CLASS A ROOF REQUIREMENTS IN CALIFORNIA FIRE HAZARD SEVERITY ZONES

What a Fire Hazard Severity Zone is

The California Office of the State Fire Marshal maps Fire Hazard Severity Zones (FHSZ) in three classes — Moderate, High, and Very High — based on the likelihood and expected behavior of wildfire over a 30- to 50-year period, using fire history, vegetation, terrain, weather, and ember exposure. The State Fire Marshal classifies State Responsibility Areas directly; for Local Responsibility Areas (the cities and county land where local fire departments respond, which is nearly all of Orange and Los Angeles counties), the State Fire Marshal issues recommended maps that each city or county then adopts by ordinance.

New Local Responsibility Area maps were released in four phases between February 10 and March 24, 2025. Many Southern California cities gained Moderate and High zones for the first time and several saw their Very High zones expand. Your city's building or fire department, or the State Fire Marshal's online viewer, will tell you which zone — if any — your address falls in. Our city pages note which cities have mapped Very High zones.

When a re-roof must be Class A

The rule for existing homes is in the California Residential Code, and it is short. In a fire hazard severity zone, "the entire roof covering of every existing structure where more than 50 percent of the total roof area is replaced within any one-year period, the entire roof covering of every new structure, and any roof covering applied in the alteration, repair or replacement of the roof of every existing structure, shall be a fire-retardant roof covering that is at least Class A" (CRC R902.1.1). The same section allows a city to substitute the State Fire Marshal's model ordinance under Government Code §51189, so check with your building department if you are near a boundary.

Outside mapped zones the minimum is Class C (CRC R902.1.2). In practice, nearly every product we install — concrete and clay tile, GAF fiberglass asphalt shingles, most metal systems, and single-ply membranes — carries a Class A rating as part of a listed assembly, so the requirement is rarely a cost problem. What it rules out is untreated wood shake and shingle.

What "Class A" actually means

Roof coverings are fire-tested under ASTM E108 / UL 790, which exposes the assembly to flame, burning brands, and wind. Class A is the highest rating. Two points matter for a re-roof:

• Some products are Class A by themselves (concrete and clay tile, many fiberglass shingles). Others are Class A only as an assembly with a specific underlayment or cap sheet beneath them. Metal roofing and some synthetic shake products are in the second group.
• The rating follows the listing. If the manufacturer's Class A listing calls for a particular underlayment, the roofer has to install that underlayment, not a cheaper substitute.

What Chapter 7A adds for new construction

California Building Code Chapter 7A (and its residential twin, CRC Section R337) covers "materials and construction methods for exterior wildfire exposure." Its roofing section requires that "roof assemblies in the Fire Hazard Severity Zones shall be Class A rating when tested in accordance with ASTM E108 or UL790" (CBC 705A.1), and it adds details that a plain Class A rating does not:

• Profile tile: where the roofing profile leaves an air space over a combustible deck, a 72-lb ASTM D3909 cap sheet (or a Class A underlayment tested to ASTM E108) is required, bird stops are required at the eaves, and "hip and ridge caps shall be mudded in to prevent intrusion of fire or embers" (705A.2).
• Valleys: No. 26 gauge galvanized (or other corrosion-resistant) metal over a 36-inch-wide 72-lb mineral-surfaced cap sheet running the full length of the valley (705A.3).
• Gutters: "provided with the means to prevent the accumulation of leaves and debris" (705A.4).
• Vents: attic, eave, and ridge vents must be State Fire Marshal-listed flame- and ember-resistant vents or WUI vents tested to ASTM E2886 (706A.2); sloped-roof vents need noncombustible, corrosion-resistant mesh with openings between 1/16 and 1/8 inch (706A.2.1).

Scope matters. Chapter 7A applies to new buildings permitted on or after July 1, 2008 in a State Responsibility Area fire zone, a locally designated Very High zone, or a Wildland-Urban Interface area, and it exempts "additions to and remodels of buildings originally constructed prior to July 1, 2008" (701A.3). A re-roof of an older house is governed by the Class A rule in R902.1.1, not by every line of 7A — but cities can and do adopt stricter local amendments, and several Orange and Los Angeles County cities require ember-resistant vents on re-roofs in their Very High zones. We confirm the local rule with the building department before we write the scope.

What we recommend in a Very High zone

• A Class A listed assembly, installed exactly as listed — tile, fiberglass shingle, or metal over the specified underlayment.
• Ember-resistant vents whenever vents are replaced, even where not strictly required for a re-roof. Embers entering the attic are a leading way homes ignite.
• Metal valleys over cap sheet, bird stops at open tile eaves, and mortared or mechanically closed hips and ridges.
• Gutter guards or screens so leaves don't pile against the eave.
• Replacing any remaining wood shake, which cannot meet the standard without treatment and listing.

The permit application is where this gets decided. A roof permit in a mapped zone is reviewed against these requirements, and the final inspection checks them.

How to check your address

Start with your city. Most Orange and Los Angeles County cities posted their 2025 map and adoption ordinance on the fire or building department's website; several also have an address lookup. The State Fire Marshal's FHSZ page links to the statewide viewer and to each county's map data. If you are near a zone boundary, the building department's parcel lookup is the authority, because the zones are adopted parcel by parcel.