Campbell CA ADU Guidelines

Accessory Dwelling Unit (ADU) City Regulations


Attached/Detached:  R1

Lot Size:

Minimum 10,000 sq. ft.

Maximum ADU Floor Area:

Lot Size Max Floor Area
10,000—10,999 sq.ft.700 sq.ft.
11,000—11,999 sq.ft.800 sq.ft.
12,000—12,999 sq.ft.900 sq.ft.
13,000—13,999 sq.ft.1,000 sq.ft.
14,000—14,999 sq.ft.1,100 sq.ft.
+15,000 sq.ft.1,200 sq.ft.

(Note: in no case shall living area for attached or interior ADU exceed 50% of existing primary dwelling unit.)

Number of Bedrooms:

Maximum two bedrooms.


No minimum/maximum


Maximum 1 kitchen (with permanent provisions for cooking and eating)

Maximum 2 bathrooms


  1. Interior ADU: no additional parking required.
  2. Attached/Detached ADU: one parking space per bedroom; exceptions apply.
  3. Garage Conversion: any existing parking spaces that are removed by conversion to be replaced concurrently with creation of accessory dwelling unit.

Uncovered parking spaces required for accessory dwelling unit may encroach into required front-yard or street-side yard setback within existing driveway that satisfies the min. stall dimensions for a residential parking space, unless such configuration is determined not to be feasible based upon fire and/or life safety conditions present on property.

Parking Exceptions:

No parking space is required if unit:

  1. Is located within one-half mile of public transit.
  2. Is located within a designated historic district.
  3. Is located within boundaries of permanent residential parking permit program, and where the City does not offer parking permits to the occupant(s) of the ADU.
  4. Is located within one block of a City-licensed car-share vehicle.


Attached/Detached: must comply with min. requirements of zoning district.


Attached: must comply with standards of underlying zoning district.
Detached: single story 14' maximum.


Attached or interior ADU limited to the ground floor or the basement of the primary dwelling and must maintain appearance of primary dwelling as that of a single-family dwelling. Spacing between structures and lot coverage guidelines of zoning district apply.

Rear Yard Coverage:

Must comply with maximum allowable yard coverage of zoning district.


Detached must incorporate same or similar building materials and colors as primary dwelling, except for manufactured homes, which are required to incorporate only same or similar building colors as the primary dwelling.

ADUs converted from garages to include removal of garage doors, to be replaced with architectural features that remove any appearance that structure was originally a garage.


Must include separate exterior access from primary dwelling. Front door cannot be oriented towards public street.

Can I construct a new house and an ADU at the same time?

Yes. However, a detached ADU requires a separate building permit. Additionally, a Certificate of Occupancy will not be granted for the ADU until the new house is completed.

So unfortunately they don’t allow you to live in the ADU first while the main house is being constructed, if both are new construction. Also, if you build both the primary house and the ADU at the same time, you have to still adhere to the 40% Maximum Lot Coverage Ratio and 45% Max Floor Area Ratio, but if you build the ADU after the primary house has been completed and permit finalized with CO, then you are allowed to exceed that 40% Max Lot Coverage and 45% Max Floor Area Ratio as long as the ADU does not exceed 800 sq. ft. (see top right of Page 1). I also called Campbell Planning Dept. and they’ve verified both of the above.

For more ADU information:


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