What is the 25% rule for roofing, and does it apply in California?

Homeowners usually hear about the 25% rule from an insurance adjuster or a roofer who says a partial repair “triggers a full replacement”. The rule is real, but it is a Florida rule. California handles partial reroofs differently, and the threshold depends on where the house is.

Where does the 25% rule come from?

Section 706.1.1 of the Florida Building Code, Existing Building, says that no more than 25% of a roof may be repaired, replaced or recovered in any 12-month period unless the entire roof is brought up to current code. Florida narrowed the rule in 2022: if the existing roof was built to the 2007 Florida Building Code or later, only the repaired portion has to meet current code. The Florida Roofing and Sheet Metal Contractors Association explains the history.

Is there a 25% rule in California?

Not statewide. The reroofing section of the California Residential Code (R908) has no percentage trigger. It says that a roof replacement removes the old coverings down to the deck, and that a new layer may not go over a roof that already has two or more layers. Where 25% does appear in California, it is usually a local permit threshold. The City of San Jose, for example, requires a reroof permit once 25% or more of a roof is reroofed within any 12-month period, and treats smaller work as a repair.

What about wildfire zones?

Fire-zone rules use a different number. Section 507.1 of the 2025 California Wildland-Urban Interface Code says that when 50% or more of a roof is replaced in a 12-month period, the roof covering must meet the standard for new construction, which in these areas means a Class A fire rating. Any roofing added during a repair must also be at least Class A. Whether this applies depends on your address, which you can check on CAL FIRE’s Fire Hazard Severity Zone map.

How does this work in San Francisco?

The SF.gov reroofing permit page says you need a permit before installing, repairing or removing roofing material, and points to San Francisco Building Code Section 106A.2, item 13, for exempt work. Work that replaces structural parts such as framing or decking goes through an over-the-counter building permit instead. So in San Francisco the useful question is not “am I under 25%?” but “is this repair exempt, or does it need a permit?” We answer that on every job and pull the permit when one is needed. Our answer on permits for roof replacement in San Francisco has more detail.

Why does this matter for repair or replacement decisions?

Patching one section after another over a single year can cross a local threshold without anyone planning it, and in a fire zone it can commit you to upgrading the whole roof. If several areas are failing, compare the cost of repeated repairs with a planned roof replacement. If the damage is isolated, a targeted roof repair is usually the better call. A free roof inspection gives you photos and a written scope either way, and our page on roofing in San Francisco covers the city’s permit and street-space rules.