State law permits ADUs up to 1,200 sqft for detached units. 5,000–8,000 sqft typical residential lots, with hillside parcels often 10,000+ sqft. No minimum lot size required by state law to build an ADU.
Up to 16 feet for single-story detached ADUs. Up to 25 feet for two-story ADUs per state law (AB 1332) in qualifying residential zones.
4-foot minimum from rear and side property lines for new detached ADUs. Conversions of existing structures (garages, workshops) 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 $5K–$12K. Impact fees: Waived under 750 sqft.
Rancho Santa Margarita is a master-planned community of approximately 50,000 residents nestled in the foothills of the Santa Ana Mountains in southeast Orange County. The city features a distinctly suburban character with well-maintained neighborhoods, tree-lined streets, and generous lot sizes ranging from 5,000 to 8,000 sqft — with hillside properties often exceeding 10,000 sqft. Bordered by O'Neill Regional Park and Tijeras Creek Trail, the community offers immediate access to hiking, mountain biking, and outdoor recreation that few OC cities can match. The family-oriented atmosphere, top-rated Capistrano Unified and Saddleback Valley Unified school districts, and proximity to major employers along the I-5 corridor make Rancho Santa Margarita a consistently desirable residential market.