State law permits ADUs up to 1,200 sqft for detached units. 6,000–8,000 sqft for standard residential neighborhoods. Some hillside and estate properties offer larger parcels. No minimum lot size required by state law to build an ADU.
Up to 18 feet for detached ADUs per 2025 regulatory updates. Up to 25 feet for attached ADUs in some qualifying residential zones.
4-foot minimum from rear and side property lines for new detached ADUs. Conversions of existing structures are exempt from setback requirements.
One parking space per ADU may be required. Exempt if within 0.5 miles of public transit, within one block of a car-share vehicle, or if the ADU is a conversion of existing space.
No owner-occupancy requirement for ADUs (made permanent by AB 976 in 2025).
Estimated cost $250K–$400K. Permit fees Contact city (updated July 2025). Impact fees: Waived under 750 sqft.
Brea is an affluent, family-friendly community of approximately 48,000 residents in north Orange County, with a median household income of $131,000. Known for its excellent schools (Brea-Olinda Unified School District), well-maintained neighborhoods, and the Brea Mall — one of the region's premier shopping destinations — Brea offers a high quality of life that attracts long-term residents. The city sits along the 57 freeway corridor near the Birch Hills Golf Course and Carbon Canyon Regional Park, providing quick access to both Orange County and Inland Empire employment centers. Brea has proactively embraced ADU development by offering a pre-approved ADU plans program that streamlines permitting and reduces costs for homeowners.