and Construction. This 

guide provides supplemental 

information on the 2003 IRC 

and also includes “above-code 

recommendations” and low-cost 

measures to improve 

building performance.

FEDERAL EMERGENCY MANAGEMENT AGENCY 10-1

WINDOWS, DOORS, AND OPENING PROTECTION 10

Windows, Doors, and 

Opening Protection

10.1 Introduction

Windows,

skylights,vents,andglazedportionsof doorsarecriticalcomponentsof abuildings

envelope.Codesandstandardsusethetermglazingtoaddressallwindowsandopenings

containingglass.Specifically,ASCE7-05(whichisincorporatedbyreferenceintoboththe

IBCandIRC)providesthefollowingdefinitionforglazing:

GLAZING:Glassortransparentortranslucentplasticsheetusedinwindows,doors,

skylights,orcurtainwalls.

Glazingsystemssimultaneouslyallownaturallighttoenterthebuildingsinteriorandprovideascenic

viewof thecoast.However,thesesystemsareveryvulnerabletodamagefromwindforcesandwindborne

debrisunlessspecificallydesignedtoresistsuchforcesandimpacts.RecentMATinvestigationsand

laboratorytestshaveshownwindowsanddoorsarealsosusceptibletowind-drivenrainpenetration.

Specialconsiderationshouldbegiventothesefeaturesof thebuildingenvelope.Inallareaswhere

buildingsareconstructed,windowsanddoorstendtobemorevulnerabletodamagethanotherportions

of abuildingsenvelope.Incoastalareaswherehighwinds,windbornedebris,andwind-drivenrainare

commonandoftenintensetheirvulnerabilitiesaremorepronounced.

Thischapterpresentsactionsneededtoensurethatwindowsanddoorscanresistthehazardscommon

tocoastalareas.Thischapterdescribestypicalfailuresinwindowsanddoors,discussesrequirements

containedinnationalcodesandstandards,outlinesthenuancesof window-anddoor-testingand

certification,anddiscussessomebest-practicesapproachestoinstallingandprotectingwindowsand

doors.Thechapterfinisheswithadiscussionof garagedoors.

10.2 Window and Door Failure 

Incoastalenvironments,numerouspost-disasterinvestigationsconductedbyFEMAhaveshownthat

windowsandglazedportionsof doorsarevulnerabletoimpactfromwindbornedebris.Thisimpact

forceistheprincipalfailuremodeforthesesystems.Debrisfromthenaturalenvironment(e.g.,treelimbs)

andfromthebuiltenvironment(e.g.,roofingmaterial,sidingmaterial,sawnlumber,etc.)canbecome

windbornedebrisandbreakwindowanddoorglazing.Oncebroken,windowsandglazedportionsof 

doorscanallowwind,windbornedebris,andrainintotheinteriorof thebuilding.Thiscanresultin

thefollowing:

n

Largeamountsof watermayenterabuildinganddamageitscontentsandfinishes.Thereisalsothe

possibilitythatthewatercouldcompromisecertainstructuralmembers.If waterintrusionoccurs,

actionwillnotonlybeneededtoeliminatethewater-induceddamagesonappurtenances(suchas

carpets,cabinets,andfloors),butalsotomitigateallpotentiallong-termmoistureproblemsassociated

withcertainconstructionmaterials.
10-2 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

10 WINDOWS, DOORS, AND OPENING PROTECTION

n

Windforcesorpressuresinsideabuildingaredramaticallyincreasedwhenthebuildingsenvelopeis

breached.Itisnotuncommontoobservesignificantdamagetostructuralandnonstructuralbuilding

elementsfromthisinternalpressurization.Suchdamagemayremainisolatedtoasmallareaorroom

oritmayresultindamagesevereenoughtoinitiatethecompletestructuralfailureof thebuilding.

Waterleakagearoundwindowsanddoorsisalsoquitecommonbutbecausetheeffectsof leakageare

oftensubtle,thefulleffectsof leakageareoftennotreadilyapparent.Leakagefrompoorflashingor

weatherstripping,fromimproperinstallation,orfromdoorsorwindowsbeinginadequatetoresistlocal

conditionscanallowwatertoenterabuildingsinteriorevenwhenthestructureof thewindowor

doorremainsintact.Waterintrusioncancauserotandfastenercorrosionthatweakenthewindowor

doorframeorthewallframingitself.Leakagecanalsocausedamagetointeriorfinishesandfacilitate

moldgrowth.

Wind-pressurefailureof glazingisalsooccasionallyobserved.Windowsanddoorscanfailif theyarenot

strongenoughtoresistwindpressuresfromahigh-windeventorif forcesexertedonthedoorsorwindows

exceedthestrengthof theiranchorage.Figure10-1showshowthefailureof alargewindowledtothe

lossof theroof structure.Whenstrengthisinadequate,thewindowordoorsglazingorframesfail;when

anchorageisinadequate,theentiredoororwindowunitcanbetornfromitsmounting.Negativepressure

(i.e.,suction)failuresaremorecommonbutpositivepressurefailurescanoccuraswell.Figure10-2shows

awindowseparatedfromitsframeduetopositivepressuresactinginwardonawindowsystem.

Newandolderbuildingsmayhavewindowsbrokenbydebrisif windowsarenotprotected.Figure10-3

showsawindowonahomeunderconstructionthatwasbrokenbywindbornedebris,whileFigure10-4

showsanoceanfronthomethatexperiencedwindowbreakagewhenunprotectedglazingwasimpacted

bywindbornedebris.Properlyaddressingthesefailuresrequiresdoorsandwindowstobe:1)correctly

designedandanchoredtoresistwindpressures,2)adequatelyprotectedtoresistwindbornedebris,3)

sufficientlyflashedandweather-strippedtolimitwaterinfiltration,and4)appropriatelyselectedtoresist

localconditions.

Figure 10-1.

PUNTA GORDA, FLORIDA: 

Failure of a roof structure from 

pressurization of a house when the 

window failed on the windward face. 

(Source: FEMA 488)
FEDERAL EMERGENCY MANAGEMENT AGENCY 10-3

WINDOWS, DOORS, AND OPENING PROTECTION 10

Figure 10-4.

Glazing failure due to windborne 

debris. An oceanfront home 

damaged during Hurricane 

Ivan due to windows being 

broken by windborne debris. 

(Source: FEMA 489)

Figure 10-3.

PUNTA GORDA, FLORIDA: 

Glazing failure due to windborne 

debris from displaced roofing. 

(Source: FEMA 488)

Figure 10-2.

