Lateral Bracing in Gable End Walls

    Scope Images
    Image
    Right – Horizontal bracing is added to strengthen the gable end wall
    Scope

    Install lateral bracing in gable end walls to ensure the building will resist design wind pressures. This guide provides an overview of lateral bracing in gable end walls with a focus on applications in hurricane-prone regions or other high-wind areas.

    • If the house is in a hurricane-prone region or other high-wind area, strengthen the gable end wall connection to the wall below, in accord with the requirements of the IBHS Fortified Home Hurricane and High-Wind Standards.
    • Install 7/16 in.-structural sheathing (OSB or plywood) on the vertical face of the gable end wall.
    • Brace gable end walls taller than 48. inches in height to resist wind forces by installing a framing assembly at each gable wall stud. The framing assembly incudes horizontal braces, vertical retrofit studs, and compression blocks.

    See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and EPA Indoor airPLUS.

     

    Description

    Gable end walls are the triangular sections of wall that extend above the top plate at the gable ends of houses with gable roofs. Gable end walls that are inadequately braced or improperly anchored are vulnerable to collapse during high winds.

    During a hurricane, tornado, or high winds, gable end walls can be damaged or detached from the rest of the structure, leading to severe damage to the roof and other structural members of the house (Figures 1 and 2). A compromised gable end wall can allow rainwater to enter the building causing severe damage, including saturation of insulation and ceiling drywall, potentially leading to collapsed ceilings and extensive damage to the interior of the home and its contents.

    This gable end wall failed because connectors were missing at the points of support (blue circles) and the outlookers were not connected to the end truss (yellow circle).
    Figure 1. This gable end wall failed because connectors were missing at the points of support (blue circles) and the outlookers were not connected to the end truss (yellow circle). (Source: FEMA P-2077 2020.)

     

    Roof structure failure due to inadequate bracing. (Source: FEMA, Building Performance: Hurricane Andrew in Florida.
    Figure 2. Roof structure failure due to inadequate bracing. (Source: FEMA, Building Performance: Hurricane Andrew in Florida.)

     

    Wind forces both push (inward acting) and pull (outward acting) on houses, so it is critical to brace the gable ends to resist wind pressures in both directions. The potential critical failure points are the gable end wall connections at the roof framing and sheathing above and the wall below, gable wall framing members, and gable wall sheathing.  

    The International Residential Code (IRC 2018) requires exterior building components and their attachments to be capable of resisting design wind pressures. For some high-wind regions, the IRC requires wind design in accordance with other methods including the International Building Code (IBC 2018).  

    Homes located in coastal high-wind areas including Hurricane-Prone Regions generally require enhanced attachment that can withstand greater wind speeds than the rest of the country. The IRC defines Hurricane-Prone Regions as areas along the Atlantic and Gulf Coasts where wind velocity is >115 mph, and Hawaii, Puerto Rico, Guam, the Virgin Islands, and American Samoa (see the IRC wind map in the Climate tab). Confirm with the local building department if the house is in a hurricane-prone region and if local requirements exceed those of the IRC.

    The IRC does not specify requirements for bracing gable end walls for wood framing but has minimum requirements for continuous roof sheathing at gable end walls, including fastener (nail) type, spacing, and penetration depth into structural members (see the Compliance tab for details). Section R603.3.1.1 of the 2018 IRC specifies gable end walls with heights greater than 10 feet (3,048 mm) are to be anchored to foundations or floors in accordance with IRC Table R603.3.1(1) or R602.3.3.1.1(2). IRC Section R603.3.2.1 specifies stud size and thickness for the gable end walls.

    Table of gable endwall to floor connection requirements.
    Table 1. Gable endwall to floor connection requirements. (Source: 2018 IRC)

     

    The Insurance Institute for Business and Home Safety® (IBHS) offers guidance, best practices, and voluntary construction standards and programs for building in disaster-prone areas including hurricane and high-wind zones. The IBHS FORTIFIED HOME™ standard is designed to make homes more resilient and durable; guidance is available for New Construction and Existing Homes in Hurricane zones and High-Wind zones  There are three levels of FORTIFIED Home: FORTIFIED Roof™ focuses on the roof; FORTIFIED Silver focuses on roof overhangs, opening protection, gable ends, and attached structures; FORTIFIED Gold focuses on tying all of the components of the structure together. 

    The IBHS FORTIFIED Home Hurricane Standard requires gable walls subjected to high winds to have structural sheathing attached to the vertical face consisting of 7/16-in. OSB or plywood. The IBHS FORTIFIED Home High Wind Standard requires gable end walls to have a structural wall sheathing that is a minimum of 3/8-inch plywood or OSB or equivalent.

