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

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 trees or other vegetation that are well-pruned and maintained so as to effectively manage fuels and not form a means of rapidly transmitting fire from other nearby vegetation to a structure or from a structure to other nearby vegetation or to interrupt the advance of embers toward a structure. The intensity of fuels management may vary within the 100-foot perimeter of the structure, with more intense fuel reductions being utilized between 5 and 30 feet around the structure, and an ember-resistant zone being required within 5 feet of the structure, based on regulations promulgated by the board, in consultation with the department, to consider the elimination of materials in the ember-resistant zone that would likely be ignited by embers. The regulations may also alter the fuel reduction required between 5 and 30 feet to integrate the ember-resistant zone into the requirements of this section. Consistent with fuels management objectives, steps should be taken to minimize erosion, soil disturbance, and the spread of flammable nonnative grasses and weeds. For purposes of this subparagraph, “fuel” means any combustible material, including petroleum-based products, cultivated landscape plants, grasses, and weeds, and wildland vegetation.

(B) A greater distance than that required under subparagraph (A) may be required by state law, local ordinance, rule, or regulation. Fuel modification beyond the property line may only be required by state law, local ordinance, rule, or regulation in order to maintain 100 feet of defensible space from a structure. Fuel modification on adjacent property shall only be conducted following written consent by the adjacent landowner. Any local ordinance related to fuel modification shall be in compliance with all applicable state laws, regulations, and policies. Any local ordinance may include provisions to allocate costs for any fuel modification beyond the property line.

(C) An insurance company that insures an occupied dwelling or occupied structure may require a greater distance than that required under subparagraph (A) if a fire expert, designated by the director, provides findings that the fuel modification is necessary to significantly reduce the risk of transmission of flame or heat sufficient to ignite the structure, and there is no other feasible mitigation measure possible to reduce the risk of ignition or spread of wildfire to the structure. The greater distance may not be beyond the property line unless allowed by state law, local ordinance, rule, or regulation.

(2) Remove that portion of a tree that extends within 10 feet of the outlet of a chimney or stovepipe.

(3) Maintain a tree, shrub, or other plant adjacent to or overhanging a building free of dead or dying wood.

(4) Maintain the roof of a structure free of leaves, needles, or other vegetative materials.