ADU Regulations in Fairfield, California
Solano County · CA · Pop. 120,000
Max ADU Size
1,200
sq ft detached
Rear Setback
4 ft
Permit Timeline
60 days
Build Cost
$145,000 – $295,000
Zoning
Allowed ADU Types
ADUs and JADUs permitted by right on any residentially zoned lot with an existing or proposed dwelling unit. State law preempts any local owner-occupancy conditions.
Source: City of Fairfield — Accessory Dwelling Units · Fairfield Municipal Code Title 25 (Zoning Ordinance)
Dimensions
Size & Setback Requirements
Detached
1,200
sq ft max
JADU
500
sq ft max
Attached
50% of primary home, max 1,200 sq ft
Setbacks
front
Same as primary dwelling per underlying zone
side
4 ft
rear
4 ft
Max height: 16 ft
Lot coverage: Per underlying zone
Garage conversions and existing structure conversions may maintain existing (non-conforming) setbacks. Standard 800 sq ft ADU allowed regardless of lot coverage on most residential lots.
Permitting
Permit Process
Department
City of Fairfield — Community Development Department, Planning Division
Review Timeline
60 days
Permit Fees
$5,500 – $11,000
Impact Fees
Impact fees waived for ADUs under 750 sq ft; prorated for larger units
Required Documents
- ›Site plan with property dimensions and setbacks
- ›Floor plans
- ›Elevations
- ›Title 24 energy compliance report
- ›Structural drawings
- ›Grading and drainage plan (if applicable)
Fairfield's location along the I-80 corridor between Sacramento and the Bay Area attracts commuter renters. Travis AFB generates consistent military family rental demand, supporting strong ADU occupancy rates.
Visit City of Fairfield — Community Development Department, Planning Division →Infrastructure
Utilities & Requirements
Solar
Required
Parking
Not required
Separate Meter
Optional
Fire Sprinklers
See note
Financials
ADU Costs in Fairfield
Typical Build Cost
$145,000 – $295,000
Cost per Sq Ft
$200 – $265
Monthly Rental
$1,400 – $2,200/mo/mo
Property Value Added
Adds $110,000 – $200,000 to property value
Available Grants & Programs
- ★CalHFA ADU Grant Program available (up to $40,000)
Travis AFB proximity creates consistent military rental demand. The I-80 corridor location attracts Bay Area and Sacramento commuters. Below-median construction costs make Fairfield a relatively affordable ADU market in the greater Bay Area region.
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Fairfield Quick Facts
- Max size1,200 sq ft
- Rear setback4 ft
- Permit timeline60 days
- Build cost$145,000 – $295,000
- Rental income$1,400 – $2,200/mo/mo
- Owner occupancyNot required
Official Source
City of Fairfield — Accessory Dwelling UnitsFairfield Municipal Code Title 25 (Zoning Ordinance)
Last verified: March 14, 2026
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ADU rules change often.
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