California county profile
San Mateo County spans coast, peninsula ridge, and Santa Cruz Mountain foothills — and its western coastside falls under certified coastal rules while its hillside properties face some of the Bay Area's shorter construction windows and a tree ordinance substantially consolidated just recently.
The county's recently consolidated Protected Tree Ordinance is not effective in the Coastal Zone — separate heritage tree provisions apply there instead, so the same removal that needs one kind of permit inland requires a different process at the coast.
Properties in the Residential Hillside zoning district are protected by a lower tree trunk-size threshold than the rest of the county — so hillside homeowners may face permit requirements for trees that wouldn't be protected on a flatland parcel.
Construction in unincorporated San Mateo ends in the early evening on weekdays, starts later on Saturdays, and is prohibited on Sundays and most holidays — among the more restrictive construction-hour schedules in the Bay Area.
The entire western coastside — including Montara, Moss Beach, El Granada, and Pescadero — requires a Coastal Development Permit for most new development, stacked on top of county building permits.
The first habitat conservation plan adopted in the country covers a specific area around San Bruno Mountain, protecting several rare butterfly and snake species — new development in or near that area may trigger mitigation requirements not apparent from standard county zoning.
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Screen an addressSource: Headlands Environmental — environmental site screening for California. Rules summarized from publicly available county codes and planning documents; project review counts indexed from the State Clearinghouse. For authoritative requirements, consult San Mateo County directly.