San Mateo County, CA Fire Regulations: Brush Clearance (2026)
Key Facts
- Governing law
- California Public Resources Code section 4291
- Defensible space distance
- 100 ft around structures
- Zone 1 (home defense)
- 0-30 ft - lean, clean, green
- Zone 2 (reduced fuel)
- 30-100 ft - grass cut to 4 in max
- Roadside clearance
- 13 ft 6 in vertical, 10 ft from road edge
- Inspections / contact
- San Mateo County Fire Marshal, (650) 573-3846
Summary
Properties in the Wildland-Urban Interface of unincorporated San Mateo County must maintain defensible space under California Public Resources Code 4291: 100 feet of clearance around structures. CAL FIRE / San Mateo County Fire conducts defensible space inspections, and roadside vegetation must be cleared to specified clearances.
4291. (a) A person who owns, leases, controls, operates, or maintains a building or structure in the state responsibility area shall at all times do all of the following: (1) (A) Maintain defensible space of 100 feet from each side and from the front and rear of the structure, but not beyond the property line, except as provided in subparagraph (B). The amount of fuel modification necessary shall consider the flammability of the structure as affected by building material, building standards, location, and type of vegetation. Fuels shall be maintained and spaced in a condition so that a wildfire would be unlikely to ignite the structure. This subparagraph does not apply to single specimens of
Full Breakdown
Unincorporated San Mateo County, including the high-risk Santa Cruz Mountains and coastal hills, falls largely within CAL FIRE's wildland fire protection responsibility. Under California Public Resources Code (PRC) section 4291, owners of buildings in or near wildland or designated fire hazard severity zones must maintain defensible space; the clearance requirement around buildings and structures was expanded from 30 feet to 100 feet. The standard defensible-space model is two zones totaling 100 feet: Zone 1 (the home-defense zone) extends 30 feet out from buildings, decks, and structures (remove dead vegetation, keep tree branches at least 10 feet apart, relocate wood piles), and Zone 2 (the reduced-fuel zone) extends from 30 feet out to at least 100 feet or the property line (cut grass to a maximum of 4 inches and create vegetation spacing).
California is also phasing in a Zone 0 ember-resistant requirement for the first 0-5 feet under recent legislation. gov or (650) 573-3846. Roadside vegetation clearance requires removing flammable vegetation to a vertical clearance of 13 feet 6 inches and 10 feet from the roadway edges. The county also offers AB-38 defensible space inspections (required before certain home sales in high fire areas).
Violations & Fines
Failure to maintain defensible space under PRC 4291 is enforced by CAL FIRE / the San Mateo County Fire Marshal, who may inspect properties in the WUI, issue notices to abate, and re-inspect. Under state law, the local fire agency may abate hazardous vegetation and recover costs if the owner fails to comply after notice. Report fire hazards or request a defensible space inspection at (650) 573-3846 or SMCFDFireMarshal@fire.ca.gov.
Frequently Asked Questions
How much defensible space do I need in unincorporated San Mateo County?
Who inspects defensible space here?
Do I have to clear vegetation along my road?
Sources & Official References
Other rules in San Mateo County
California rules heatmap·Compare San Mateo County to another location·View the California fire regulations overview
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