    How to Install Lateral Bracing in Gable End Walls

    1. Strengthen the gable end wall, as required:
      • Minimum 3/8-inch thick structural wall sheathing over the entire gable end wall
      • Maximum 24-inch spacing between studs on gable end walls.
    2. Strengthen the gable end wall connection to the wall below using metal bracket connectors and one of the following methods:
    • Attach the bottom chord of the gable end wall to the wall below using right angle gusset brackets consisting of 14-gauge or thicker material with a minimum load capacity of 350 pounds. Install the right-angle gusset brackets along the wall where the gable end wall height is greater than 3 feet at the spacing specified in the table below. Use a minimum of two fasteners specified by the manufacturer to attach the angle gusset bracket.
    • For a conventionally framed gable end wall, attach each stud along the wall where the height of the wall is greater than 3 feet to the bottom plate using a stud-to-plate connector. Connect the bottom plate to the wall below using 4.5-inch, ¼-inch-diameter screws.

     

    Table 2. Spacing of Right Angle Gusset Brackets Connecting Gable End Wall to Wall Below. (Source: FORTIFIED Home High Wind Standard).

    Exposure Category

    Wind Speed, mph
    Maximum 3-Sec. Gust

    Maximum Spacing of Right Angle Gusset Brackets
    C 110 38 in.
    C 120 32 in.
    C 130 28 in.
    C 140 24 in.
    C 150 20 in.
    B 110 48 in.
    B 120 40 in.
    B 130 36 in.
    B 140 30 in.
    B 150 26 in.

    For steps 3 through 5, refer to Figure 3.

    3. Install horizontal bracing, perpendicular to the gable wall, at the bottom chord or ceiling joist, and at the top chord or roof rafter, at each gable end wall stud greater than 3 feet high. Attach bracing using three #8 x 3-in. screws at each truss chord or rafter and joist.

    4. Attach a vertical retrofit stud, between the upper and lower horizontal bracing, to each existing gable wall stud. 

    • Attach a retrofit stud to the upper and lower horizontal bracing using metal straps, minimum 20-gauge x 1-1/4-in. wide with pre-punched fastener holes, using #8 screws.
    • Attach retrofit stud to existing stud using #8 x 3-in. screws at 6 inches on-center
    • The maximum allowable gap between the retrofit stud and bracing is 1/8-in. at the lower brace and 1/2-in. at the upper brace. 

    5. Install compression blocks on horizontal bracing bearing tightly against the vertical retrofit stud, to restrain horizontal movement. Attach compression blocks using three #8 x 3-in. screws; screws must not go through the strapping. 

    Gable End Wall Bracing.
    Figure 3. Gable End Wall Bracing. (Source: FEMA P-804 2010.)

     

    Ensuring Success

    Dimensional lumber used for braces, studs, and blocking should conform to applicable standards or grading rules. Metal plate connectors, straps, and anchors should have product approval and should be approved for connecting wood to wood. Straps and tie plates should be manufactured from galvanized steel with a minimum thickness provided by 20 gauge and have holes sized for 8d nails.

    See if local building codes have specific requirements or ask the local building department. For disaster resistance, comply with the roofing requirements defined by the IBHS Fortified Home Program.

    Climate

    The International Residential Code does not have specific requirements for gable end wall bracing but general requirements for wood wall framing are provided in Section R602.

    Homes located in coastal high-wind areas including Hurricane-Prone Regions generally require enhanced attachment that can withstand greater wind speeds than the rest of the country. The IRC defines Hurricane-Prone Regions as areas along the Atlantic and Gulf Coasts where wind velocity is >115 mph, and Hawaii, Puerto Rico, Guam, the Virgin Islands, and American Samoa.

    Wind Regions of the United States.
    Figure 1. Wind Regions of the United States. (Source: IRC 2018, Figure R301.2(5)A)

     

    The Insurance Institute for Business and Home Safety® (IBHS) offers guidance, best practices, and voluntary construction standards and programs for building in disaster-prone areas including hurricane and other high-wind zones. The IBHS FORTIFIED Roof™ program includes guidance on sealed roof decks, flashing, and shingle attachment. 

