Accessory Structures in San Mateo, CA (2026)
5 verified accessory structures rules for San Mateo, California, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
San Mateo allows ADUs in all residential zones (SMMC Ch. 27.19). One-bedroom ADUs up to 850 sq ft; two-bedroom up to 1,000 sq ft; detached max 16 ft plate/24 ft peak; 4-ft setbacks. ADUs cannot be STRs.
City of San Mateo ADU Rules
Some RestrictionsShed Rules
Small accessory structures (sheds) in San Mateo must comply with SMMC zoning setbacks. Sheds under 120 sq ft and under 8 feet average height generally do not require a building permit but must comply with zoning requirements.
City of San Mateo Shed Rules
Some RestrictionsGarage Conversions
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.
City of San Mateo Garage Conversion Rules
Some RestrictionsCarport Rules
Carports in San Mateo require a building permit under Title 23 and must comply with the zoning standards in Title 27. Carports count toward lot coverage calculations. Garage or carport conversions to ADUs are specifically addressed under Chapter 27.19.
San Mateo Carport Regulations
Some RestrictionsTiny Homes
Tiny homes in San Mateo are regulated through the ADU provisions of Chapter 27.19 and California Government Code 65852.2. Tiny homes on permanent foundations may qualify as ADUs (up to 1,200 sq ft detached) or JADUs (up to 500 sq ft). Tiny homes on wheels are classified as RVs and cannot serve as permanent housing.
San Mateo Tiny Home & Small Dwelling Rules
Some RestrictionsLooking for San Mateo County county-wide rules?
County ordinances apply to unincorporated areas and may supplement San Mateo city rules.
Accessory Structures in San Mateo County →