ADU rules in Sonoma, CA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Sonoma allows ADUs and JADUs in all residential zones (R-HS, R-R, R-L, R-S, R-M, R-H, R-O, R-P) under SMC Chapter 19.45, consistent with Cal. Gov. Code 65852.2. Detached ADUs are capped at 850 sq ft (or up to 1,200 sq ft with proportional limits) with a 4-foot side/rear setback and 16-foot height for single story.
SMC 19.45.040 sets the citywide ADU development standards. Single-story detached ADUs may not exceed 16 feet measured to the peak; two-story detached ADUs may not exceed 25 feet. Minimum side and rear setbacks are 4 feet for both attached and detached ADUs. Where a zone's regular front or street-side setback would block an 800 sq ft ADU, the setback is reduced to a minimum of 4 feet, per state law floor. Attached ADUs are capped at 150 sq ft minimum, max 30% of the primary dwelling's living area. Detached ADUs run 150-850 sq ft (state floor protects up to 800-1,200 sq ft depending on bedrooms). JADUs (junior ADUs) are limited to 500 sq ft and must be carved out of an existing single-family home (SMC 19.45.030). Fire sprinklers in the ADU are only required if the primary dwelling has sprinklers; construction of the ADU does not retroactively trigger sprinklers in the existing home (SMC 19.45.040; Permit Sonoma Fire Prevention guidance).
Per SMC 19.45.090, violations of Chapter 19.45 are unlawful and subject to the enforcement penalties and procedures of SMC Chapter 1.28 (general administrative citation/abatement). The city may also pursue any other legal remedies against the owner of an unpermitted or non-compliant ADU/JADU. Unpermitted ADUs typically must be brought into compliance, legalized, or removed.
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