PUERTO RICO, 1998: 

Failure due to inadequate pressure 

rating of window. The window 

frame remained attached to the wall 

but the glazed portion was blown 

inward by positive pressures. 

(Source: FEMA 55)
10-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

10 WINDOWS, DOORS, AND OPENING PROTECTION

10.3 Windborne Debris Protection Systems

Damagetoglazingsystemscanbeprevented,oratleastminimized,by

usingglazingoropeningprotectionsystemsthathavebeendesigned

toresistwindandwindbornedebrisforcesspecifiedinthebuilding

code.Impact-resistant(i.e.,debris-resistant)systemsprovideprotection

throughtheuseof laminatedglassorpolycarbonateglazingsystems.

Theuseof physical-openingprotectionsystemssuchasshutters,

screens,orstructuralwoodpanels(asallowedbytheIBCandIRCin

certainhazardareas)isalsoacommonmeansof achievingprotection

forglazing.

Byfar,themosteffectivesolutionisimpact-resistantglazingsystems.

Thesesystemsprovidein-situprotectionandrequirenohuman

actionorinvolvementafterinstallation;theprotectionsystemisinplaceatalltimesanddoesnotneedto

beinstalledpriortostormevents.Further,thesesystemsdonotneedtobeclosed,lowered,orinstalled

likestormpanelsorshuttersystems.Whileimpact-resistantglazingsystemsareoneof themoreexpensive

optionsfordebrisprotection,theirusemaybedeterminedtobeappropriateforhigh-endhomes(where

therelativecostof laminatedsystemsascomparedtothetotalbuildingcostcanbelow)andforbuildings

usedforvacationhomes(whicharenotcontinuouslyoccupied).Theirapplicationmayalsobeappropriate

ontheupperlevelsof homesorbuildings,wheretheinstallationof shuttersmayprovedifficult.

Shutters,screens,andpanelsystemsarethenext-most-desirableoptionafterimpact-resistantsystems.

Thesesystemsprotectvulnerableglazingfromwindbornedebrisbutonlywheninstalledinplacebefore

theeventstrikes.Somestylesof shutters(e.g.,roll-uporaccordion-style)aremadetobedeployedor

positionedtoprotectglazingwithlittleeffort;manyhaveelectric-poweredmotorsthatfacilitatetheir

operation.Of course,electricallyoperatedshuttersneedpowertorunandoccasionallypowerislostearly

duringastorm.Otherstyles,oftencalledstormpanels,aredesignedtobeeasilyremovedandkeptin

storageandinstalledonlywhenastormisapproaching.If inplaceduringahigh-windevent,properly

testedandcertifiedshutters,screens,andstormpanelsareaseffectiveaslaminated,in-situsystems.

However,installingthesepanelsrequiresmoreeffortandplanningbyhomeandpropertyowners.

Woodstructuralpanels(whichincludeplywoodandOSB)areallowedbytheIBCandIRCincertain

applications.Oftenthesepanelsarelarge,singlepanelsthatareunwieldyanddifficulttoinstall

particularlywhenwindsbegintobuildandthepanelsneedtobeinstalledinordertoprotectupper-floor

windows,glazing,orskylights.Itisalsodifficulttopreventahomeownerfromusingwoodstructural

panelsif thesecustomwoodpanelsmeetthedeflectionrequirementsforwhichtheyareused.Wood

structuralpanels,however,arerelativelyinexpensiveandmaybethemostappropriatemethodforlowcost

housing.

10.3.1 Impact-resistant Glazing Systems

Laminatedglazingsystemstypicallyconsistof assembliesfabricatedwithtwo(ormore)panesof glass

andaninterlayerof apolyvinylbutyral(orequivalent)filmlaminatedintoaglazingassembly.Laminated

systemsarenon-porousandhaveslightlydifferentpass/failcriteriainASTME1996.Duringimpact

testing,theglasspanesinthesystemcanfracturebuttheinterlayermustremainintacttopreventwater

NOTE

It is very important to note that 

shutters, screens, and other 

panel systems that protect 

glazing from debris impacts are 

rarely, if ever, rated to reduce 

wind pressures on the windows 

they protect. A system that 

typically has been rated for a 

pressure rating has been rated 

to resist that pressure in order 

to avoid blow-off or excessive 

deflection—not to decrease 

pressure on a window or door 

that the system protects.
FEDERAL EMERGENCY MANAGEMENT AGENCY 10-5

WINDOWS, DOORS, AND OPENING PROTECTION 10

andwindfromenteringthebuilding.Dependinguponthelevelof protection(i.e.,enhancedorbasic),

tearsareallowedinthefilmusedinwindowsbuttearsmustbelessthan

1

/16inchwideandlessthan5

incheslongandcannotallowa3-inch-diameterballtopassthroughthetear.Afterimpacttesting,the

laminatedglazingsystemsmustresistthecyclicpressuretestsof ASTME1886.

Polycarbonateglazingsystemsarealsousedinplaceof traditionallaminatedglazingsystems.Polycarbonate

systemstypicallyconsistof plasticresinswhicharemoldedintosheetswhichprovidelightweight,clear

glazingpanelswithhighimpact-resistancequalities.Thestrengthof thepolycarbonatesheetsismuch

higherthannon-laminatedglass(i.e.,morethan200timesstronger)oracrylicsheetsorpanels(morethan

30timesstronger).Severalbrandsof polycarbonatesusedasglazing(suchasLexanandMakrolon)

arecommonlyavailable.Bothimpact-resistantwindowsandshuttersystemsmaybeconstructedusing

polycarbonates.

10.3.2 Shutter, Screen, and Panel Systems

Shutters,screens,andnon-woodpanelsystemsareseparatesystemsandaretestedindependentlyfrom

theglazedportionsof thewindowsanddoortheyprotect.Whilecertifiedshuttersprotectglazingfrom

debrisimpactforanidentifiedmissileataprescribedimpactspeed,mostshuttersystemsareporousand

donotsignificantlyreducewindpressuresontheglazingitself.Glazingprotectedbyshuttersdoesnot

needtobedebris-impact-resistantbutitdoesneedtobestrongenoughtoresistdesignwindpressures.

Duringtesting,theshuttersystemmustwithstandtheimpactof thetestmissilewhilepreventingthe

missilefrompenetratingtheinnermostplaneof thetestspecimen.Also,aftersuccessfultesting,there

canbenoopeningsformedthatallowa3-inch-diameterballtopassthroughthem.

Tobeeffective,shuttersshouldfullycovertheglazingtheyaremeanttoprotect.Inretrofitinstallations,

shuttersareoccasionallyobservedthatdonotcovertheentirewindoworareobstructedbywindowunit

airconditionersorotherappliances(seeFigure10-5).

