ADU Regulations and Zoning in San Diego County

– Only structures/rooms within the existing or proposed multifamily complex that are not used as livable space, including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages, can potentially be converted at least into one ADU, or multiple ADU’s, up to 25% of the existing multifamily dwelling units.

– Up to two detached ADU’s may be permitted, per lot that has an existing or proposed multifamily complex if the following requirements are met.

1. The addition of two detached ADU’s is not subject to any nonconforming regulations.
2. A non-conforming multifamily complex can have up to two detached ADU’s or may have ADU’s created within the existing multifamily complex (not both) and would be subject to all other regulations.

– Multiple ADU’s for multifamily complexes do not qualify for the County Fee Wavier Program.

Detached ADUs in San Diego can have a maximum size of 1,200 sq. ft. regardless of the size of the primary dwelling.

In San Diego County, attached accessory dwelling units shall conform to the height limits of the zone, except that an accessory dwelling unit 16 feet in height shall be allowed regardless of the applicable height limit.

In San Diego County, a detached ADU is limited to 25 feet in height.

Consistency in exterior features, including roofing, trim, walls, windows, and color palette, between the ADU and the primary dwelling unit is required.

For all newly constructed detached ADUs, the following guidelines must be observed:

* A minimum of 4 ft. setbacks from the property line in the front yard, side yard, and rear yard is required.

* On corner lots, exterior side yard setbacks of at least 4 ft. from the edge of the easement, street, or property line are necessary.

* ADUs that are 800 sq. ft. or smaller may encroach into the front yard setbacks, but this allowance is subject to the discretion of the County. Zero lot lines will not be allowed if there is available space to move back from the property line.

No setbacks are required if an existing and permitted accessory structure or a portion thereof is being converted into an ADU, except for fire safety.

ADUs constructed above garages and two-story ADUs must maintain side and rear setbacks of 5 ft. Furthermore, existing backyard and side yard structures should maintain distances of 6 ft. between them and 4 ft. from eave to eave.