What a re-roof in Diamond Bar has to comply with

What California requires everywhere

State-level requirements sit underneath everything above. They are included because more than one of them is commonly misstated, and because a homeowner who knows them can tell a careful quote from a careless one.

The code your roof will be built to

California re-roofs are built to Title 24, the California Building Standards Code. The 2025 edition took effect on 1 January 2026 and applies to any project whose permit application was made on or after that date. If your last roof went on before then, it was built to a different edition, and some of what was acceptable on it is not acceptable now.

That matters practically rather than academically: a contractor quoting from habit rather than from the current code will occasionally quote a detail that will not pass inspection, and the inspection is at the end of the job rather than the beginning.

Fire classification: what is actually required, and where

The statewide floor is a Class C fire-retardant roof covering. That applies to a new roof, to any repair or replacement, and to any existing building where more than half the roof area is replaced within a year — which is every ordinary re-roof.

Class A, the highest classification, is required where the property sits inside a fire hazard severity zone or a wildland-urban interface area, and many cities require it more widely by local ordinance. In practice, across most of south Orange County, Class A is the answer — but it comes from the fire zoning and the local ordinance rather than from a blanket statewide rule, so it is worth confirming for your address rather than assuming either way.

As of 1 January 2026 the wildfire rules live in their own book: the California Wildland-Urban Interface Code, Title 24 Part 7, which consolidated what used to be Chapter 7A of the building code and section R337 of the residential code. A contractor still citing Chapter 7A is citing something that has been superseded.

Tear-off waste and where it goes

CALGreen requires 65 per cent of nonhazardous construction and demolition waste to be diverted from landfill — but that chapter applies to additions and alterations that increase a building's conditioned area, volume or size, and a straight re-roof does not. So the state mandate generally does not reach a re-roof.

Local ordinances frequently do, and the state code expressly lets a city be stricter. Plenty of cities capture roofing through their own construction and demolition rules by permit valuation, which can mean a deposit and a diversion report on an ordinary house. Ask the city before the skip is ordered rather than after.

What a wildfire-zone roof actually has to include

In a mapped fire hazard zone the requirements reach well past the covering, and they are the details that separate a compliant roof from a cheap one. Embers, not flame fronts, are what destroy most houses in a wildfire, and every one of these requirements is about closing a gap an ember could get through.

• A roof assembly meeting Class A when tested to ASTM E108 or UL 790
• On profiled tile, bird stops at the eaves and hip and ridge caps mudded in, so there is no open end for embers to enter
• Valley flashing of at least 0.019 inch (26 gauge) corrosion-resistant metal, over a mineral-surfaced cap sheet at least 36 inches wide
• Noncombustible gutters and downspouts, with an approved means of stopping leaves and debris collecting in them
• Vent screening of noncombustible corrosion-resistant mesh, no finer than 1/16 inch and no coarser than 1/8 inch

How many layers can stay on

A new covering may not be laid over the old one where there are already two applications of any type on the roof, where the existing roof or covering is water-soaked or has deteriorated enough that it is no longer a sound base, or where the existing covering is slate, clay, cement or asbestos-cement tile. In those cases the roof comes off to the deck.

Two layers is therefore the practical ceiling, and on an older house nobody knows how many are up there until somebody looks. That is the single most common reason a re-roof price changes after the work starts, and it is a fair reason to ask for the quote to state what happens if a third layer appears.