State law permits ADUs up to 1,200 sqft for detached units. 4,000–6,000 sqft typical residential lots — smaller than many south OC cities due to the planned community layout. Some detached single-family areas along Glenwood Drive and Canyon Wren reach 6,000–7,000 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, bonus rooms) are exempt from setback requirements.
One parking space per ADU may be required. Exempt if within 0.5 miles of public transit (OCTA bus routes along Aliso Creek Road and Pacific Park Drive), 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.
Aliso Viejo is one of California's newest incorporated cities, having become a municipality in 2001 after decades as a master-planned community developed by Mission Viejo Company. With approximately 51,000 residents, the city is characterized by its meticulously planned layout featuring newer infrastructure, underground utilities, and well-maintained common areas. The Aliso Viejo Town Center anchors the commercial district with restaurants, retail, and a movie theater, while Pacific Park — a 14-acre community sports complex — provides recreation for families. The city's housing stock was built primarily in the 1980s and 1990s, meaning electrical panels, sewer lines, and water mains are relatively modern compared to older Orange County cities — a significant advantage when connecting ADU utilities. Aliso Viejo sits along the Aliso Creek corridor with quick access to the SR-73 toll road and I-5 freeway, placing residents within 15 minutes of Laguna Beach, 10 minutes of Irvine Spectrum, and 20 minutes of John Wayne Airport. Major employers include Quest Software (now Dell), UST Global, and the retail and dining establishments along Town Center Drive.