     

    Right and Wrong Images
    Image
    Wrong – This house under construction is lacking wall to truss bracing and the bottom chord of the scissor trusses is several feet above the top of the end wall top plate
    Wrong – This house under construction is lacking wall to truss bracing and the bottom chord of the scissor trusses is several feet above the top of the end wall top plate
    Image
    Wrong – The roof sheathing was inadequately fastened and gave way causing the gable end wall to fail
    Wrong – The roof sheathing was inadequately fastened and gave way causing the gable end wall to fail
    Image
    Wrong – The gable end wall failed because the rigid foam sheathing was not backed up by plywood or OSB.
    Wrong – The gable end wall failed because the rigid foam sheathing was not backed up by plywood or OSB.
    Image
    Right – Proper bracing hardware for retrofitting gable ends
    Right – Proper bracing hardware for retrofitting gable ends
    Image
    Right – Horizontal bracing is added to strengthen the gable end wall
    Right – Horizontal bracing is added to strengthen the gable end wall
    Image
    Right - Installation steps for the L-bent strap method of bracing a gable end wall
    Right - Installation steps for the L-bent strap method of bracing a gable end wall
    Image
    Right – An existing gable wall is reinforced with horizontal braces that butt up to the gable end wall and connect back to multiple trusses; retrofit studs make full contact with the wall and the compression blocks and are connected to the horizontal brac
    Right – An existing gable wall is reinforced with horizontal braces that butt up to the gable end wall and connect back to multiple trusses; retrofit studs make full contact with the wall and the compression blocks and are connected to the horizontal brac
    Image
    Right – Hurricane strapping attaches every roof truss to a wall stud.
    Right – Hurricane strapping attaches every roof truss to a wall stud.
    Videos

    Compliance

    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

     

    2018 and 2021 International Residential Code (IRC)

    R802.10.3 Bracing. Trusses shall be braced to prevent rotation and provide lateral stability in accordance with the requirements specified in the construction documents for the building and on the individual truss design drawings. In the absence of specific bracing requirements, trusses shall be braced in accordance with accepted industry practice such as the SBCA Building Component Safety Information (BCSI) Guide to Good Practice for Handling, Installing and Bracing of Metal Plate Connected Wood Trusses.

    Table R802.11 provides rafter or truss uplift connection forces from wind.

    R802.11.1 Uplift resistance. Roof assemblies shall have uplift resistance… shall be designed in accordance with accepted engineering practice.

    Exceptions are included in the 2021 IRC for:

    -Areas where the uplift force per rafter or truss does not exceed 200lbs (90.8kg).

    Areas where the basic wind speed does not exceed 115mph, the wind exposure category is B, the roof pitch is greater than 42-percent slope, the roof span is 32 feet or less, and rafters and trusses are spaced not more than 24 inches on center.

    R803.2.3. Installation. Wood structural panel used as roof sheathing shall … shall not cantilever more than 9 inches (229 mm) beyond the gable end wall unless supported by gable overhang framing.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IRC

    Section R102.7.1 Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)

    Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

     

    IBHS FORTIFIED Home High Wind Standard

    Gable end walls must have structural wall sheathing (minimum of 3/8-in. plywood or OSB or equivalent).

    Gable end walls need to be braced.

    For wood frame roof structures, if framing of the gable is not complete and a professional engineer is NOPT being used to design a bracing solution, a contractor/builder can install continuous 2- x 4-in. lateral bracing at the ceiling from the gable end truss to the opposite end of the attic at 6 ft. o.c. Each lateral brace must have a minimum 20 gauge metal strap connected to the lateral brace that also wraps over the bottom chord of the gable end wall plate/truss, and for wood frame wall construction below, over the top plate of the wall below and that is connected to a stud in the wall below. When the wall below is masonry, the strap must connect to the bond beam at the top … lateral brace with four (4) 10d nails.

    If framing of the gable is not complete and a professional … which can be obtained from a certified FORTIFIED Home Evaluator.

    Section A103.6.1 Screws. Screws shall be a minimum #8 size with head diameters no less than 0.3 in. Screw lengths shall be no less than indicated in the Figures and in Tables. Permissible screws include deck screws, wood screws, or sheet metal screws (without drill bit–type tip, but can be sharp pointed). Screws shall have at least 1 in. of thread. Fine-threaded screws or drywall screws shall not be permitted. Note that many straps will not accommodate screws larger than #8.

    Section A103.6.2 Nails. Unless otherwise indicated in the provisions or drawings, where fastener lengths are indicated in Figures and Tables as 1¼ in., 8d common nails with shank diameter 0.131 in. and head diameters no less than 0.3 in. shall be permitted. Unless otherwise indicated in the provisions or drawings, where fastener lengths are indicated in Figures and Tables as 3 in., 10d common nails with shank diameter of 0.148 in. and head diameters no less than 0.3 in. shall be permitted.

