Accessory Structures in Antioch, CA (2026)
4 verified accessory structures rules for Antioch, California, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Antioch implements California state ADU law through Antioch Municipal Code Section 9-5.3805, allowing one ADU plus one JADU on single-family lots with a four-foot side and rear setback, a 16-foot height limit for detached ADUs, and ministerial 60-day approval.
Antioch ADU and JADU Rules (AMC 9-5.3805)
Some RestrictionsAntioch Municipal Code § 9-5.3805 (Accessory Dwelling Units)
An Accessory Dwelling Unit (ADU) means an attached or detached residential dwelling unit that provides complete independent living facilities for one or more persons and is either located on a lot with a proposed or existing primary residence, or located in the IH Overlay District. The minimum required setback for a new construction ADU on a single-family property is 4 feet from the rear and in...
ADU Impact Fees
Antioch charges development impact fees on accessory dwelling units, but caps them below the standard per-unit rate. An ADU under 750 square feet pays no DIF at all, and larger units pay a size-proportioned share of the multifamily or single-family rate, whichever is less.
Antioch ADU Impact Fee Discounts
Some RestrictionsAntioch Municipal Code § 9-3.60(D)
(D) Accessory dwelling units. DIFs shall be collected for accessory dwelling units as follows: (1) Accessory dwelling units on multifamily properties shall pay the lesser of the following: (a) The multifamily rate; (b) The product of the following formula: (Square feet of accessory dwelling unit / Average square feet of all existing multi-family dwelling units on...
Shed & Carport Rules
Antioch Municipal Code Section 9-5.603 caps accessory structures in residential districts at 15 feet tall, requires a five-foot rear and interior side setback, and exempts truly portable storage sheds (under 120 sq ft, under 8 ft tall, no foundation) from permit requirements.
Antioch Shed and Accessory Building Rules (AMC 9-5.603)
Some RestrictionsAntioch Municipal Code § 9-5.603 (Accessory Buildings)
In residential districts, the maximum allowable height is 15 feet for accessory structures. Detached accessory structures shall be located behind the required front yard setback and cover no more than 40% of the rear yard area required for the main building. The minimum side yard for accessory structures is 20 feet on corner lots and five feet on interior lots. A five-foot rear yard setback is ...
Garage Conversions
Antioch follows California state law allowing ministerial, by-right conversion of an existing garage into an ADU, with no setback added beyond fire-safety distance, no replacement parking required, and no fire-sprinkler requirement unless the primary dwelling already has sprinklers.
Antioch Garage-to-ADU Conversion Rules
Few RestrictionsCalifornia Government Code § 65852.2(a)(1)(D)(xi) and § 65852.2(b)(1)
(b)(1) When a local agency receives its first application on or after July 1, 2003, for a permit pursuant to this subdivision, the application shall be considered ministerially without discretionary review or a hearing... (a)(1)(D)(xi) When a garage, carport, or covered parking structure is demolished in conjunction with the construction of an accessory dwelling unit or converted to an accessor...
Looking for Contra Costa County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Antioch city rules.
Accessory Structures in Contra Costa County →