Garage conversion rules in San Mateo County, CA — sometimes called garage-to-ADU or accessory living unit conversions — govern permits, ceiling height, egress, and parking replacement.
Garage conversions to ADUs are permitted in unincorporated San Mateo County per California ADU law. Building permit required. No replacement parking required. Coastal Zone conversions need a Coastal Development Permit.
California state ADU law allows garage conversions to ADUs or JADUs in unincorporated San Mateo County. A building permit is required. Replacement parking is not required when converting a garage to an ADU under state law. The converted space must meet building code for habitable space. Properties in the Coastal Zone require a Coastal Development Permit in addition to the standard building permit. Contact Planning & Building at (650) 363-4161.
Unpermitted conversion: standard building code enforcement. Must bring to code or restore to garage. Safety violations: immediate correction.
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See how San Mateo County's garage conversions rules stack up against other locations.
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