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

Since January 1, 2026, roofing in California is governed by the 2025 edition of Title 24, and the re-roof rule for mapped zones now lives in two places that point at each other:

• The Residential Code hands off to the wildfire code. "Roofing requirements for structures located within Fire Hazard Severity Zones or in a Wildland-Urban Interface (WUI) area shall also comply with Part 7, California Wildland-Urban Interface Code" (CRC R902.1.1).
• The wildfire code sets the re-roof trigger. The roof covering on an existing building that is "replaced or [has] 50 percent or more replaced in a 12-month period shall be replaced with a roof covering required for new construction in accordance with Sections 504.2 and 504.2.1," and "all portions of a roof covering applied during an addition, alteration or repair to an existing structure shall meet at least a Class A fire classification" (CWUIC 507.1).

Section 504.2 is the Class A requirement, and Section 504.2.1 adds the air-space details for profile tile described below. Two things to notice compared with the code it replaced: the threshold is now 50 percent or more (the old Residential Code rule said more than 50 percent), and Section 507.1 expressly pulls the air-space details of 504.2.1 into a re-roof, so a Class A label on the tile alone is not the whole requirement. The statute behind all of this, Health and Safety Code §13132.7, still sets the floor — at least Class A in a Very High Fire Hazard Severity Zone, whether the zone was designated by the State Fire Marshal or by your city, unless the city has adopted the State Fire Marshal's model ordinance under Government Code §51189 instead — so check with your building department if you are near a boundary.

Outside mapped zones the minimum on a re-roof 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 the Wildland-Urban Interface Code adds

Through 2025 these rules were Chapter 7A of the California Building Code (and Section R337 of the Residential Code). The 2025 code cycle deleted Chapter 7A and moved its requirements into a new Part 7 of Title 24, the California Wildland-Urban Interface Code (CWUIC), effective January 1, 2026. The roofing provisions are now in Chapter 5:

• Class A assembly (504.2): "Roofs shall have a roof assembly that complies with a Class A fire classification when tested in accordance with ASTM E108 or UL 790." Clay or concrete tile, slate, and metal on a noncombustible deck are deemed Class A without testing; over a wood deck, the assembly listing governs.
• Profile tile and other coverings with an air space (504.2.1): over a combustible deck, either a 72-lb ASTM D3909 cap sheet on the deck (504.2.1.1) or a listed underlayment tested as part of a Class A assembly (504.2.1.2). Either way, "bird stops shall be used at the eaves where the profile fits" and "hip and ridge caps shall be mudded in to prevent intrusion of fire or embers."
• Valleys (504.2.2): No. 26 gauge (0.019-inch) corrosion-resistant metal over a 36-inch-wide 72-lb mineral-surfaced, nonperforated ASTM D3909 cap sheet running the full length of the valley.
• Gutters (504.4): noncombustible gutters and downspouts, "provided with an approved means to prevent the accumulation of leaves and debris."
• Vents (504.10): attic, eave, ridge, and underfloor vents must be Wildfire Flame and Ember Resistant vents listed by the State Fire Marshal or WUI vents tested to ASTM E2886 (504.10.1); vents on a sloped roof, such as dormer vents, need noncombustible, corrosion-resistant mesh with openings between 1/16 and 1/8 inch (504.10.2).

Scope matters. The full code applies to new buildings permitted on or after July 1, 2008 in any State Responsibility Area fire zone (Moderate, High, or Very High), in a Very High zone designated by a city or county, or in a locally designated wildland-urban interface area, and it exempts "additions to and remodels of buildings originally constructed prior to July 1, 2008" (CWUIC 101.3.1, 101.3.1.1). A re-roof of an older house is governed by Section 507.1, which reaches back only to Sections 504.2 and 504.2.1 — the Class A assembly and the air-space details — not to the valley, gutter, and vent sections. Cities and counties can amend the code locally, and the State Fire Marshal's own guidance is to consult the local building official; for the Moderate and High zones that many cities mapped for the first time in 2025, the city's adopting ordinance decides what applies. 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.
• State Fire Marshal-listed ember-resistant vents whenever vents are replaced, even though Section 507.1 does not require them on a re-roof by itself. Embers entering the attic are a leading way homes ignite.
• Metal valleys over cap sheet, bird stops at open tile eaves, and mudded-in hips and ridges — the last two are required on a fire-zone re-roof of profile tile (504.2.1).
• 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.