Fullerton, CA Accessory Structures: ADU Rules (2026)

Fullerton's ADU regulations conform to California's statewide ADU laws, which significantly limit local discretion over accessory dwelling unit approvals. Under Government Code Section 65852.2, Fullerton must ministerially approve (without discretionary review or public hearing) ADUs that meet objective standards. A single-family lot may have one ADU plus one JADU (a unit of 500 square feet or less created within the existing primary dwelling or attached garage). Detached ADUs may be up to 1,200 square feet for a two-bedroom unit (1,000 square feet for one bedroom, 850 square feet for studio). An 800-square-foot ADU with a height of 16 feet is automatically approved with a 4-foot rear and side setback regardless of other local standards. ADUs are exempt from minimum lot size requirements, lot coverage limits (for units up to 800 square feet), and floor area ratio calculations. No off-street parking is required for ADUs located within one-half mile of a public transit stop — given Fullerton's OCTA bus network and the Fullerton Transportation Center (Amtrak/Metrolink), many properties qualify. Impact fees are prohibited for ADUs under 750 square feet. Owner-occupancy requirements may not be imposed on ADUs (though JADUs require the property owner to occupy either the primary dwelling or the JADU). The city must approve or deny ADU applications within 60 days. Fullerton's Building Division processes ADU permits through the standard building permit process with plan check for building code compliance. Utility connection fees are capped and may not exceed the proportional share based on the ADU's square footage relative to the primary dwelling or a reasonable flat amount.