The Casita WayDesign. Bid. Build.

Most San Diego County ADUs cost between $150,000 and $350,000 all-in. Garage conversions are the least expensive (often $150,000–$215,000), while a new detached 750 sq ft ADU with mid-range finishes typically runs $190,000–$250,000, plus roughly $10,000–$35,000 in permit, impact, school, and utility fees depending on your city and unit size. Casita's free online cost estimator gives you a live breakdown for your ADU type, size, finish level, and jurisdiction.

Plan on 9–13 months from first design meeting to move-in for a detached or attached ADU, and 6–10 months for a garage conversion. Design takes 4–8 weeks, city permitting 2–4 months (California requires cities to act on complete ADU applications within 60 days), and construction 4–6 months. Pre-approved plans can cut design and permitting time significantly.

Casita ADU is a construction management agency for accessory dwelling units — not a builder. The Casita Way is Design. Bid. Build.: we handle site feasibility, design, and city permits, put the project out to competitive bid among qualified licensed builders, then manage construction on your behalf through final inspection, so you have one point of contact from the first sketch to the keys. We are based in San Diego and serve every jurisdiction in San Diego County, plus Orange County, Riverside County and the Inland Empire, Los Angeles County, and select markets across California.

Almost certainly yes. California law (Gov. Code § 66314 and related statutes) requires every city to allow at least one ADU and one JADU on any residential lot with an existing or proposed single-family home, and cities cannot impose minimum lot sizes for ADUs. What varies by property is how big it can be, where it can sit, and whether utilities and access make it practical — which is exactly what a free Casita site walk answers.

No. Since January 1, 2025, California permanently prohibits cities from requiring owner-occupancy for ADUs (AB 976), so you can rent out both your home and the ADU. The one exception is a Junior ADU (JADU): the owner must live in either the main house or the JADU.

Yes — ADUs can be rented as long-term housing anywhere in California, and rental income is the most common reason San Diego homeowners build one. Short-term rentals under 30 days are regulated city by city (the City of San Diego, for example, requires a short-term residential occupancy license), so check local rules before planning an Airbnb.