    Section A103.7 Fastener Spacing. Fastener spacing shall be as follows:

    1. distance between fasteners and the edge of lumber shall be a minimum of ½ in. unless otherwise indicated,
    2. distance between fasteners and the end of lumber shall be a minimum of 2½ in.,
    3. distance between fasteners parallel to grain (center-to-center) when straps are not used shall be a minimum of 2½ in. unless a ½-in. stagger (perpendicular to the grain) is applied for adjacent fasteners, then the distance between fasteners parallel to the grain shall be a minimum of 1¼ in.,
    4. distance between fasteners across grain (row spacing) when straps are not used shall be a minimum of 1 in., and the
    5. distance between fasteners inserted in metal plate connectors, straps, and anchors as defined in Section A103.4 (above) shall be those provided by holes manufactured into the straps.

    A104.2 Horizontal Braces. Horizontal braces shall be installed approximately perpendicular to the top and bottom chords of the existing roof trusses or approximately perpendicular to the rafters and ceiling joists at the location of each … shall not exceed 1/8 in.

    A104.6 Connection of gable end wall to wall below. The bottom chords or bottom members of wood framed gable end walls shall be attached to the wall below using … referenced in Sections A104.2, A104.3, A104.4 or A104.5.

    Existing Homes

    The FEMA Wind Retrofit Guide for Residential Buildings (FEMA P- 804) has information for retrofitting existing gable end walls in residential buildings.

    Step 1: Check the stud spacing and wall connections for the existing gable end walls.

    • Conventionally framed gable end walls can be strengthened by using straps or right-angle brackets to anchor each stud longer than 3 feet to the upper and lower framing members (frequently existing studs are only toe-nailed).

    Step 2: Vertical framing members can be strengthened by installing retrofit studs that are adjacent to the gable end wall stud and extend from the top of the lower horizontal brace to the bottom of the upper horizontal brace.

    • The retrofit stud is a nominal 2-inch lumber member used to structurally supplement an existing gable end wall. A maximum gap of 1/8 inch is permitted between the retrofit stud and the bottom horizontal brace and ½ inch is permitted between the top edge of the retrofit stud and the horizontal brace.
    • Fasten each retrofit stud to the top and bottom horizontal brace members with a minimum of a 20-gauge, 1 ¼ inch wide flat metal strap with pre-punched fastener holes. The strap should be fastened using #8 wood screws or 8d nails. They should also be fastened to the side of the vertical gable end wall studs with #8 wood screws or 10d nails spaced at 6 inches o.c.

    Step 3: Follow the steps in the Description Tab to install lateral bracing as required.

    Step 4: Ensure the sheathing thickness is at least 3/8 inch and re-nail sheathing if required.

    More Info.

    Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

    References and Resources*
    Author(s)
    Insurance Institute for Business & Home Safety
    Organization(s)
    IBHS
    Publication Date
    Description
    Guide describing the requirements by FORTIFIED Home™ for improving the home's resistance in severe thunderstorms, straight-line wind events, and high winds at the outer edges of tornadoes.
    Author(s)
    Insurance Institute for Business & Home Safety
    Organization(s)
    IBHS
    Publication Date
    Description
    Guide describing the requirements by FORTIFIED Home™ for improving the home's resistance in severe thunderstorms, straight-line wind events, and high winds at the outer edges of tornadoes.
    Author(s)
    Kapur,
    Mahadevia,
    Park,
    Passman,
    Perotin,
    Reeder,
    Seitz,
    Sheldon,
    Tezak
    Organization(s)
    FEMA
    Publication Date
    Description
    Report providing guidance on how to improve the wind resistance of existing residential buildings in Mississippi and across the Gulf Coast.
    Author(s)
    Florida Division of Emergency Management
    Organization(s)
    Florida Division of Emergency Management
    Publication Date
    Description
    Report describing the hurricane retrofit guide with focus on walls and wooded framed walls.
    Author(s)
    International Code Council
    Organization(s)
    ICC
    Publication Date
    Description
    2018 edition of code for residential buildings that creates minimum regulations for one- and two-family dwellings of three stories or less, bringing together all building, plumbing, mechanical, fuel gas, energy and electrical provisions for one- and two-family residences.
    Author(s)
    International Code Council
    Organization(s)
    International Code Council
    Publication Date
    Description
    2018 edition of code for commercial buildings that brings together all structural, plumbing, mechanical, fuel gas, energy and electrical provisions for all buildings except detached one- and two-family residences and townhouses up to three stories.
    Author(s)
    Kapur,
    Mahadevia,
    Park,
    Passman,
    Perotin,
    Reeder,
    Seitz,
    Sheldon,
    Tezak
    Organization(s)
    FEMA
    Publication Date
    Description
    Report providing guidance on how to improve the wind resistance of existing residential buildings in Mississippi and across the Gulf Coast.
    *For non-dated media, such as websites, the date listed is the date accessed.
    Contributors to this Guide

    The following authors and organizations contributed to the content in this Guide.

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