ADU Rules: Petaluma vs Sonoma
How do adu rules rules compare between Petaluma, CA and Sonoma, CA?
Petaluma has fewer restrictions than Sonoma.
Petaluma, CA
Sonoma County
Petaluma IZO §7.030 implements California's permissive ADU laws (Gov Code §65852.2). Most single-family lots may build at least one ADU and one Junior ADU.
View full Petaluma rules →Sonoma, CA
Sonoma County
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.
View full Sonoma rules →Key Facts Comparison
| Fact | Petaluma | Sonoma |
|---|---|---|
| Detached ADU Max | 800 sq ft (statewide standard) | - |
| Setback | 4 ft side/rear | - |
| Approval Window | 60 days | - |
| Code chapter | - | SMC Ch. 19.45 |
| Max detached ADU size | - | 850 sq ft (state floor: 800-1,200) |
| Min side/rear setback | - | 4 feet |
| Max height (1-story detached) | - | 16 feet to peak |
| JADU max size | - | 500 sq ft (within existing home) |
| Allowed zones | - | R-HS, R-R, R-L, R-S, R-M, R-H, R-O, R-P |
Highlighted rows indicate differences between cities.
Petaluma FAQ
Do I need to live in the main house?
Owner-occupancy requirements have been suspended statewide through Jan 1, 2025 (now extended).
Sonoma FAQ
Can I build an ADU on any residential lot in Sonoma?
Yes. SMC 19.45 permits ADUs in all eight residential zoning districts (R-HS through R-P), so long as the lot already contains or is proposed to contain a single-family or multifamily dwelling.
Do I need fire sprinklers in a new ADU?
Only if the primary dwelling already has sprinklers. Per SMC 19.45.040 and Permit Sonoma Fire Prevention guidance, building an ADU does not retroactively force sprinklers into the existing main house, and ADUs 1,200 sq ft or less may apply for mitigation in WUI areas.
What's the difference between an ADU and a JADU here?
An ADU is a separate independent unit up to 850 sq ft (detached) on the same lot. A JADU is a smaller unit (max 500 sq ft) carved out of the existing single-family home, sharing some facilities, and is subject to an owner-occupancy requirement under SMC 19.45.030.
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