Q: Can asphalt shingles be used on homes in areas that are prone to wildfires?
A: Steve Quarles, advisor emeritus at the University of California Cooperative Extension, responds: You should not be worried about putting asphalt shingles on a roof located in a wildfire-prone area if those shingles have a Class A fire rating. Asphalt shingles can have different compositions, and when installed properly, fiberglass composition shingle roof coverings comply with the provisions required for a Class A roof covering.
The Class A rating is specified in the ASTM Standard Test Method E-108, which evaluates the fire rating of a roof covering and has three parts. The first part evaluates flame spread over the roofing material. The second part evaluates the ability of a roof covering to resist flames on top of the covering from burning through it and other components (such as sheathing and underlayment) in the roof assembly and entering into what would be your attic or ceiling space. The final part of the test evaluates the roof covering’s ability to resist generating embers, also known as firebrands, that can become airborne and spread a fire. With asphalt shingles, there are combustible components (namely the asphalt), but the noncombustible components (fiberglass and granules) provide the performance sufficient to comply with the provisions of the test.
It is important to point out that this test specifically evaluates the roofing material and does not evaluate the vulnerability of the roof where it intersects with other surfaces or materials, such as where a roof plane meets a wall above, or at the eaves where the roof meets the gutter. In these cases, the adjoining surface could be the vulnerable component of the roof system.
Class A asphalt shingles are available in most parts of the country, and prices vary depending on the type you choose. Regardless of the type of roof you install, it must be kept in good condition and free of combustible debris. For a closer look at the interaction between buildings and wildfires, see Home Survival in Wildfire-Prone Areas: Building Materials and Design Considerations (University of California Davis, Agriculture and Natural Resources).
Photos by Steve Quarles
