Wildfire Urban Interface Codes Have Changed
by Richard K. Olson, president & technical director, Tile Roofing Industry Alliance
(Editor’s Note: Richard K. Olson is president and technical director for the Tile Roofing Industry Alliance. The association represents industry professionals involved in the manufacturing and installation of concrete and clay tile roofs in the United States and Canada, and works with national, state, and local building officials to develop installation techniques, codes, and standards for better roofing systems. Olson can be reached at firstname.lastname@example.org.)
For those of us in the West, last winter’s weather provided one of the greatest snowpacks in decades. While this will be helpful for the reduction in potential water shortage, it does not necessarily translate to a safer fire season this summer. The wet weather allowed the growth of underbrush and grasses that, when dry, create additional ladder fuel for wildfires later in the summer. In Oregon, the Forest Service is predicting another extremely dry and hot summer that, when combined with the new undergrowth fuel sources, may keep fire danger levels on high alert well into October.
In response, local code officials in many areas are expanding the Wildfire Urban Interface (WUI) designated areas into even more populated areas. Once only for true rural areas, we are now seeing the WUI codes migrating into major cities as urban growth boundaries expand and buildings are being built into mountainous regions that were once forest areas. Roofing professionals need to better understand the requirements for roof assemblies in these WUI areas, as changes have occurred in the last year.
The following information is provided for guidance only and it is the responsibility of the installer to check for any code revisions, product manufacturers recommendations and to ensure your final installation is code compliant. For specific fire language, the following is taken from the 2022 California Building Code Chapter 7A, 705A Roofing.
Roofs shall have a roofing assembly installed in accordance with its listing and the manufacturer’s installation instructions. Roof assemblies in the Fire Hazard Severity Zones shall be Class A rating when tested in accordance with ASTM E108 or UL790.
Where the roofing profile has an airspace under the roof covering, installed over a combustible deck, a 72-lb. cap sheet complying with ASTM D3909 is required. The standard specification for asphalt-rolled roofing surfaced with mineral granules shall be installed over the roof deck. Bird stops shall be used at the eaves when the profile fits, to prevent debris at the eave. Hip and ridge caps shall be mudded in to prevent intrusion of fire or embers.
A cap sheet is not required when no less than 1” of mineral wool board or other noncombustible material is located between the roofing material and wood framing or deck. Alternately, a Class A fire rated roof underlayment, tested in accordance with ASTM E108, shall be permitted to be used. If the sheathing consists of exterior fire-retardant-treated wood, the underlayment shall not be required to comply with a Class A classification.
Where valley flashing is installed, the flashing shall be not less than 0.019” No. 26 gage galvanized sheet corrosion-resistant metal installed over not less than one layer of minimum 72-lb. mineral-surfaced non-perforated cap sheet complying with ASTM D3909, at least 36”-wide running the full length of the valley.
Roof gutters shall be provided with the means to prevent the accumulation of leaves and debris in the gutter.
The Tile Roofing Industry Alliance (TRI) is the industry association for the clay and concrete roof tile manufacturers in the United States. As a collective organization, we address many of the important issues and technical positions for our members. In the area of fire ratings, the TRI has been instrumental in the development of code and test procedures.
Our roof tile manufacturer members perform fire-rating tests as outlined in the IRC/IBC and other regional code requirements including the Wildfire Urban Interface areas per the 2022 California Residential Code and the California Building Code.
The testing of both the burning brand and spread of flame test procedures will provide the final fire class rating that will be placed in formal code issued product approvals. For any questions, please refer to the clay or concrete roof tile manufacturers formal code approval for fire rating classifications and special installation requirements for accessories or product needs.