California Wildland Urban Interface Code Information

California regulates wildfire risk to buildings with a two-pronged approach: maintain defensible space around the structure, and build the structure itself to resist ignition. This page collects the state codes, regulations, and standards behind both prongs.

Most catastrophic losses occur on hot, windy days when fire spreads faster than suppression forces can respond, and buildings ignite when embers land on receptive roofs, blow into vents, or lodge against combustible materials. The state's wildfire building standards exist to close those pathways. They work with, not instead of, defensible space: California law treats the parcel and the building as one system.

Building Standards: Chapter 7A

California Building Code Chapter 7A (and its residential counterpart, CRC Section R337), "Materials and Construction Methods for Exterior Wildfire Exposure," sets ignition-resistant standards for roofs, attic and foundation vents, eaves and soffits, exterior walls, windows and doors, and decking. It has applied to new construction in SRA fire hazard zones and LRA Very High zones since 2008, and the code is updated on the state's triennial code cycle. As the expanded 2024–2025 Fire Hazard Severity Zone maps are adopted locally, Chapter 7A applies to new construction in more of San Mateo County.

Listing with the State Fire Marshal is voluntary for most WUI products (wood shakes and shingles excepted). Unlisted materials can still qualify under Chapter 7A if test documentation is submitted to the local building official. Local jurisdictions may adopt stricter requirements, so confirm with your building department before designing a project.

Defensible Space Law: PRC 4291 and Zone 0

Public Resources Code 4291 requires 100 feet of defensible space (or to the property line) around buildings in the SRA and, through parallel provisions in Government Code, in LRA Very High Fire Hazard Severity Zones. Assembly Bill 3074 (2020) added the ember-resistant Zone 0 within 5 feet of structures; the Board of Forestry and Fire Protection is completing the implementing regulations, which phase in first for new construction in Very High zones. Our defensible space page explains the zone requirements in practice.

Development Standards: PRC 4290 and the Fire Safe Regulations

Public Resources Code 4290 directs the Board of Forestry to set minimum fire safety standards for development in the SRA and Very High LRA zones. The implementing "Fire Safe Regulations" (Title 14, California Code of Regulations, Division 1.5, Chapter 7, Subchapter 2, beginning at section 1270) govern road width and grade for emergency access, signing and addressing, emergency water supply, and fuel modification for new development.

Hazard Mapping: Government Code 51175–51189

Government Code sections 51175–51189 establish Fire Hazard Severity Zone designation in Local Responsibility Areas. The State Fire Marshal identifies the zones; local jurisdictions adopt them by ordinance. Current maps and the address lookup tool are on the OSFM Fire Hazard Severity Zones page, and county-specific information is on the San Mateo County planning site.

Getting Code Questions Answered

The Office of the State Fire Marshal publishes information bulletins and formal code interpretations for the wildfire protection building codes. Project-specific questions belong with the agency having jurisdiction: your city or county building department and your local fire agency, which may enforce more restrictive local ordinances. See our San Mateo County fire codes page for local agency contacts.