San Mateo County, CA Fire Regulations: Brush Clearance (2026)

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. The San Mateo County Fire Marshal's Office offers defensible space inspections within the Wildland-Urban Interface (WUI) and can be reached at SMCFDFireMarshal@fire.ca.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).