Ontario, CA Accessory Structures: ADU Rules (2026)

California Government Code 65852.2 (ADU statute) and 65852.22 (Junior ADU statute), as amended by a long list of AB and SB bills (AB 881, SB 9, AB 2221, AB 976, AB 1033 among others), require the City of Ontario to ministerially approve one ADU plus one JADU on any single-family lot, and at least one detached ADU per multifamily parcel with interior conversions allowed on top. Ontario has adopted a local ADU ordinance consistent with state law. Maximum size limits are at least 850 square feet for a one-bedroom detached ADU and 1,000 square feet for two bedrooms or more, with four-foot side and rear setbacks and no minimum lot size. Parking cannot be required within a half mile of transit or in a historic district, and replacement parking cannot be required when a garage is converted. Owner-occupancy cannot be required for ADUs permitted between January 1, 2020 and January 1, 2025 under AB 881, with recent extensions. Ontario Planning must approve a compliant application ministerially within 60 days. Impact fees are capped by AB 1600 for units under 750 square feet (fee cannot be charged).