Antioch, CA Accessory Structures: Tiny Homes (2026)

Antioch Municipal Code 9-5.3805 (Accessory Dwelling Units), adopted by Ordinance No. 2121-C-S, defines an ADU to include both manufactured homes (as defined in California Health & Safety Code section 18007) and efficiency units (as defined in California Health & Safety Code section 17958.1). That definition makes Antioch's ADU pathway the primary way to permit a tiny home as a permanent residence. Detached new-construction ADUs may not exceed 1,200 square feet of floor area, with a 16-foot height cap for one-story detached units and Cal. Gov. Code 65852.2 state-allowed exceptions for ADUs above garages or near transit. A Junior ADU must be no larger than 500 square feet and contained within the walls of an existing or proposed single-family home, and a JADU triggers an owner-occupancy requirement (the owner must live in either the JADU or the main house). Standard ADUs do not carry an owner-occupancy requirement. Side and rear setbacks for an ADU are a minimum of 4 feet, and replacement parking is not required when an ADU is converted from an existing garage or accessory structure. Tiny homes on wheels (THOWs) and park-model RVs are not accepted as ADUs because they are not built to the California Residential Code on a permanent foundation; California Health & Safety Code section 18028 sets a separate framework that defines a tiny house on wheels as a recreational vehicle, not a dwelling, when used outside a permitted RV or mobilehome park. Antioch also recognizes Cottage Communities (clusters of three or more cottages designed as a coherent small community) as a separate code concept that allows compact small-footprint homes through a planned-development pathway. A building permit, electrical permit, and connection to city water and sewer are required before occupancy.