Roof Escape Openings for Flood-Prone Areas

    Scope Images
    Image
    Commercially available “roof hatch” products provide an openable access to the roof for maintenance and emergency egress that meets code dimensional requirements
    Scope

    In extreme-flood-prone and coastal regions, design and construct openings providing occupants with a safe means of access and escape to the roof:

    • Install an openable dormer window, skylight, or roof hatch that meets minimum code dimension requirements.
      • Minimum egress dimensions are 20 inches wide by 24 inches high, providing a net clear opening of at least 821 square inches (5.7 square feet).
      • Egress openings should not be higher than 44 inches above a floor or landing surface or must have permanent access via a ladder, stair, or ramp.

    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 Indoor airPLUS. 

    Description

    In extreme flood events, evacuation of building occupants may become necessary. Flood waters may rise quickly enough to prevent ground-based evacuation and it may be necessary for occupants to seek temporary shelter in the upper portions of buildings until evacuation can occur. The last place of available refuge is typically a roof. Installing a means of accessing the roof is recommended in high-flood-risk areas.

    Most building codes require egress openings with minimum dimensions of 20 inches wide by 24 inches high providing a net clear opening of at least 821 square inches (5.7 square feet). (See IRC R310 Emergency Escape and Rescue Openings, Sections 2.1, 2.2, 2.3, and R326.) A roof opening meeting this requirement can be provided by a commercially available “roof hatch” (see Figures 1 and 2), an operating skylight, or a dormer with windows of sufficient net open area (see Figure 3). Figure 1 also shows exterior walls that are insulated and constructed as flood-resistant “wash and wear” walls by using water-resistant rigid foam and high-density spray foam that is coated with acrylic latex paint. Figure 3 also shows appropriate insulation, air sealing, and flashing details so that dormers that are constructed on the roof do not become a source of air or water leakage or unnecessary heat loss.

    In high-flood-risk areas, install a roof hatch or openable skylight, min. 20x24 inches or 821 in.2 to serve as a means to access the roof for refuge
    Figure 1. In high-flood-risk areas, install a roof hatch or openable skylight, at least 20x24 inches or 821 square inches to serve as a means to access the roof for refuge (Source: PNNL).
    Commercially available “roof hatch” products provide an openable access to the roof for maintenance and emergency egress that meets code dimensional requirements
    Figure 2. Commercially available “roof hatch” products provide an openable access to the roof for maintenance and emergency egress that meets code dimensional requirements (Source: Building Science Corporation). 
    A dormer with an openable window (not shown) can provide access to the roof if flood waters rise too high and too quickly; the dormer should be properly insulated, flashed, and air sealed
    Figure 3. A dormer with an openable window (not shown) can provide access to the roof if flood waters rise too high and too quickly; the dormer should be properly insulated, flashed, and air sealed (Source: Building Science Corporation). 

     

    Rafters or roof trusses are typically spaced 16 or 24 inches on center. Commercially available roof hatches typically have dimensions of 30 inches by 36 inches. Rafters on each side of the hatch location can be doubled to provide extra strength for the blocking above and below the opening, as shown in Figure 4. Another option would be to install a skylight with a minimum rough frame opening of 22 inches wide by 42 inches long; this would also meet the building code egress requirements. 

    Install extra support and blocking if needed around the opening for a roof hatch or skylight that is wider than the rafter spacing
    Figure 4. Install extra support and blocking if needed around the opening for a roof hatch or skylight that is wider than the rafter spacing (Source: Building Science Corporation). 

     

    For a skylight to be used as an egress opening, the skylight must be openable for its entire area.

    Any egress opening should not be higher than 44 inches above the floor or landing surface or must have permanent access via a ladder, stair, or ramp. See Figure 5. 

    If the egress opening is more than 44 inches above the floor or landing, install permanent access via a ladder, stairs, or ramp.
    Figure 5. In flood-prone areas, a roof egress opening can be installed; if more than 44 inches above the floor or landing, install permanent access via a ladder, stairs, or ramp (Source: PNNL).

    In vented attic assemblies, the shaft connecting the skylight or hatch to the insulated ceiling should be insulated and air sealed as part of the home’s exterior envelope (Figure 6).

    Insulate and air seal the shaft around a skylight in a vented attic.
    Figure 6. Insulate and air seal the shaft around a skylight in a vented attic (Source: Building Science Corporation). 

     

    Homeowner Preparation for Flooding

    The following list provides flood preparation tips for homeowners. For more information see the flooding page from Ready.Gov and Flood Preparedness.

