Mendocino County, CA Accessory Structures: Garage Conversions (2026)

Mendocino County does not publish a stand-alone garage-conversion ordinance; conversions are reviewed through the building-permit process and the applicable zoning chapter. Because the County follows California's ADU statutes (Gov. Code 66310-66342), converting an existing garage or other accessory structure into an Accessory Dwelling Unit is an allowed and relatively streamlined path. The County's ADU guidance recognizes conversion of existing space, and state law treats conversion of existing structure to an ADU favorably (for example, no additional setback is required for an ADU created within an existing structure, and conversion ADUs are reviewed ministerially). A garage converted to habitable space must meet building-code requirements for light, ventilation, ceiling height, egress, fire separation and energy standards, which is why a building permit is required even though the footprint does not change. Removing required covered parking can trigger parking-replacement questions, though state ADU law waives replacement parking when a garage is converted into an ADU. In the unincorporated Coastal Zone, a garage conversion that changes the use or intensity of development may also require a Coastal Development Permit under the Coastal Zoning Code (including Chapter 20.458 for ADUs). Always verify whether your parcel is inland or coastal and confirm requirements with Planning & Building Services before starting work.