Fairfield, CA Accessory Structures: ADU Rules (2026)

Following Ordinance 2020-05 and 2021-14, Fairfield's ADU regulations conform to California Gov Code §65852.2 (ADU) and §65852.22 (JADU). ADUs and JADUs are permitted in all residential zones, including single-family, multi-family, and mixed-use districts. Both attached and detached ADUs are allowed. Size limits: detached ADUs up to 1,200 sq ft; attached ADUs not exceeding 50% of the primary dwelling's floor area or 1,200 sq ft, whichever is less; JADUs up to 500 sq ft and must be contained within the walls of an existing or proposed single-family dwelling. Maximum ADU height is 16 feet to the roof peak; when more than 50% of the gross floor area is located above an existing or proposed garage, the entire combined structure may reach 25 feet. Setbacks: no setback required for conversions of existing structures or rebuilds in the same footprint; 4 feet from side and rear lot lines for new construction; ADUs follow the zone's front-yard setback. ADUs cannot be sold separately from the primary residence unless Fairfield opts in to AB 1033, which it has not done as of mid-2026. JADUs require owner-occupancy of either the JADU or the primary dwelling. State law (SB 9) urban-lot-splits and duplexes may interact with ADU rights on eligible single-family lots.