Also,asabest-practicesapproach,shuttersshouldbeanchoredtothewallsurroundingthewindow,and

nottothewindowordoorframeitself.Shuttersshouldneverbeanchoredtothewindowframeunless:1)

thewindowisproperlyanchoredtothewallinafashionthatresistsimposedwindpressures,and2)the

shutteriscertifiedtoperformproperlywhenattachedtothewindowordoorframe.Typicalinstallation

of shutters,screens,andpanelsrequiresbracketsorothermountingdevices(suchasanchors)tobe

securedtothewallsorotherelementsthatsurroundthewindowandnotthewindowordooritself.

Shuttersinstalledonupperfloorsorindifficult-to-reachareascanbechallengingtoinstalloroperate.

Severalmotorizedstylesareavailabletofacilitatetheoperationanddeploymentof shuttersindifficult-toreach

areas.If motorizedshuttersareused,theshuttersystemshouldalsobemanuallyoperable.If not,

lossof electricalpowercanrendertheshuttersineffectivepriortoaneventandmightpreventopening

afteranevent.
10-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

10 WINDOWS, DOORS, AND OPENING PROTECTION

10.3.3 Wood Structural Panels

Woodstructuralpanelsarenotrequiredtobetestedandcertified,butareassumedtoofferanacceptable

levelof protectionif installedasprescribed.TheIBCandIRCspecifyminimumpanel-thickness

requirementsalongwithmaximumspansforthewoodstructuralpanels.Limitingpanelspansplaces

upperlimitsonthestresseswithinthepanelandcontrolsdeflectionof thepanel.Likeshutters,wood

structuralpanelsareconsideredporousandarenotcertifiedtoreducewindpressuresontheglazing

itself.Windowsanddoorsprotectedbywoodstructuralpanelsmuststillmeetwind-pressurerequirements

specifiedinthecode.

10.4 Protection Requirements for Windborne Debris

Whilethepotentiallydevastatingeffectsof windbornedebrishavebeenknownforyears,windborne

debrisprovisionshaveonlyrecentlybeenintroducedintonationalcodesandstandards.The1995edition

of ASCE7firstspecifiedthedebris-impactprotectionrequirementsforglazingfromwindbornedebris.

Thatstandardstatedthatglazinginthelower60feetof allbuildingslocatedinregionswherethebasic

3-secondgustwindspeedequaledorexceeded110mphhadtobeprotectedagainstwindbornedebris

orthatbuildingshadtobedesignedtoresisthigherinternalpressures.Thestandardallowedbuildings

inthesehigh-windareastohaveunprotectedglazingbutrequiredthatthestructurebedesignedto

resisthigherwindpressures(frominternalpressurization).Thisapproach,whilevalidfromastructural

standpoint,allowedbuildingcontentsandfurnishingstobedamagedbywaterentryfrombroken

glazing.Further,thisapproachleftthebuildingenvelopeunprotectedagainstknownhazards.Lossof 

windowsduetowindbornedebrismayresultindamagethatismanytimesthereplacementcostof the

building.Thisisduetowhatisoftenextensivedamagetobuildingcontentsandthelossof operationsof 

thedamagedbuilding.Thesecostswerecomparabletoafull-buildingloss,althoughthestructurehad

notfailed.

Since1995,theperformancerequirementsforwindbornedebrisprotectionhaveincreasedwhilethe

locationswherewindbornedebrisprovisionsarerequiredhavebeenlessenedslightly.Currently,theIBC

andIRCnolongerallowdesignerstohavetheoptionof designingbuildingsforhigherinternalpressures

withunprotectedglazinginwindbornedebrisregions;theglazingmustbeprotected.Thisensuresthat

newbuildingsnotonlycanresistwindpressuresbutalsocanprovideprotectionagainstwindborne

debrisandminimizeimpacttohomesandbusinesses,therebyreducinginsuranceclaimscausedbywater

enteringbrokenglazing

TheIRC,IBC,andASCE7-05currentlydefinewindbornedebrisregionsasfollows:

WindborneDebrisRegion:Portionsof hurricane-proneregionsthatarewithin1mileof the

coastalmeanhigh-waterlinewherethebasicwindspeedis110mph(49m/s)orgreater;orportionsof the

hurricane-proneregionwherethebasicwindspeedisequaltoorgreaterthan120mph(54m/s);orHawaii.

andwherehurricane-proneregionsaredefinedas:

Hurricane-proneRegions: Areasvulnerabletohurricanes,definedas:

1.TheU.S.AtlanticOceanandGulf of Mexicocoastswherethebasicwindspeedis90mph(40m/s),and

2. Hawaii,PuertoRico,Guam,VirginIslands,andAmericanSamoa.
FEDERAL EMERGENCY MANAGEMENT AGENCY 10-7

WINDOWS, DOORS, AND OPENING PROTECTION 10

Asdefined,windbornedebrisregionsinthecontinentalUnitedStates

extendalongtheGulf of MexicofromTexastothesoutherntip

of Florida,andalongtheAtlanticCoastfromthesoutherntipof 

FloridatoMassachusetts.ThisalsoincludesHawaii,U.S.territories

andprotectorates,andmostof coastalAlaska.

Thewindbornedebrisregionsdescribedinthe2006IBCandIRC

arelessextensivethanwhatwasspecifiedinANSI/ASCE7-95.

Inthe1995standard,allhurricane-proneareaswithabasicwind

speedof 110mphorgreaterwereconsideredtobewindbornedebris

regions.Nowonlyhurricane-proneareaswithabasicwindspeedof 

110mphthatarewithin1mileof thecoastareconsideredtobein

thewindbornedebrisregion(exceptinHawaii,whereallportionsof 

allislandsexist,bydefinition,withinthewindbornedebrisregion).

TherequirementsforresidentialconstructionarelistedinIRCSection

R301.2.1.2.Thissectionrequiresthatglazedopeningsinbuildings

locatedinwindbornedebrisregionsbeprotectedfromwindborne

debrisandthatsuchprotectionmustmeettherequirementsof the

LargeMissileTestof anapprovedimpact-resistingstandard,orASTME1996andASTME1886(using

MissilesCorD).Section1609.1.2of theIBChasrequirementsthattakeintoconsiderationtheuseof the

buildingandlocationof theglazing.Glazedopeningswithin30feetof grademustresisttheLargeMissile

Testof ASTME1996(usingMissileDorE)andglazedopeningsmorethan30feetabovegrademust

meettheSmallMissileTestof ASTME1996.Itisimportanttounderstandthatwhenglazingprotection

isrequired,itisrequiredforallglazingonabuilding.Itisanincorrectassumptionthattheprotection

onlyneedstobeinstalledtoprotectopeningsonthesideof thebuildingthatreceivespositive(or

predominant)windpressures.Further,theapprovedsystemsneedtobeinspectedforcompliance.Figure

10-5illustrateshowapanelshutterwasinstalledincorrectlyaroundwindow-mountedairconditioning

units,leavingmuchof thewindowunprotected.

