Top-rated Saddleback Valley Unified schools drive consistent family demand, Lake Mission Viejo and recreational amenities make the city highly desirable, consistent lot sizes of 5,000–8,000 sqft are well-suited for detached ADUs, and strong rental demand from hospital workers, college staff, and families priced out of purchasing in the area.
Mission Viejo is one of the largest master-planned communities in the United States, home to approximately 96,000 residents across a carefully designed landscape of residential villages, parks, and community amenities. The crown jewel is Lake Mission Viejo, a private 124-acre recreational lake available exclusively to residents, offering swimming, fishing, boating, and summer concerts. The city consistently ranks among the safest in America and is served by the highly rated Saddleback Valley Unified School District, with schools like Mission Viejo High School and Trabuco Hills High School drawing families from across south Orange County. Neighborhoods range from the original 1970s developments around the lake — including the Villages of Mission Viejo and Casta del Sol active-adult community — to newer hillside communities near O'Neill Regional Park. The I-5 freeway bisects the city, providing direct commute access to Irvine, Laguna Niguel, and San Diego County. Major employers include Providence Mission Hospital, Saddleback College, and the retail corridor along Marguerite Parkway and La Paz Road.
Confirm your property's zoning on the city's GIS map. Most single-family residential zones allow ADUs by right. Additionally, contact your HOA (if applicable) to request their ADU architectural guidelines — they can require design review but cannot deny a compliant ADU.
Create architectural plans including site plan, floor plan, elevations, structural, mechanical, electrical, and plumbing. Mission Viejo's consistent lot sizes (5,000–8,000 sqft) often favor a 600–800 sqft detached unit positioned along the rear property line. Match the existing home's roofline and exterior materials for HOA compatibility.
Submit your complete plan set to the Community Development Department. Include Title 24 energy compliance documentation. Mission Viejo processes ADU applications ministerially — no public hearing or discretionary review is required.
The city reviews plans for compliance with building codes and ADU regulations. State law mandates a 60-day maximum review period for compliant ADU applications. If your HOA requires concurrent review, submit to both simultaneously to avoid delays.
Once permitted, begin construction with your licensed contractor. Schedule required inspections at each milestone — foundation, framing, rough mechanical/electrical/plumbing, insulation, and final. HOA may request a pre-construction meeting to confirm design compliance.
Request final inspection from the Building Division. Once passed, receive your Certificate of Occupancy. Your ADU is now legal to rent or occupy.