Orange County, CA Accessory Structures: ADU Rules (2026)

Orange County implements California's state ADU mandate through Comprehensive Zoning Code Sec. 7-9-90, which expressly conforms to California Government Code Section 65852.2 (now recodified by the state as Gov. Code 66310-66342, effective Jan. 1, 2025). Because state law preempts local ADU restrictions, the County processes ADUs as ministerial (by-right) permits rather than discretionary approvals. On a single-family lot, an owner may build one ADU (attached or detached) plus one junior ADU (JADU). A newly built ADU within the buildable area may not exceed 1,200 sq ft; an attached ADU is capped at 50% of the primary dwelling's floor area, except the 50% limit cannot block at least an 800 sq ft unit. ADUs in side/rear setback areas are limited to 800 sq ft and 16 feet in height, kept at least 4 feet from side and rear property lines. JADUs must be converted from space within the primary dwelling and are capped at 500 sq ft. One parking space per ADU is required unless the unit is within a half-mile walk of transit, has no bedrooms, is within the primary residence, or other listed exceptions apply; JADUs need no parking. ADUs may be rented for 30+ days but not used as short-term rentals.