NOTE

Delineating windborne debris 

regions is not an exact science 

and would benefit from 

further research. While postevent assessments indicate 

that 3-second gust winds as 

low as 80 mph can dislodge 

aggregate surfaced roofing 

with sufficient momentum to 

damage glazing, recent research 

suggests that in wooded areas, 

the 2006 windborne debris 

regions may be conservative. 

According to the best practices 

recommended in recent FEMA 

MAT reports from the 2004 

and 2005 hurricane seasons, 

windborne debris protection is 

suggested for all Exposure C 

areas where wind speeds are 

110 mph or greater.

Figure 10-5.

PENSACOLA, FLORIDA:

Shutters had been attached to this 

building in order to protect it from 

windborne debris. However, areas 

above and below the air conditioning 

units were left unprotected. 

(Source: FEMA 489)
10-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

10 WINDOWS, DOORS, AND OPENING PROTECTION

ASTME1886,StandardTestMethodforPerformanceof ExteriorWindows,

CurtainWalls,Doors,andImpactProtectiveSystemsImpactedbyMissile(s)and

ExposedtoCyclicPressureDifferentialsisaconsensus-basedtestingprotocol

forcertifyingglazingsystems.However,certificationtoASTME1886

inandof itself isnotadequatetodetermineadequacyof aglazing

systemforagivenarea.

ASTME1886isnotastandalonedocumentandrequiresinputfrom

aspecifyingauthorityortheAHJsuchasacity,county,orstate

codeenforcementofficewhichdeterminesactualtestingconditions

andregulatescompliancewithsuchtestsandconditions.Thetest

methodstandardizesthesizeandweightof asmallmissile,thesize

andrangeof weightsforlargemissilesatvariousspeeds,andsetsforththemethodstotestassembliesfor

missileimpactsandsubsequentcyclicpressuretests(althoughitremainstheresponsibilityof thespecifying

authoritytoprovidetheactualtestingcriteria).Thesecriteriainclude:numberof testspecimens,basic

windspeed,missileimpactspeed,numberandlocationof impactsrequiredduringcertification,andthe

numberof cyclesanddurationof thecyclicloadtesting.

ASTME1996augmentsASTME1886byspecifyingtheweightof thelargemissiletobeusedintesting

perASTME1886andtheimpactvelocitiesforthelargeandsmallmissiles.TheASTMstandards

identifymorestringentrequirementsforbuildingsinhigherbasicwindspeedzonesandforcritical

facilities.Table10-1presentstwoASTME1996largemissilerequirementsfordifferentwindzonesand

buildingclassifications.

TheASTMstandarddefinesbasicprotectionlevelsforglazingforallbuildings,andforbuildingsrequiring

enhancedprotection.Section6.2.1of ASTME1996describesfacilitiesandtheirrequiredprotection

level.ThewindzoneslistedinASTME1996are:

WindZone1 Ð Areaswherethebasicwindspeedisgreaterthanor

equalto110mphandlessthan120mph,andHawaii.

WindZone2 Ð Areasmorethan1milefromthecoastlinewherethe

basicwindspeedisgreaterthanorequalto120mphandlessthan130.

Thecoastlineisdelineatedbythemeanhigh-watermark.

WindZone3 Ð Areaswherethebasicwindspeedisgreaterthanor

equalto130mphandareaswithin1mileof thecoastline,wherethebasic

windspeedisgreaterthanorequalto120mph.

Thismaybeconfusingtodesigners,builders,andlocalofficials,becauseitappearsthatthesearedifferent

criteriathanwhatispresentedintheIBCandIRC.However,thisisnotthecase.TheASTMstandard

windzoneshelpdefinethemissilesizeandspeedtobeusedfordebrisimpact-resistancetestingandare

neededtocarryoutthetestsrequiredbythecodes.Localofficialsneedtocloselyreviewthecertification

of testedglazingsystemstodetermineif theyareappropriateforthatjurisdiction,buildinglocation,and

buildinguse.Particularattentionshouldbegivento:

NOTE

The Engineering Wood 

Association (formally the 

American Plywood Association) 

has prepared five brochures 

that present hurricane-resistant 

shutter design for wood-frame 

and masonry buildings. The 

brochures are available online 

at the Engineering Wood 

Association Web site at

http://www.apawood.org.
FEDERAL EMERGENCY MANAGEMENT AGENCY 10-9

WINDOWS, DOORS, AND OPENING PROTECTION 10

n

Basic(design)windspeed.(ItshouldmatchtheASCE7-05basicwindspeedmaporthemaps

containedintheIRCorIBC.)

n

Designwindpressures.(PressuresshouldbebaseduponC&CloadsperASCE7-05,theIBC,

orIRC.)

n

Sizeof theappropriatemissile(whichdependsuponbuildinguse,buildingheight,andwindspeed).

Table 10-1.

(Source: ASTM E1996)

Missile Level Missile Impact Speed

(m/s)

A 2 g + 5% Steel Ball 39.62 (130 f/s)

B 910 g + 100 g (2.0 lb. + 0.25 lb.) 2x4 in. 15.25 (50 f/s)

52.5 cm + 100mm (1 ft. - 9 in. + 4 in.) Lumber

C 2050 g + 100 g (4.5 lb. + 0.25 lb.) 2x4 in. 12.19 (40 f/s)

1.2 m + 100mm (4 ft. + 4 in.) Lumber

D 4100 g + 100 g (9.0 lb. + 0.25 lb.) 2x4 in. 15.25 (50 f/s)

2.4 m + 100mm (8 ft. + 4 in.) Lumber

E 4100 g + 100 g (9.0 lb. + 0.25 lb.) 2x4 in. 24.38 (80 f/s)

2.4 m + 100mm (8 ft. + 4 in.) Lumber

TABLE 2 - Applicable Missiles

TABLE 3 - Description Levels

NOTE 1 – For Missiles B, C, D and E also use Missile A for porous shutter assemblies (see 8.4)

Levels of

Protection

Enhanced Protection

(Essential Facilities) Basic Protection

Assembly Height < (30 ft) > (30 ft) < (30 ft) > (30 ft) < (30 ft) > (30 ft)

9.1 m 9.1 m 9.1 m 9.1 m 9.1 m 9.1 m

Wind Zone 1 D D C A None None

Wind Zone 2 D D C A None None

Wind Zone 3 E D D A None None

Unprotected
10-10 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

10 WINDOWS, DOORS, AND OPENING PROTECTION

Itisalsoimportanttonotethatwindpressuresspecifiedonproductapprovalorcertificationsheetsfor

shutters,screens,andpanelsystemsarethepressuresatwhichthesystemwastestedforresistancetoblowoff.

