Antioch, CA Accessory Structures: Garage Conversions (2026)

Garage conversions in Antioch are processed as Accessory Dwelling Units under Antioch Municipal Code Section 9-5.3805 and California Government Code Section 65852.2 (now codified at Government Code Sections 66310-66342 after SB 477 reorganization in 2024). The City confirms that conversion ADUs may be created from space on the lot of the primary residence, including "a master bedroom, attached garage, storage area, or similar use, or an accessory structure," and may also be built by tearing down a detached garage or shed and rebuilding it in the same location to the same dimensions. Conversions are exempt from the City's standard setback requirements provided the existing structure already complies, and from any replacement-parking requirement when a garage, carport, or covered parking structure is demolished or converted in conjunction with an ADU - this is required by state law. The conversion is exempt from off-street parking entirely if the property is within one-half mile walking distance of public transit. Fire-sprinkler retrofits cannot be required for an ADU if the primary residence does not have sprinklers. The City processes a complete ADU application ministerially within 60 days, and Pre-Approved ADU Plans are available through the Community Development Department. The converted space must meet the currently adopted California Residential Code for habitable space, including minimum ceiling height, light, ventilation, emergency egress, electrical service, plumbing, mechanical, insulation, and adequate fire-separation from any remaining attached portion of the primary dwelling.