Newport Beach, CA Accessory Structures: ADU Rules (2026)

" One ADU is allowed internal to a dwelling, one attached new-construction ADU, and one detached new-construction ADU per single-unit lot (up to two detached ADUs on a multi-unit lot); conversions of existing multi-unit buildings can add ADUs up to 25 percent of the existing unit count. A separate junior ADU (up to 500 square feet) is allowed on single-unit lots, attached to or within the existing dwelling, with independent exterior access. Detached ADUs are capped at 16 feet in height, rising to 18 feet on a lot with an existing multi-unit, multi-story dwelling or within one-half mile of a major transit stop, and two stories over a detached garage if it meets underlying-district height and setback rules.

Size is capped at 850 square feet for a studio or one-bedroom unit and 1,000 square feet for two or more bedrooms, though a conversion of existing space is exempt from that cap and other development standards cannot squeeze a new ADU below 800 square feet. Attached and detached ADUs need only a 4-foot side and rear setback (less if the underlying district allows less), and no additional setback applies when converting or replacing an existing garage or carport in its footprint. Parking is capped at one space per ADU and waived entirely near transit, car-share vehicles, or when converting existing space, and no fire sprinklers or passageway are required.

ADUs cannot be sold separately from the primary lot and cannot be rented for 30 days or less; junior ADU owners must record a deed restriction with the County Recorder covering owner-occupancy, no separate conveyance, and short-term rental limits.