Thesesystemshavenotbeentestedtoreducethepressuresonthewindowsandglazingtheyprotect

and,therefore,thewindoworglazingsystembehindtheopeningprotectivedevicemuststillbedesigned

toresistthedesignwindpressure;theprotectivedeviceonlypreventsdebrisimpacttotheglazing.

BoththeIRCandIBCcontainexceptionsthatpermit

7

/16-inchthick(minimum)woodstructuralpanels

tobeforusedforwindbornedebrisprotection.Itisimportanttonotethatthesepanelsshouldnothave

amaximumdimensionof morethanof 8feetandtheymustbeproperlyfastenedtothebuildingto

resistwindforcesappropriateforthatlocation.Inaddition,whenwoodstructuralpanelsareusedfor

windbornedebrisprotection,theIRCandIBCbothrequirethatthepanelsbe:1)precut,2)attached

totheframingsurroundingtheglazedopenings,3)securedwithattachmenthardwareprovided,and4)

theattachmentsshallbedesignedtoresisttheC&CloadsdeterminedinaccordancewithIBCSection

1609(i.e.ASCE7-05).TableR301.2.1.2of theIRCandTable1609.1.2of theIBCcontainprescriptive

attachmentschedules(i.e.,details)suitableforbuildingswithmeanroof heightsupto33feetforbasic

windspeedsupto130mph.Figure10-6showsaglazeddoorthatwasnotprotectedwithanytypeof 

systemandwassubsequentlydamagedbywindbornedebris.

Figure 10-6.

PENSACOLA, FLORIDA:

Failure of glazing from windborne 

debris created by dislodged tile roofing. 

(Source: FEMA 489) 

TheIBCcontainsotherexceptions,whichallowgreenhouseswithnopublicaccessandglazinginthe

upperfloorsof tallerbuildingstobeconstructedwithoutwindbornedebrisprotection.Exceptionsto

glazingprotectionintallerbuildingsapplywhen:1)theglazingisatleast60feetabovetheground,and2)

theglazingislocatedaminimumof 30feetaboveanyaggregatesurfacedroofswithin1,500feetof the

buildingglazinginquestion.(Theseexceptionsareconsistentwiththerequirementsof ASTME1996.)

Prescriptivestandardsgenerallyassumethatabuildingsenvelope(e.g.,walls,wallcoverings,windows,

roof decking,roof coverings,etc.)willremainintactandthebuildingwillnotbedamagedbytheimpact

fromwindbornedebris.Theassumptionisthataholeintheexteriorof thebuildingmaybecreated,butit

willnotexposetheinsideof thefacilitytowindsthatwouldresultinhighinternalpressuresactingonthe

structuralsystem.ICC-600requiresglazinginwindbornedebrisregionstobeprotectedtomeetthelarge
FEDERAL EMERGENCY MANAGEMENT AGENCY 10-11

WINDOWS, DOORS, AND OPENING PROTECTION 10

missilecriteriaof ASTME1886andASTME1996topreventdamage.ASCE7-05alsostatesinSection

1.4that,Buildingsandotherstructuresshallbedesignedtosustainlocaldamagewiththestructural

systemasawholeremainingstableandnotbeingdamagedtoanextentdisproportionatetotheoriginal

localdamage.However,itisveryimportanttonotethatwalls,roof decks,andothernon-glazedbuilding

componentsarenotrequiredtobeimpact-resistantsystemsbytheIRC,IBC,orASCE7-05.Onlysome

statecodes(suchastheFloridaBuildingCode)containimpact-resistancerequirementsfornon-glazed

buildingcomponents.TheserequirementsarelimitedtohazardareasdefinedasHighVelocityHurricane

Zones(HVHZ)andonlyforcriticalandessentialfacilitiesoperatingwithintheHVHZs.FEMA361and

theICC-500,whichprovidedesigncriteriaforsaferoomsandstormshelters,respectively,requireallroof,

wall,glazing,doors,andopeningsonthesaferoomorsheltertobedebris-impactresistant.

10.5 Window and Door Leakage

Hurricanesandcoastalstormscanposesignificantproblemsfromwater-infiltrationduetowind-driven

rain.Leakagecanoccurbetweenthedoororwindowandtheirframesandbetweenthedoor/window

framesandthewallsontowhichtheyaremounted.Coastalstormssuchastropicalstormsandhurricanes

generatewindsthatmayapproachorexceedthewindspeedsobservedduringdesignwindevents.Assuch,

thesewindsgeneratehigh-windpressuresontheoutsidesof thebuildings,exploitinganyvulnerability

arounddoorsandwindowsandallowingwatertoenterbuildings.Further,leakageratestypicallyincrease

withgreaterwindspeeds.Whiletheamountof waterentrythatcanresultfromleakagearoundwindows

anddoorswilltypicallybemuchlessthantheamountof waterentrythatcanresultfromabreachinthe

buildingenvelope,actionscanandshouldbetakentohelpreduceleakagearounddoorsandwindows.

Theseactionsareoftencode-plusorbest-practicesapproaches.

10.5.1 Code Requirements for Window and Door Leakage

Properdoorandwindowconstructioniscriticaltoreducingwaterinfiltration.SectionR613.4of the

IRCandSection1714.5.1of theIBCrequirewindowsandslidingdoorstobecertifiedperAAMA/

WDMA/CSA101/I.S.2/A440,Standard/SpecificationforWindows,Doors,andUnitSkylights.Hingedoors

mustbecertifiedperASTME330,StandardTestMethodforStructuralPerformanceof ExteriorWindows,Doors,

Skylights,andCurtainWallsbyUniformStaticAirPressureDifference.Bothstandardsspecifywind-pressure

andwater-leakagecriteriathatmustbemetinordertocomplywithcoderequirements.

Ingeneral,water-leakagetestsareconductedatmuchlowerdifferentialpressures(typically20percent)

thanthepressuresusedtodeterminethestrengthof theglazing,window,ordoorassembly.Thisimplies

thatsomewaterentrythroughdoorsandwindowsshouldbeanticipatedduringaneventthatproduces

designwindpressuresandwind-drivenrain.

