Accessory Structures in Fairfield, CA: What Residents Actually Need to Know

If you live in Fairfield or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Fairfield has 5 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

ADU Impact Fees

Fairfield charges accessory dwelling units and junior ADUs a water connection fee sized to their fixture-unit burden under City Code Section 22.20.060(C). Section 22.20.070(B) waives that charge entirely for any ADU or JADU under 750 square feet, or one that meets Government Code Section 66323(a)(1).

Key details: Fee basis: proportional to fixture-unit burden. Exemption 1: ADU/JADU under 750 sq ft. Exemption 2: meets Gov. Code § 66323(a)(1). New house + ADU together: full connection charge applies. Fee adjusts: annually each April 1.

Nonpayment does not draw a citation, it blocks the project: Section 22.20.040 bars any water or sewer connection, and bars meter installation, until the connection charge is paid, so an unpaid ADU fee stalls final building sign-off. Where a fee dispute or reallocation is needed, owners work directly with the FMU director, who has discretion under Section 22.20.030 to determine capacity reallocation between parcels.

Shed & Carport Rules

Fairfield's Zoning Ordinance sorts backyard sheds into a small accessory structure class capped at 7 feet high and 60 square feet, screened behind a solid 6-foot fence, or a large accessory structure class up to 16 feet with no size limit but confined to the rear half of the lot.

Key details: Small accessory structure max height: 7 feet. Small accessory structure max size: 60 sq ft. Large accessory structure max height: 16 feet (up to 35 ft, note 1). Rear-yard coverage, large structure: 20% (30% combined, note 4). Governing section: § 25.20.4.1, Table 25-7.

A shed or accessory structure built beyond the height, size, or setback limits in Table 25-7 without approval is a zoning violation; the Community Development Department can deny the building permit, require removal or reconstruction to conform, or issue an administrative citation under Chapter 1, Article I of the City Code for unpermitted work.

Garage Conversions

Fairfield bars garage conversions on lots under 4,500 square feet and requires a replacement on-site parking space for any converted space that displaces required parking. The garage door itself must stay intact or be redesigned to architecturally match the house.

Key details: Minimum lot size for conversion: 4,500 sq ft. Replacement parking: 1 space per space displaced. ADU/JADU conversions: exempt from parking replacement. Planter depth (door-removal option): 30 inches. Governing section: § 25.20.4.3.

A garage conversion completed without demonstrating Zoning Ordinance compliance, without the required replacement parking space, or without one of the three approved door treatments is subject to permit denial, required remediation, or an administrative citation from the Community Development Department under Chapter 1, Article I.

ADU Rules

Fairfield's zoning code caps a detached ADU at 1,200 square feet and 16 feet in height, with four-foot side and rear setbacks, under § 25.20.4.11. An attached ADU can't exceed 50 percent of the primary home's floor area or 1,200 square feet, whichever is smaller.

Key details: Detached ADU max size: 1,200 square feet. Attached ADU max size: 50% of primary home or 1,200 sq ft. Max height: 16 feet (25 feet over garage). Side/rear setback: 4 feet for new construction. Parking: No additional parking required.

Building an ADU larger than the code's size or height caps, or without required setbacks or the Planning ADU/building permits, exposes the property to a stop-work order and code enforcement action from Fairfield's Building Division, and the unit can't legally receive a certificate of occupancy. The code also bars issuing a certificate of occupancy for an ADU or JADU before the primary dwelling has one, and prohibits selling an ADU or JADU separately from the main house.

ADU Owner Occupancy

Fairfield requires the property owner to live on-site, in either the primary home or the new unit, whenever a junior accessory dwelling unit (JADU) is added, under Fairfield Municipal Code § 25.20.4.11.G. Detached ADUs built alone carry no such owner-occupancy requirement.

Key details: Trigger: Any property with a JADU. Owner may live in: Primary residence or the JADU. Exempt owners: Government agency, land trust, housing organization. Enforcement tool: Recorded deed restriction runs with land. JADU size cap: 220 to 500 square feet.

Renting out both the primary residence and the JADU with no owner living on-site breaches the deed restriction recorded under § 25.20.4.11.H and the owner-occupancy requirement in § 25.20.4.11.G, and can subject the property to code enforcement action by the City and potential legal action to enforce the recorded deed restriction against the property owner.

The Bottom Line

Fairfield's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Fairfield is broadly strict or permissive.

This guide is based on Fairfield's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.