Rancho Cucamonga, CA Accessory Structures: ADU Rules (2026)

Rancho Cucamonga complies with California Government Code 65852.2 and 65852.22, which mandate that all cities allow Accessory Dwelling Units (ADUs) and Junior ADUs (JADUs) in residential zones. On single-family lots, owners may build one detached ADU up to 1,200 square feet, one attached ADU up to 50 percent of primary dwelling size or 1,000 square feet (whichever is greater), plus one JADU up to 500 square feet carved from the primary dwelling. Multi-family properties can convert non-livable space (storage, attics, garages) to up to 25 percent of existing units as ADUs, plus up to two detached ADUs. The state preempts the citys setbacks to 4 feet side and rear, and up to 16 feet height is allowed by right (with some exceptions for 18 to 25 feet near transit and for two-story ADUs). Parking is generally not required if the ADU is within half a mile of transit or in a historic district. Owner-occupancy of the primary dwelling is no longer required for ADUs permitted between 2020 and 2025 under state law. Rancho Cucamonga submits its ADU ordinance to HCD for review, and the city offers preapproved plans to speed permitting. School fees, development impact fees, and utility connection fees are limited by state law for ADUs under 750 square feet.