10.5.2 Reducing Window and Door Leakage

FEMA499,TechnicalFactSheetNo.22:WindowandDoorInstallation,WindowandDoorInstallation,

providessomebest-practicesapproachesthatcanbetakentoreducewaterinfiltration.Panflashing(i.e.,

flashingunderwindowsills),weatherstripping,andthresholdsealsarediscussed.Otheractionscanbe

takentoreducethepotentialforwaterentry.Theseinclude:

Vestibules.Designingavestibuletoprotectadoorentryisonemethodof managingwaterinfiltration

problems.Throughthisapproach,boththeinnerandouterdoorscanbeequippedwithweather

stripping,andthevestibuleitself canbedesignedtotoleratewater.Forexample,water-resistantfinishes
10-12 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

10 WINDOWS, DOORS, AND OPENING PROTECTION

(e.g.,concreteortile)canbespecified,andthefloorcanbeequippedwithadrain.Asaresult,asecondary

layerof protectionisprovidedfortheprimaryentrance(viathevestibuleandvestibuledoor).

Doorswing.Out-swingingdoorsofferanadvantagecomparedtoin-swingingdoorassemblies.With

out-swingingdoorassemblies,theweatherstrippingislocatedontheinteriorsideof thedoor,whereitis

lesssusceptibletodegradationthantheexposedweatherstrippingonin-swingingdoorassemblies.Also,

someinterlockingweather-strippingproductsareavailableforout-swingingdoorassembliesthatprovide

betterperformancethanthoseusedonin-swingingdoorassemblies.

Finishselection.Onedesignapproachtodealwithleakageistoavoidrunningcarpet(orotherfinishes

thatcanbedamagedbywater)entirelytotheedgeof wallsthatcontainalargeamountof glazing.

Instead,astripof water-resistantmaterial(suchastile)couldbespecifiedalongthewallsoif lightto

moderateleakageoccurs,thepotentialfordamagetointeriorfinishesandcontentsisgreatlyreduced.

10.6 Window and Door Assembly Capacities 

Windowanddoorassembliesmustbestrongenoughtowithstandwindpressuresactingonthemandbe

fastenedsecurelyenoughtotransferthosewindpressurestotheadjacentwall.Pressurefailuresof doors

orwindowscanallowglazingtofractureorglazingframesorsupportstofail.Anchoragefailurescan

allowentiredoororwindowunitstoberippedfromtheirwalls,asshowninFigure10-7.Eithertypeof 

failureresultsinthefailureof thebuildingenvelopeandallowswindandwaterintothebuilding.

10.6.1 Code Requirements for Strength and Anchorage

BoththeIRCandIBCcontainspecificrequirementsforthewindresistanceof windowsanddoors.

SectionR613.3of theIRCrequiresthatexteriorwindowsanddoorsbedesignedtoresistthewind

pressuresspecifiedinTableR301.2(2).TableR301.2(2)listspositiveandnegativewindpressuresforC&C

forvariouslocationswithinthebuilding.Areasnearroof andwalledgesandareasnearcorners,where

turbulencecreateslocalizedhighwindpressures,mustbedesignedforhigherloads.TableR301.2(2)

Figure 10-7.

PUNTA GORDA ISLES, FLORIDA: 

Anchorage failure in sliding 

glass door failure. 

(Source: FEMA 488)
FEDERAL EMERGENCY MANAGEMENT AGENCY 10-13

WINDOWS, DOORS, AND OPENING PROTECTION 10

isbaseduponExposureBconditionsforbuildingswithameanroof heightof 30feetorless.Table

R301.2(2)pressuresmustbemultipliedbyfactorslistedinTableR301.2(3)fordifferentmeanroof heights

andexposures.

TheIBCrequirementsaresimilarbutarelessprescriptiveandmoreperformance-based.WhiletheIRC

hastabulatedwindpressures,Chapter16of theIBCspecifiesacceptablemethodsof calculatingwind

loadsand(inSection1603.1.4)requiresthatconstructiondocumentslistwindpressuresforC&C.

IBCSection1405.12,ExteriorWindowsandDoors,requireswindowsanddoorstobetestedinaccordance

withIBCSection1714.5,whichliststwomethodsof establishingwindresistance.Section1714.5.1allows

doorsandwindowstobelabeledperAAMA/WMDA/CSA101/I.S.2/A440;Section1714.5.2allows

doorsandwindowstobetestedperASTME330.Thelatteroptionhasadditionalrequirementsregarding

glasssupportsandframingthatareoutlinedinSection2403andpressureratingsforSection1714.5.2are

outlinedinChapter16,thestructuraldesignchapterof theIBC.

AAMA/WMDA/CSA101/I.S.2/A440listsdesigntestpressuresof 15,25,30,and40psf.Windows

anddoorsusedinareaswherewindpressuresaregreaterthan40psf needtobetestedperASTME330.

Forresidentialconstruction,localofficialsmustensurethatproductsproposedareadequatetoresistthe

C&Cloadsof TableR301.2(2).Forengineeredconstruction,thedesignershouldspecifywindpressures

requiredforwindowsanddoorsandshouldbasethemonC&CloadsfromeitherChapter6of ASCE

7-05orChapter16of theIBC.

SectionR613.8.1of theIRCrequiresthatwindowsandglassdoorsbeanchoredinaccordancewith

publishedmanufacturersrecommendations.Themanufacturersinstallationinstructionsshouldmatch

thoseusedwhentheunitsweretestedandcertified.Substituteanchoragesystemsareallowedif they

provideequalorgreateranchoringperformanceasdemonstratedbyacceptedengineeringpractice.

IRCcontainsFiguresR613.8(1)throughR613.8(8)thatprovideminimumanchoragedetails.Thedetails

requirewindowsanddoorstobeanchoredinafashionthatadequatelytransfersloadsfromthewindows

anddoorstotheadjacentwalls(thewallsarecalledsubstratesinthatcode).Whenthespacebetween

thewindowordoorframeandthewallsroughopeningis11

/2inchesorless,shimsorbuckscanbe

installedandfastenerscanextendfromthedoororwindowframetothewall.Whenthespaceisgreater

than11

/2inches,thebucksneedtobesecurelyfastenedtothewallandthedoor,orwindowframesneed

tobesecurelyfastenedtothebucks.Thisrequirementlimitstheshearlengthof fastenersto11

/2inches

andreducesthepotentialforbendingfailuresinthefasteners.

