Accessory Structures in Contra Costa County, CA (2026)

Contra Costa County Ordinance Code § 82-24.008

One accessory dwelling unit may be located on any lot in a single-family residential district (R-6, R-7, R-10, R-12, R-15, R-20, R-40, R-65, and R-100), planned unit district (P-1) for residential uses, or a multiple-family residential district (M-6, M-9, M-12, M-17, and M-29).

Contra Costa County Ordinance Code § 82-24.014(a)-(c) (Occupancy and sale restrictions)

(a)No accessory dwelling unit or junior accessory dwelling unit may be rented or offered for rent for a term of less than thirty days.(b)A junior accessory dwelling unit may not be sold separately from the primary single-family dwelling.(c)An accessory dwelling unit may not be sold separately, except in conformance with Government Code section 66341.

Contra Costa County Ordinance Code § 72-6.202

Per Contra Costa County Ordinance 72-6.202: No person, firm, or corporation shall erect, construct, enlarge, alter, repair, move, improve, remove, convert or demolish any building or structure regulated by this title... without first obtaining the necessary permits from the county building official. According to the 2022 California Residential Code (CRC), permits shall not be required for the f...

Contra Costa County Ordinance Code Chapter 82-24

If an accessory dwelling unit is attached to a primary residence, the accessory dwelling unit must be an internal conversion of a garage or other area within the existing primary residence, or an addition to the existing primary residence. A setback is not required for an existing garage that is converted to an accessory dwelling unit.