    • Do not try to escape rising floodwater by going into the attic unless you have roof access or unless it’s your only option.
    • Know your risk. Look at the FEMA flood maps.
    • Create an emergency supply kit.
    • Develop an evacuation and family communications plan and share it with your family members.
    • Keep storm drains clear. If your property is prone to flooding, have sandbags, plastic sheeting, and other flood-fighting materials on hand.
    • Learn how to turn off water, gas, and electricity connections to your home in the event that your home is flooded. Contact your local utility companies for guidance.
    • During a flood watch or warning: Listen to the radio, TV, or check the Internet to see whether a flood watch or flood warning for your area. A flood watch means that flooding is possible. A flood warning indicates that flooding is imminent or occurring. Evacuate if told to.
    • Consider flood insurance. Most homeowners’ insurance policies do not cover flood damage. Ask your insurance agent about obtaining flood insurance from the National Flood Insurance Program.
    Ensuring Success

    In extreme flood events, building occupants may need to evacuate. Flood waters may rise quickly enough to prevent ground-based evacuation and it may be necessary for occupants to seek temporary refuge on the roof. A means of accessing the roof is recommended in high-risk flood areas.

    Most building codes require egress openings with minimum dimensions of 20 inches by 24 inches providing a net clear opening of at least 821 square inches (5.7 square feet). A roof opening meeting this requirement can be provided by a roof access product, an operating skylight, or a dormer with windows of sufficient net open area.

    Climate

    See the FEMA flood maps website for an assessment of the risk of flooding in your location. 

    See the FEMA tsunami maps website for an assessment of the risk of tsunamis in your location. 

    Right and Wrong Images
    Image
    This reinforced concrete apartment building with exterior roof access in Minamisanriku, Japan, was designated as a vertical evacuation refuge during tsunamis; 44 people survived the 2011 Tohoku tsunami on the fenced roof
    This reinforced concrete apartment building with exterior roof access in Minamisanriku, Japan, was designated as a vertical evacuation refuge during tsunamis; 44 people survived the 2011 Tohoku tsunami on the fenced roof
    Image
    An exterior metal staircase was added to this concrete building for roof access and refuge during tsunamis in Kesennuma, Japan
    An exterior metal staircase was added to this concrete building for roof access and refuge during tsunamis in Kesennuma, Japan

    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.

    2009201220152018,  and 2021 International Residential Code (IRC)

    R301.2.1 Wind design criteria. Buildings shall be constructed in accordance with the wind provisions of this code using the ultimate design wind speed in Table R301.2(1) as determined from Figure R301.2(5)A. Where not otherwise specified, the wind loads listed in Table R301.2(2) adjusted f height and exposure using Table R301.2(3) shall be used to determine design load performance requirements.

    R310.1 Emergency Escape and Rescue Opening Required. Basements, habitable attics, and every sleeping room shall have not less than one operable emergency escape and rescue opening.

    R310.2.1 Minimum Size. Emergency escape and rescue openings shall have a net clear opening of not less than 5.7 square feet (0.530 m2).

    R310.2.2 Minimum Dimensions. The minimum net clear opening height dimension shall be 24 inches (610 mm). The minimum net clear opening width dimension shall be 20 inches (508 mm). The net clear opening dimensions shall be the result of normal operation of the opening.

    R310.2.3 Maximum Height from Floor. Emergency escape and rescue openings shall have the bottom of the clear opening not greater than 44 inches (1,118 mm) above the floor.

    R326 Habitable Attics. R2326.4 Means of Egress. The means of egress for habitable attics shall comply with the applicable provision of Section R311.

    ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures

    Chapter 6, “Tsunami Loads and Effects” covers design provisions for coastal locations at risk for tsunamis.

    Existing Homes

    Roof access hatches and openable skylights can be installed as a retrofit measure. Existing dormers could be considered for egress if window openings are or could be enlarged to provide adequate space for exiting.

    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)
    Institute for Business & Home Safety
    Organization(s)
    Institute for Business & Home Safety
    Publication Date
    Description
    Report covering reducing risk from flooding.
    Author(s)
    Coulbourne,
    Jones,
    Durham,
    Kapur,
    Koumoudis,
    Line,
    Low,
    Overcash,
    Passman,
    Reeder,
    Seitz,
    Smith,
    Tezak
    Organization(s)
    FEMA
    Publication Date
    Description
    Volume 1 of a two-volume report providing a comprehensive approach to planning, siting, and risk management for homes constructed in coastal environments.
    Author(s)
    Coulbourne,
    Jones,
    Durham,
    Kapur,
    Koumoudis,
    Line,
    Low,
    Overcash,
    Passman,
    Reeder,
    Seitz,
    Smith,
    Tezak
    Organization(s)
    FEMA
    Publication Date
    Description
    Volume II of a two-volume report providing a comprehensive approach to desing, construction, and renovation of homes located in coastal environments.
    *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.

    Building Science Corporation

    Pacific Northwest National Laboratory

    Last Updated

    Mobile Field Kit

    The Building America Field Kit allows you to save items to your profile for review or use on-site.

    Sign Up  or  Log In

    Did you find this information helpful?