ADU Rules in Solano County, California
We track 3 cities in Solano County. Each city writes its own ADU ordinance on top of California law, so size limits, fees, and design rules differ from one city to the next. Among the cities we track, Fairfield has the lowest starting permit fees ($5,500 – $11,000).
Cities
3
Max Detached Size
1,200 sq ft
Build Costs From
$140,000
Pre-approved Plans
1 of 3 cities
Solano County Cities Compared
| City | Max detached | Height | Permit fees | Build cost |
|---|---|---|---|---|
| Vallejo | 1,200 sq ft | 16 ft | $6,000 – $12,000 | $155,000 – $310,000 |
| Fairfield | 1,200 sq ft | 16 ft | $5,500 – $11,000 | $145,000 – $295,000 |
| Vacaville | 1,200 sq ft | 16 ft (detached, single-family lot) | $5,500 – $11,000 | $140,000 – $285,000 |
Vallejo ADU rules
Vallejo allows ADUs up to 1,200 sq ft, and new units need a bathroom, full kitchen and their own entrance. Detached ADUs over 850 sq ft on lots under 10,000 sq ft must meet lot coverage limits. Ferry access to San Francisco has pushed up interest in ADUs in recent years.
Fairfield ADU rules
Fairfield's ADU information is run through the city's Housing Services department, which publishes a quick guide to ADUs. Rental demand is shaped by Travis Air Force Base and commuters on the I-80 corridor between Sacramento and the Bay Area. Conversions of garages and other existing structures can keep their existing setbacks.
Vacaville ADU rules
Vacaville has four city pre-approved ADU plans, from a 375 sq ft studio to a 908 sq ft two-bedroom, and applications using them get a decision within 30 days of being deemed complete. Detached ADUs can be up to 1,200 sq ft. Travis Air Force Base keeps rental demand steady.
Rules that apply in every California city are summarized in our California ADU law guide. See all California cities or compare every city side by side.