TheIBCrequirementsaresimilarbutdonotprovidetheprescriptivedetailscontainedintheIRC.IBC

Section1405.12.1requireswindowsanddoorstobeinstalledinaccordancewithapprovedmanufacturers

instructions.TheIBCrequiresfastenersizeandspacingbeprovidedintheinstructionsandthatthe

fastenersizeandspacingbebaseduponthemaximumloadsusedincertificationorcompliancetests.

Foradequateperformance,themanufacturersinstallationinstructionsmustbefollowed.Localauthorities

shouldrequirethattheinstallationinstructionsbepresentonsite.Further,installationsshouldbeinspected

toensurethatcompliancehasbeenachievedwiththoseinstructions.
10-14 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

10 WINDOWS, DOORS, AND OPENING PROTECTION

Tominimizeissuesrelatedtocorrosion,theuseof fiberglassorvinylframesarerecommendedfor

buildingslocatedwithin3,000feetof anoceanshoreline.Theuseof stainlesssteelframeanchors,

fasteners,andhardwareisalsorecommendedwithintheseareas.Inareaswhereseveretermiteorinsect

infestationproblemsexist,woodframesshouldeitherbetreatedorshouldbeconstructedwithwoodthat

isnaturallyinsect-androt-resistant.Shimsandbucksshouldbepressure-treated.Sincesomepressure

treatmentincreasesthemoisturecontentof framing,theuseof materialthatiskilndriedaftertreatment

issuggestedtocontrolshrinkage.

Inareaswhereinsectinfestationproblemsexist,metaldoorassembliesarerecommended.If concrete,

masonry,ormetalwallconstructionisusedtoeliminatetermiteproblems,woodusedforblockingor

bucksshouldbetreatedornaturallyinsect-androt-resistantspeciesof woodshouldbeused.

10.7 Garage Doors 

Post-eventhurricaneandtornadoassessmentsincludenumerousexamplesof failuresof garage(or

vehicle-access)doors.Garagedoorshaveexperienced:

n

Outward-actingSuctionFailures.Doorshavebuckledandpulledoutward,asshownin

Figure10-8.

n

Inward-actingPositivePressureFailures.Doorshavebuckledorpushedinward,asshownin

Figure10-9.

n

HardwareFailures.Failuresinthehardwarethatlaterallysupportsgaragedoorsandallowsthem

toopenandclose.

Failuresof garagedoorscanallowsignificantamountsof waterandwindtoenterabuilding.Because

itiscommonforgaragestobeconstructed(atleastinpart)withwater-resistantmaterials,waterentryis

oftenlessof aconcernthantheinternalpressureincreasethatgarage-doorfailurescreate.Agarage-door

failureisabreachof thebuildingenvelope.Thebreachincreasesinternalpressureswithinthatareaof 

thebuildingandmayleadtobuildingfailure.

Becauseof theirsizeandrelativelylongspans(ascomparedtowindowsandotherdoors),garagedoors

mustresisthigherforcesfromthesamewindpressuresthatactonwindowsandaccessdoors.However,

garagedoorstypicallyhaveroomtodeflectmorethanwindowsandaccessdoorsandtheincreased

deflectioncanbeusedtoresistloads(providedthatthetracksdonotfail).

SectionR613.5of theIRCrequiresgaragedoorstobetestedinaccordancewithASTME330,Standard

TestMethodforStructuralPerformanceof ExteriorWindows,Doors,Skylights,andCurtainWallsbyUniformStatic

AirPressureDifferenceorANSI/DASMA108,StandardMethodforTestingSectionalGarageDoors:Determination

of StructuralPerformanceUnderUniformStaticAirPressureDifferenceandrequiresdoorstomeettheacceptance

criteriaof ANSI/DASMA108.ASTME330establishesthemethodsusedtoapplyandmeasurewind

pressures;ANSI/DASMA108establishesfailurecriteriarelatedtobuildingfailure.
FEDERAL EMERGENCY MANAGEMENT AGENCY 10-15

WINDOWS, DOORS, AND OPENING PROTECTION 10

Likethetestingof windowsanddoorsperAAMA/WDMA/CSA101/I.S.2/A440,neitherASTME330

norANSI/DASMA108establishestestpressures.Thereforecertificationdatamustbecloselyexamined

todetermineif thelabeledproductisappropriateforthedesignwindpressuresattheproposedlocation.

Also,somemunicipalitiesrequiregaragedoorstobetestedatpressuresinexcessof thedesignwind

pressures.TheC&CwindpressuresinTableR301.2(2)of theIRCprovideminimumdesignpressures

thatthelabeleddoorshouldmeet.

TableR301.2(2)listspositiveandnegativewindpressuresonC&Cforbasicwindspeedsbetween85

mphand170mph.Positivepressuresacttowardthebuildingsurface;negativepressuresactawayfrom

thebuildingsurface.AsdiscussedinSection10.6,thelistedpressuresrelatetoExposureBconditionsfor

buildingswitha30footmeanroof height;thevaluesmustbemultipliedbytheadjustmentfactorslisted

inTableR301.2(3)forotherexposurecategoriesandothermeanroof heights.

Figure 10-9.

Positive pressure failure 

of garage door. 

(Source: FEMA 549)

Figure 10-8.

Negative pressure failure 

of garage door.

(Source: FEMA 488)
10-16 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

10 WINDOWS, DOORS, AND OPENING PROTECTION

TableR301.2(2)alsolistswindpressuresforvariouslocationswithinabuildingthatconstituteeffective

windareas.Thelocationsincludethreeareasspecifiedfortheroof (Zones1,2,and3correspondingto

theinterior,corner,andeaveandgablezones)andtwoareasspecifiedforthewalls(Zones4and5).Zone

4wallpressuresareforlocationsawayfromcorners;Zone5pressuresareforareaswithin4feetof the

corner,wherewindpressuresarehigher.IRCFigureR301.2(7)graphicallyshowsthelocationsof the

C&Cwindzones.

Whilesomemanufacturersprovidewindspeedandexposureratingsfortheirproducts,labelsonmany

garagedoorsdonotincludewindspeedorwindpressureratings.Whilenotrequiredtobeincluded

ontheproductlabeling,ANSI/DASMA108doesrequirethatthepositiveandnegativepressureused

intestingberecordedontheANSI/DASMA108TestReportForm.Thestandardalsorequiresthat

themodelnumber,description,andoperatinghardwarebedocumented.Wherewindspeedorwind

pressuresarenotspecificallyprovidedfortheproduct,buildersandofficialscanrefertotheTestReport

Formtoensurethatthegaragedoorassemblyhasbeentestedtoresistthedesignwindpressureslisted

inTableR301.2(2).Inwindbornedebrisregions,theIRCSectionR301.1,2alsorequiresthatglazingin

garagedoorsbeprotectedfromwindbornedebris.

