Garage conversion rules in San Mateo, 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 San Mateo per California ADU law. Building permit required. No replacement parking is required when converting a garage to an ADU under state law.
California state ADU law (SMMC Ch. 27.19 as updated) allows garage conversions to ADUs in San Mateo. A building permit is required. Replacement parking is not required when a garage is converted to an ADU per California Government Code §65852.2. The converted space must meet building code standards for habitable space. Contact Planning at (650) 522-7010 for pre-application guidance.
Unpermitted conversion: standard building code enforcement. Must bring to code or restore to garage. Safety violations: immediate correction.
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Side-by-side rule comparisons with other cities in San Mateo County.
See how other cities in San Mateo County handle garage conversions.
See how San Mateo's garage conversions rules stack up against other locations.
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