Accessory Structures in Ontario, CA (2026)
5 verified accessory structures rules for Ontario, California, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Ontario must allow ADUs and JADUs under California Gov Code 65852.2 and 65852.22 on all single-family and most multifamily lots. Approval is ministerial within 60 days, with no minimum lot size.
Ontario ADU Rules
Some RestrictionsShed Rules
Ontario follows CRC Section R105.2, exempting one-story detached sheds under 120 sq ft from a building permit. Sheds must still meet zoning setbacks, height limits, and trade permits for electrical.
Ontario Shed and Accessory Building Rules
Few RestrictionsGarage Conversions
Ontario allows garage-to-ADU conversions under Gov Code 65852.2 with no replacement parking required. Non-ADU conversions to living space still need a building permit and must replace covered parking.
Ontario Garage Conversion Rules
Some RestrictionsCarport Rules
Ontario allows carports on residential lots subject to zoning setbacks and a building permit for any carport 200 sq ft or larger. Properly sized carports count toward required covered parking.
Ontario Carport Rules
Some RestrictionsTiny Homes
Foundation-built tiny homes qualify as ADUs under Gov Code 65852.2 in Ontario. Tiny homes on wheels are treated as RVs or park trailers and cannot be used as permanent dwellings on residential lots.
Ontario Tiny Home Rules
Heavy RestrictionsLooking for San Bernardino County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Ontario city rules.
Accessory Structures in San Bernardino County →