Fontana, CA Accessory Structures: ADU Rules (2026)

Accessory Dwelling Units in Fontana are governed primarily by California Government Code 65852.2 and 65852.22, which preempt most restrictive local rules. Fontana has adopted an ADU ordinance in Municipal Code Title 30 (Zoning) that follows the state framework. Any single-family lot may have one ADU and one JADU, and multi-family lots may convert existing non-livable space and add up to two detached ADUs. Maximum size for a detached ADU is 1,200 square feet or 1,000 square feet depending on bedroom count per state law; attached ADUs are capped at 50 percent of the primary dwelling floor area or 1,200 square feet, whichever is less. Fontana must ministerially approve complete applications within 60 days and cannot require replacement parking when a garage is converted, or any parking at all within one-half mile of high-quality transit. Setbacks are limited to 4 feet from side and rear lot lines for new detached ADUs, and no setbacks are required for ADUs built within existing structures. Owner-occupancy cannot be required for ADUs permitted between 2020 and 2024; JADUs always require owner-occupancy. School impact fees apply only to ADUs 750 square feet or larger. Fontana charges plan check and building permit fees, and utility connection fees are waived for ADUs under 750 square feet. Short-term rental of an ADU is not allowed because Fontana prohibits STRs citywide.