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San Carlos, California: ADU Regulations

City or County:

San Carlos, California

Date Updated:



Residential (R) zoning districts, mixed-use (MU) zoning districts and in any planned development (PD) zoning district where residential uses are permitted or conditionally permitted as part of an approved planned development plan. 

Junior only in the single-family (RS) zoning districts within an existing single-unit dwelling, or as part of a proposed new single-unit dwelling.

Types of ADUs:

Attached, Detached, Junior



Lot Size:

No min/max as long as lot abides by zone standards.

Maximum ADU Floor Area:

Studio and 1 bedroom: 850 sq.ft.

More than 1 bedroom: 1000 sq.ft.

JADU: limited 500 sq.ft. in size; cannot be smaller than the size required to allow an efficiency unit pursuant to Health and Safety Code Section 17958.1.

If the ADU does not meet all development standards of the applicable zoning district, the maximum floor area permitted is 800 sq.ft, regardless of number of bedrooms.

Lot Coverage:

Must abide by underlying zone standards.


No min/max (provided there are separate, independent living quarters for one household).


No min/max


Require separate kitchen facilities (permanent range, counters, refrigerator, and sink).


Require separate bathroom facilities. JADU can share sanitation facilities with the single-unit dwelling.

Note: Drainage and sewer connections should be assessed on a project by project basis.


One on-site parking space must be provided for ADU in addition to parking required for primary residence. Tandem parking allowed.


Attached: must adhere to underlying zoning district's setbacks.

Detached: must maintain a min. of 5’ from side and rear lot lines and must also conform to setbacks established in underlying zoning district.

Note: Fire Department regulations should be assessed on a project by project basis.


Cannot exceed 16' unless located over a garage, wherein max. height allowed is 20'.

Attached, Junior: same as zone

Rear Yard Coverage:

Must follow requirements established by zoning district in which lot is located and any other applicable City codes.


Residential design, exterior materials and colors, roof pitch and style, type of windows, and trim details of ADU shall be substantially the same as and visually compatible with primary dwelling.

Junior accessory dwelling units shall satisfy applicable design criteria and conform to any applicable design guidelines.

Balconies, decks, and open stair landings shall not face the side property lines, except as needed to allow ingress and egress.

Note: Historic Neighborhoods or Districts should be assessed on a project by project basis.


Doors and windows for detached ADUs must be located at least 10' from an interior side or rear lot line. Attached ADUs do not have such a requirement.

JADUs must have a separate external entrance from the primary dwelling. The entrance cannot face a street unless ruled unfeasible Community Development Director.

Owner Occupancy:

Required for Junior. Waived for others until 2025.

Source Code:

Important Note: Rules and regulations are updated and changed frequently. It’s one of our jobs to be up to speed and navigate those regulations. Let us know if our website isn’t up to date or if you have any information that could help. Cheers!