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3932 Woodcreek Lane San Jose, CA 95117

(408) 490-4248

Accessory Dwelling Unit (ADU) City Regulations for

San Mateo, CA

San Mateo is a city in San Mateo County, California. If visiting the area be sure to check out the San Mateo Japanese Gardens or spend the day visiting the Coyote Point Recreational Area.


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

Lot Size:


Maximum 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.

Number of Bedrooms:





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.


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.