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Roof Construction for Fire Resistance

Description

Homes in the wildland-urban interface are at risk for wildfires. However, there are several steps that builders and homeowners can take to increase a home's resistance to wildfires, starting with the home’s roof (see Figure 1).

This house survived a wildfire due in part to fire-resistant walls and roof while surrounding houses were destroyed
Figure 1. This house survived a wildfire due in part to fire-resistant walls and roof while surrounding houses were destroyed (Photo from Decra Roofing Systems, Used With Permission). 

 

Builders and homeowners can choose Class A-rated roofing materials. Roof coverings come with a Class A, B, or C rating. Class A products are the most fire resistant. Class A roof coverings include the following roofing types:

  • Clay tile
  • Concrete tile
  • Slate
  • Metal roofing
  • Class A rated fiberglass asphalt shingles

When designing the home, architects and designers can design the roofs to be more resistant by using a simpler roof design that has fewer valleys, dormers, and roof-wall junctures where dry leaves and pine needles can collect and create a fire hazard.

Other steps designers and builders can take include the following:

  • Attic vents: Use ember and flame-resistant vents. Screen all attic vents with wire mesh or hardware cloth with openings no larger than 1/8 inch. Don’t use fiberglass or plastic mesh that could melt or burn. Install soffit vents on fascia or nearer to the edge not the house. Consider an unvented attic design.
  • Chimney: Cover with a non-flammable screen with openings between 3/8 inch and ½ inch to prevent embers from escaping.
  • Eaves and Soffits: Box in eaves or install flat (horizontal) soffit coverings that are noncombustible like fiber cement or ignition-resistant like fire retardant-treated wood. Cover roof edges with metal drip edge that extends into the gutters to cover the edge of the flammable roof decking and keep out embers.
  • Gutters: Cover gutters with gutter screens to prevent the accumulation of leaves and pine needles.

More information about designing and constructing fire-resistant roofs can found in the following Building America Solution Center guides:

Asphalt Shingle Roofs

Clay or Concrete Tile Roofs

Metal Roofs

Vented vs Unvented Attic

Roof Vents

Gutters and Downspouts

More Info

References and Resources*

Coastal Construction Manual - Principles and Practices of Planning, Siting, Designing, Constructing, and Maintaining Residential Buildings in Coastal Areas, Fourth Edition, Volume II, FEMA P-55

Publication Date
·
Author(s)
Coulbourne William,
et al.
·
Organization(s)
Federal Emergency Management Agency,
FEMA,
Applied Technology Council,
ATC,
URS Group,
DK Low and Associates,
Atkins,
TLSmith Consulting
Description
Volume II of a two-volume report providing a comprehensive approach to design, 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.

Pacific Northwest National Laboratory

Last Updated

Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.