As fires increase in frequency and intensity, ignition-resistant construction and materials grow exponentially in importance. Fire-resistant homes and structures must incorporate a suite of combined solutions. One key area of focus is the roof, as it is a common ignition point for a fire’s flying embers.
As a fire burns, embers, or fire brands, are pushed by the winds generated by the fire. The type of fire determines the amount of embers produced, as well as the distance they ultimately travel. Embers can carry enough heat energy to ignite combustible structures as they blow against, or land upon, the surfaces of a home or structure.
Science supporting the critical need for ignition-resistant construction specifically features Class A roofing, among other items such as screened attic vents and composite decking, as a significant defense against ember-initiated ignition of homes and structures.
Class A roofs encompass not just the covering material, but also the overall assembly, and are tested by a third-party lab, which subjects the roofing assembly to a fire brand test. To be deemed Class A, the fire cannot penetrate the roof or cause the structure or underlayment to ignite before the brand is consumed and burns out during the test. Stone-coated steel roofing is a Class A roofing material that is proven to provide ignition resistance.
State-by-state building codes address ignition-resistant Class A roofing. For example, current building code in California, a state known for fire risk, states roofs shall have an assembly installed in accordance with its listing and the manufacturers’ installation instructions (for some manufacturers, this may require the roof assembly include a specific underlayment).
Per manufacturer guidance, many stone-coated steel panels can be installed either on a batten or direct-to-deck, usually when the existing sub-deck is solid or spaced sheathed, eliminating the batten needing to act as the panel support. Today’s panel designs also allow for exposed or hidden fastening systems.
Roof gutters are also addressed in California’s code, which states they must be provided with the means to prevent accumulation of leaves and debris. Stone-coated steel roofs, in particular, can use gutter guards in a fine mesh to allow water into the gutter but prevent leaves and debris from entering.
California’s building code also advises on roof coverings, stating where the roof profile allows a space between the roof covering and roof decking, the spaces shall be constructed to prevent the intrusion of flames and embers, be fire-stopped with approved materials, or have one layer of minimum 72-pound mineral surfaced non-perforated cap sheet complying with ASTM D3909 installed over the combustible decking.
Finally, California code includes roof valleys, stating that, where valley flashing is installed, flashing shall not be less than 0.019-inch No. 26 galvanized sheet corrosion-resistant metal installed over not less than one layer of minimum 72-pound mineral surfaced non-perforated cap sheet complying with ASTM D3909, at least 36-inch-wide running the full length of the valley. Notably, all stone-coated steel roofs utilize a corrosion-resistant steel valley metal formed to a specific shape to shed water off the roof.
Pete Croft is the business development and brand manager at Houston-based Westlake Royal Roofing Solutions, representing the Unified Steel stone-coated roofing product line. Visit www.westlakeroyalroofing.com for more information.