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

Glenn County Code Title 15 defines a 'private garage' as a detached accessory building or portion of a main building used for parking or temporary storage of the occupants' vehicles. Converting that space into independent living quarters changes its use. If the conversion creates a separate dwelling, it is a 'second dwelling' permitted under Chapter 15.175 and must satisfy the Minimum Residential Construction Standards of Chapter 15.590 - including a permanent foundation and a separate entrance under Section 15.590.020(B) - and is approved by the Planning Director once it meets all standards. A conversion that simply adds habitable rooms to the existing single-family residence (not a separate unit) still requires a building permit and must comply with the underlying zoning district's setback, height and lot-coverage rules and the building codes adopted by the county. The Title 15 text dates to 2018 and references former Government Code Section 65852.2; current state ADU law in Government Code Sections 66310-66342 controls and requires the county to approve a qualifying garage-to-ADU conversion ministerially. Under that state law the conversion of an existing legal structure is generally exempt from minimum setbacks, and replacement parking cannot be required when a garage or covered parking is converted to an ADU. Confirm the applicable pathway with Glenn County Planning before starting work.