Rancho Cucamonga, CA Accessory Structures: Garage Conversions (2026)

Converting an attached or detached garage to a conditioned ADU in Rancho Cucamonga is one of the most popular accessory dwelling unit paths because state law expressly protects it. Under Government Code 65852.2, cities cannot require replacement parking when a garage is converted to an ADU, and ministerial approval is required within 60 days. The garage must be permitted under the California Residential Code as a conditioned living space, which means insulation to current Title 24 energy standards, egress windows in sleeping rooms (minimum 5.7 square feet openable area), smoke and CO detectors, proper ceiling height (typically 7 feet minimum), a kitchen or kitchenette, bathroom with shower, HVAC, and weather-tight construction. The existing garage door typically must be removed and replaced with a fully framed, insulated wall or doorway. Plumbing and electrical permits are required in addition to the Building permit. Rancho Cucamonga charges reduced or waived development impact fees for ADUs under 750 square feet. HOAs cannot prohibit garage-to-ADU conversions but may regulate exterior appearance. The converted garage cannot be rented as a short-term rental (under 30 days). Garage conversions retain the original garage setback, which may be closer to the property line than typical ADUs are allowed.