Sonoma, CA Accessory Structures: Garage Conversions (2026)

SMC Chapter 19.45 implements California's ADU statutes (Gov. Code §§66310–66342) for the City of Sonoma. Per SMC 19.45.040, an ADU may be created by converting all or part of an existing garage, accessory structure, or portion of the primary dwelling. Converted ADUs on a single-family lot are not required to install a new or separate utility connection between the ADU and the utility main. A converted-garage ADU keeps the existing setbacks of the legal structure; a new detached ADU built in the garage footprint must observe a 4-ft side and rear setback. Maximum unit size is 850 sq ft for a studio or one-bedroom and 1,000 sq ft for a two-bedroom. Detached single-story ADUs may not exceed 16 ft, and two-story detached ADUs may not exceed 25 ft. Off-street parking for the ADU is required (one space), but the requirement is waived when the ADU is part of the existing primary dwelling or existing accessory structure (which covers most garage conversions), within ½ mile of a public transit stop, or within an architecturally designated historic district — Sonoma's downtown is largely covered. No replacement parking is required for the primary dwelling when its garage is converted.