SAN MATEO, CA
Accessory Dwelling Unit (ADU) City Regulations
ADU: R1-A, R1-B, R1-C, R2, R3, R4, R5, R4D, R5D, R6D and BMSP
Junior ADU: R1-A, R1-B, R1-C, and R2
ADU Floor Area:
ADU: 640 sq.ft. max
Junior ADU: 500 sq.ft. max
Note: floor area counts against total floor area allowed on a parcel. Total floor area of both ADU and primary dwelling must not exceed max. allowed for underlying zoning district.
No. of Bedrooms:
Storage / Closet:
Kitchen / Bath:
ADU: Requires separate bathroom and kitchen facilities (permanent range, counters, refrigerator, and sink).
Junior ADU: Requires separate “efficiency” food preparation area.
ADU: One off-street parking space per unit or bedroom, whichever is less. State parking exceptions apply. Parking spaces must be 10’ by 18’ without obstructions. Tandem parking allowed.
Junior ADU: No additional parking required.
ADU: must comply with underlying zoning district. No setbacks required for existing legally converted garages or other accessory structures. For ADUs constructed above a garage, a 5’ setback is required from side and rear lot lines.
Junior ADU: must comply with underlying zoning district.
Must comply with the underlying zoning district.
ADU: Must be oriented to keep windows offset from neighboring dwellings to preserve privacy. Must be designed to minimize visibility from the street, except on corner lots.
Junior ADU: By definition is located wholly within the walls of an existing dwelling, and must include the conversion of an existing bedroom.
Rear Yard Coverage:
Must adhere to requirements of underlying zoning district.
Materials / Design:
Must have similar design elements, colors, and materials as the existing dwelling.
ADU: Must have independent access from primary dwelling and cannot be closer to the street than the primary dwelling.
Junior ADU: Must have an independent entrance from primary dwelling and must have access to the common living areas of the primary dwelling which can be provided by a double lock door.