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

Mariposa County defers to State ADU Law (Gov. Code 66310-66342) for second units, which is the typical pathway for a garage-to-living-space conversion. Under Gov. Code 66323(a)(1), one ADU per lot is permitted within the converted space of an existing single-family dwelling or accessory structure (such as a garage). State law provides that 'No setback shall be required for an ADU or JADU created within an existing living area or accessory structure' (Gov. Code 66314(d)(7)). A converted ADU made from an accessory structure is also eligible for up to a 150-square-foot expansion solely to accommodate ingress and egress. Alternatively, a garage may be converted to a Junior ADU (JADU) of no more than 500 sq ft contained within the single-family residence; note that for JADU purposes an attached garage is treated as part of the single-family dwelling (Gov. Code 66333(d)). If a JADU shares sanitation facilities with the main home, owner-occupancy is required (Gov. Code 66333(b)). Any conversion still must meet the California Building Standards Code (Title 24) for habitable space, and you must apply through the County's permitting system. Replacing required off-street parking lost to the conversion may be addressed under the County's parking rules.