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San Carlos, California: ADU Regulations

City or County:

San Carlos, California

Date Updated:



Any Single-family residential zoning district.

*ADUs are permitted only on lots with access from a roadway that meets California Fire Code Section 902.2.2.1

Types of ADUs:

Attached, detached



Lot Size:

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

Maximum ADU Floor Area:

Attached: may be 30% of the home's square-footage in area up to 1,200 sq.ft. max.

Detached: limited to 640 sq.ft. max

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.

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 15' unless located over a garage, wherein max. height allowed is 28'.


Attached: may be located within existing primary residence.

Detached: may be located on rear half of lot and may be second floor of garage provided secondary unit maintains underlying zoning districts established setbacks. Additionally, there can be no other ADU within 400' measured from nearest edge of lot line of each respective or proposed second dwelling unit (may be waived by Director upon review).

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.

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.

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!