10.8 Additional Resources

AmericanSocietyforTestingandMaterials:

n

ASTME1886,Performanceof ExteriorWindows,CurtainWalls,Doors,andStormShuttersImpactedbyMissile(s)

andExposedtoCyclicPressureDifferentials

n

ASTME1996,StandardSpecificationforPerformanceof ExteriorWindows,CurtainWalls,DoorsandImpact

ProtectiveSystemsImpactedbyWindborneDebrisinHurricane;

n

ASTME2112,StandardPracticeforInstallationof ExteriorWindows,DoorsandSkylights

n

ASTME330,StructuralPerformanceof ExteriorWindows,Doors,SkylightsandCurtainWallsbyUniformStatic

AirPressureDifference.(www.astm.org)

AmericanNationalStandardsInstitute:

n

ANSI/DASMA108,StandardMethodforTestingSectionalGarageDoors:Determinationof StructuralPerformance

UnderUniformStaticAirPressureDifference
APPENDIX A
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A APPENDIX
FEDERAL EMERGENCY MANAGEMENT AGENCY A-3

APPENDIX A
A-4 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

A APPENDIX
FEDERAL EMERGENCY MANAGEMENT AGENCY A-5

APPENDIX A
A-6 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

A APPENDIX
FEDERAL EMERGENCY MANAGEMENT AGENCY A-7

APPENDIX A

SAMPLE

NOTE

The V-zone certificate is not a 

substitute for and can not be 

used without the NFIP Elevation 

Certificate (see Fact Sheet No. 

4), which is required for flood 

insurance rating.
A-8 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

A APPENDIX

Checklist for Permit Review

General

Structuralsystemsresistanttoflotation,collapse,orpermanentlateralloading

DFEconsistentwiththesiteslocationontheapplicableFIRM

MechanicalandelectricalsystemselevatedtoatorabovetheDFE

Waterandsewerdesignedtoallowminimuminfiltrationfromfloodwaters,orpreventitentirely

MaterialsbelowtheDFEareresistanttoprolongedwaterexposure

AllareasbelowtheDFEaredesignedforauseconsistentwithNFIPregulations

Sitedrainagethatwillreduceexposuretoflooding

Foundationdesignedtoresisterosionandscour

Submittedappropriategeotechnical(soils)information

Floorframingperpendiculartowaveaction

Corrosion-resistantexteriorconnections

Propersplicesforlonggirders

Verificationof thewindexposureclassification

Keyconnectionsinplacetoallowacontinuousloadpath

Upliftresistantconnectiontotransferloadsfrommainfloortofoundation

Upperwallstransferloadstolowerwalls,bypassingfloors

Roof loadstransferredtowalls

Sufficientroof systemandroof framingtoresistuplift

Shearwallsproperlyspecifiedmaterialsandfastenedproperly

Openingsintheshearwallsdesignedsoastonotcompromisetheirstrength
FEDERAL EMERGENCY MANAGEMENT AGENCY A-9

APPENDIX A

Appropriateroofingsystemspecifiedgivenwindspeedrequirements

IfCMUconstructionisspecified,itisappropriatelyreinforcedandroofelementsproperly

connected

Flashingroof/windowsufficientforwind-drivenrain.

Seismic

Connectionsufficienttoresistapplicablelateralloads

Roofingsystemseismic-resistantandincludedinloadingcalculations

A-Zone

Crawlspaceequippedwithfloodopenings1inch2per1squarefootof area

Stemwallsproperlybackfilledandcompacted

Foundationwallsaresolidfoundationwalls

Pierfoundationsufficientlydesignedforoverturning,duetowind,flood,erosion,scour,and

seismicloads

Pilefoundationadequatelydetailed,including:size,installationmethod,embedmentdepth,bracing

andproperconnectiontothestructure.(Isitresistanttoverticalandhorizontalloading?Areany

diagonalpilesrequired?)

Fillisproperlystabilized,sloped,andcompacted

Breakawaywallsutilizedreflectdesignsufficienttoresist10psf of force,butnottoexceed20psf

Anyrampsandstairwaysdesignedtoresistflood-relatedloadsand(intheeventdesignfloodconditions

aremet)willbreakawaywithoutcausingdamagetothemainstructure

Anygaragesevaluatedagainstrequirementsof ASCE24Section9.3

Anychimneysorfireplacesevaluatedagainstrequirementsof ASCE24Section9.4

Anyswimmingpoolsevaluatedagainsttherequirementsof ASCE24Section9.5
A-10 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

A APPENDIX

V-Zone

Pierfoundationsufficientlydesignedforoverturning,duetowind,flood,erosion,scour,and

seismicloads

Pilefoundationadequatelydetailed,including:size,installationmethod,embedmentdepth,bracing,

andproperconnectiontothestructure.Pilefoundationevaluatedforresistancetoverticaland

horizontalloading.(Areanydiagonalpilesrequired?)

Breakawaywallsutilizedreflectdesignsufficienttoresist10psf of force,butnottoexceed20psf

Areanyrampsandstairwaysdesignedtoresistflood-relatedloadsand(intheeventdesignflood

conditionsaremet)willbreakawaywithoutcausingdamagetothemainstructure

Garagesmeetrequirementsof ASCE24Section9.3

Chimneysandfireplacesmeetrequirementsof ASCE24Section9.4

Swimmingpoolsmeetrequirementsof ASCE24Section9.5

Roofing

Plansexplainproposedinstallationtechniquesandcoverwhethermaterialsarecorrosion-resistant,

andwhetheranydissimilarmetalsareincontactwitheachother

Reviewof substitutionstothemanufacturersspecificationsabouttheroof system

ExteriorCladding

Connectionssuitableforhazardsandresistanttowaterintrusion

DoorsandWindows

Doorsandwindowsmeetwindloadrequirements,includinganyappropriatemissile-impact

requirements

Allconnectionsandmaterialscorrosion-resistant

Locationsconsistentwithshearwallrequirements.(Substitutionsforlargeropeningscannotbemade

withoutconsentof theengineer)

Utilities

AllutilitiesproperlyelevatedtoatorabovetheDFE

Allutilitiesproperlyattachedandanchoredtotheirsupports
FEDERAL EMERGENCY MANAGEMENT AGENCY A-11

APPENDIX A
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A APPENDIX
FEDERAL EMERGENCY MANAGEMENT AGENCY A-13

APPENDIX A
A-14 LOCAL OFFICIALS GUIDE FOR COASTAL CONSTRUCTION

A APPENDIX