ADU, Granny Flat & Mother-in-Law Suite Contractors in San Diego

Most single-family lots in San Diego qualify for at least one ADU (granny flat) under California state law. The main requirements are: the lot must be zoned residential, the primary structure must already exist, and the ADU must meet minimum setbacks (4 feet from rear and side property lines for detached ADUs). Coastal overlay zones in La Jolla, Del Mar, and Encinitas have additional permit requirements. We assess your specific parcel during the free consultation to confirm what's allowable.

A granny flat (detached ADU) is a completely separate structure on your lot with its own foundation, utilities, and outdoor space. A mother-in-law suite is an attached addition to the primary home — it shares a wall with the main house but has a private entrance, bedroom, bathroom, and kitchenette. Granny flats offer more separation and are preferred for rental use; mother-in-law suites are more cost-effective and suited for multigenerational living.

A detached granny flat (ADU) in San Diego typically costs $150,000 to $250,000 for a 400–600 sq ft unit. Larger or more premium units can reach $300,000+. Key cost factors include size, utility connection requirements, site access, and finish level. Garage conversions start lower ($120,000–$180,000) because no new foundation is required. We provide a fixed-price proposal after a site assessment — no open-ended estimates.

Our Price Lock Guarantee means your proposal price is locked to the signed scope of work. The only thing that changes the price is a written change order that you initiate and approve. For ADUs, we complete thorough site assessment and utility evaluation before pricing so the proposal is accurate.

ADU construction in San Diego ranges from $120,000 for a garage conversion to $350,000+ for a large detached ADU with high-end finishes. Detached ADUs typically cost $180,000–$300,000. Key cost factors include size, utility connection requirements, site access, and finish level.

Construction takes 3 to 5 months depending on ADU type and complexity. Design and permitting add 2 to 4 months before that — the City of San Diego is required to process ADU permits within 60 days, though plan for 60–90 days in practice. Total project timeline from kickoff to move-in is typically 5 to 9 months.

No. California state law (AB 3182) eliminated the owner-occupancy requirement for ADUs. You are not required to live in the primary home or the ADU. You can build, rent both units, and be off-site.

It depends on your goals. Garage conversions are less expensive ($120K–$180K) and faster to permit because no new foundation is required, but they sacrifice parking and tend to be smaller. Detached ADUs cost more ($180K–$350K) but offer complete separation, more design flexibility, and are typically more attractive to renters and appraisers.

California state law sets a 4-foot minimum side and rear setback for new detached ADUs — San Diego cannot require more. Maximum size is 1,200 sq ft for a detached ADU under state law. Junior ADUs (JADUs) within the existing home can be up to 500 sq ft. Height limits are typically 16 feet (18 feet within half a mile of transit). Coastal overlay zones in La Jolla, Del Mar, and Encinitas have additional review requirements.