Class A is the top tier of roof-covering fire ratings under ASTM E108 / UL 790. It means the roof system resists severe fire exposure, prevents flame spread, and won’t generate burning brands that ignite neighboring structures.
California Building Code §705A.2 requires Class A on any new or replacement roof in a WUI Fire Hazard Severity Zone. CAL FIRE maintains the maps. In the Bay Area this includes large portions of Oakland Hills, Berkeley Hills, the Santa Cruz Mountains foothills, Marin County hills, the Santa Clara foothills, and most unincorporated hillside areas. Many cities (e.g., Los Altos Hills, Portola Valley) require Class A citywide regardless of WUI mapping.
Practical implication: nearly every architectural asphalt shingle, concrete tile, clay tile, and standing-seam metal roof we install achieves Class A as a complete system. The legacy 3-tab shingle and wood shake assemblies do not — which is why we no longer install them.
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