Class A Roofs, Vents and Gutters in LA.

Embers are the main threat to a roof in a wildfire. The LA County Fire Department says a roof "can easily catch fire from windblown embers." The building rules for fire zones are built around that fact. They cover the roof covering, the gaps under it, the valleys, the gutters and the vents. Part of our wildfire roofing hub.

This page walks through those rules. Our main source is LA County Building and Safety's 2026 standard construction notes for Fire Hazard Severity Zones. They are based on the 2025 California Wildland-Urban Interface Code, Chapter 5. Your city may publish its own version. LA Roof Guide does not do roof work. This is general information only.

When these rules apply

The county notes list where they apply:

1. New buildings.
2. "Additions, alterations or repairs made to existing buildings within Wildland-Urban Interface (WUI) Fire Area or Fire Hazard Severity Zone."
3. Any WUI Fire Area designated by the LA County Fire Department.

So a reroof on an existing home in a zone counts. To check whether a home is in a zone, see fire hazard severity zones in LA.

CALBO notes that since January 1, 2026, these rules sit in a standalone code, Title 24, Part 7. Before that they were spread across the building, residential and fire codes. The county notes say the same: wildfire construction provisions "are now located in Part 7, California Wildland-Urban Interface Code."

Rule 1: A Class A roof covering

The county notes say: "Roof covering shall be Class A fire classification when tested in accordance with ASTM E108 or UL790." ASTM E108 and UL 790 are the fire test standards the notes name.

The notes list a few exceptions. They include roofs of brick, masonry or exposed concrete, and some metal, clay tile, concrete tile or slate roofs installed on noncombustible decks. Ask your building department how these apply to your roof.

In the City of Los Angeles, the LADBS express reroof permit says: "Class A roof covering is required within Very High Fire Hazard Severity Zone (VHFHSZ)."

LA County Fire's advice points the same way: "Build your roof or re-roof with fire-resistant materials that include composition, metal, or tile." It also warns that "homes with wood shake or shingle roofs are at a higher risk of being destroyed during a wildfire." For more on materials, see asphalt shingle vs tile roofs.

Rule 2: Close the gap under the covering

Some roof profiles leave open space between the roof covering and the deck below. The notes treat that space as a path for flames and embers.

The county notes require that space to be built "to prevent the intrusion of flames and embers." The options listed are:

• Fire stop the spaces with approved materials, or
• Install "one layer of 72-pound cap sheet complying with ASTM D3909" over the roof deck.

There is an exception. The cap sheet is not needed where at least 1 inch of mineral board or other noncombustible material sits between the roofing and the wood framing or deck.

LA County Fire gives the same advice in plain terms: "Block any spaces between roof decking and covering to prevent ember intrusion."

Rule 3: Valley flashing

Valleys are where two roof slopes meet. Where valley flashing is installed, the county notes require:

• Flashing of at least "0.019-inch No. 26 gage galvanized sheet."
• Installed over at least one layer of 72-pound mineral-surfaced, non-perforated cap sheet complying with ASTM D3909.
• That cap sheet at least 36 inches wide, running the full length of the valley.

Rule 4: Noncombustible gutters with a debris guard

The county notes say: "Roof gutters and downspouts shall be constructed of noncombustible material. Gutters shall be provided with an approved means to prevent accumulation of leaves and debris."

LA County Fire adds the upkeep side: "Clear pine needles, leaves, and other debris from your roof and gutters." It also says to "screen or enclose rain gutters to prevent accumulation of plant debris."

Rule 5: Ember-resistant vents

Attic and eave vents are a way in for embers. LA County Fire says vents "are particularly vulnerable to flying embers."

The county notes require vents for "enclosed attics, enclosed eave soffit spaces, enclosed rafter spaces, and underfloor vents" to resist ember and flame intrusion. A vent must meet one of two options:

• A listed vent complying with State Fire Marshal and WUI rules and ASTM E2886, or
• "Corrosion resistant, noncombustible wire mesh with min. 1/16 inch and max. 1/8 inch openings."

Vents on a sloped roof, such as dormer vents, must have openings between 1/16 and 1/8 inch, be corrosion resistant, and be noncombustible. The notes allow one exception for vents under the roof covering along the ridge that use noncombustible wire mesh.

The notes also say vents "shall NOT be installed on underside of eaves and cornices" unless certain code conditions are met.

LA County Fire warns against plastic screens: "Do not use fiberglass or plastic mesh because they can melt and burn."

Rule 6: Eaves

Open eaves expose the underside of the roof. The county notes list approved ways to protect exposed roof decks under unenclosed eaves, such as noncombustible or ignition-resistant materials. LA County Fire suggests to "box-in eaves with non-combustible materials to prevent accumulation of embers."

What does not count

The county notes are direct: "The use of paints, coating, stains or other surface treatments are not an approved method of protection." A fire-retardant spray does not stand in for a code-approved material.

Upkeep checklist from fire officials

From LA County Fire and the City of Santa Monica:

• Keep roofs, gutters and decks clear of leaves and needles.
• Cut tree branches back at least 5 feet from the roof.
• Keep branches at least 10 feet from a chimney (oak trees excepted).
• Cover chimney and stovepipe outlets with a nonflammable screen of 1/8 inch wire mesh or smaller.
• Use 1/8 inch mesh on openings, per Santa Monica's guidance.

Questions for your building department

• Is my home in a zone, and at what level?
• Which roof coverings meet Class A for my roof type?
• Will my reroof require vent, gutter or eave upgrades?

For the permit steps, see reroof permit basics.

This page is general information, not legal, engineering or building code advice. Rules differ by city; check with your local building department.