Orange County, CA Accessory Structures: Garage Conversions (2026)

Orange County regulates ADU and JADU conversions in Section 7-9-90 of the Codified Ordinances (Title 7, Land Use and Building Regulations - Division 9, Article 2, the Comprehensive Zoning Code), implementing California Government Code Sections 65852.2 (ADUs) and 65852.22 (JADUs). On a building site with an existing or proposed single-family dwelling, Section 7-9-90(a)(2) allows a property owner to establish one ADU within a converted existing accessory structure on a ministerial basis; the converted ADU may not exceed the square footage of the converted structure, up to a maximum of 1,200 square feet. Section 7-9-90(c)(1) further allows an expansion of up to 150 square feet beyond the existing physical dimensions of the primary dwelling or converted accessory structure to accommodate ingress/egress, with that expansion counted toward the unit's maximum allowable size. A junior ADU under Section 7-9-90(a)(3) is converted from space within the primary dwelling (or a portion of an existing ADU), is capped at 500 square feet, and requires the building site's owner to occupy a dwelling unit on the site, consistent with Government Code Section 65852.22. On parking, Section 7-9-90(d)(3) provides that no replacement of removed parking spaces is required when an existing garage, carport, or covered parking garage is converted to an ADU or removed to accommodate ADU construction - a permissive rule that mirrors state law and removes the chief obstacle to garage conversions. Section 7-9-90(d)(4) waives any new parking requirement for the ADU itself in several circumstances, including when the ADU is attached to or contained within the existing primary residence or an existing accessory structure, when the unit is within a one-half mile walk of public transit, or when the unit has no bedrooms. Section 7-9-90(c)(2) requires the ADU to comply with all applicable building codes, which in unincorporated Orange County means the California Building Standards Code (Title 24) as adopted under Title 7 of the Codified Ordinances - converted garage walls, floors, ceilings, electrical, plumbing, and egress windows must be brought up to habitable-space standards. Section 7-9-90(c)(5) prohibits the ADU from being sold separate from the primary dwelling and prohibits short-term rentals (less than 30 days) of any ADU or JADU. Section 7-9-90(c)(7) waives any new or separate utility connection or related capacity charge if the ADU is attached to or contained within the space of an existing primary dwelling or accessory structure. The county processes ADUs ministerially: under Government Code Section 65852.2, an Orange County application for a garage-conversion ADU must be approved or denied within 60 days. Permits are issued through OC Public Works Development Services. Section 7-9-90 only applies in unincorporated areas; the 34 incorporated cities in Orange County (including Anaheim, Santa Ana, Irvine, Huntington Beach, Garden Grove, Orange, Fullerton, Costa Mesa, Mission Viejo, Westminster, Newport Beach, Buena Park, Lake Forest, Tustin, Yorba Linda, San Clemente) maintain their own ADU ordinances which must comply with the same state law but may differ on detached new-construction ADU standards.