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

Alpine County (entirely unincorporated) processes garage conversions as accessory dwelling units under California ADU law because Chapter 18.69 does not comply with current state law. The county's ADU Information Sheet states that if an ADU involves conversion of an existing structure such as a garage, or a portion of the existing primary dwelling, there is no maximum size requirement. Likewise, no setback is required for an existing living area or existing accessory structure converted to an accessory dwelling or to a portion of one. Junior ADUs, by contrast, must stay within the existing single-family dwelling and may not be detached. A building permit is still required from the Building Safety Division, with a project description, verification of an adequate well or community water supply, and verification that the onsite or community wastewater system has adequate capacity. Parking removed to create the converted ADU does not have to be replaced, and parking standards do not apply in the Markleeville Historic District. Zoning Chapter 18.68 also allows garages and other accessory buildings to be attached to the main building by a common wall or connected by a breezeway (Section 18.68.140.C), which is relevant where a converted garage adjoins the home.