How much does an ADU cost in California?
Most detached ADUs in California cost $220K–$400K to build. Garage conversions typically run $60K–$150K. Actual numbers depend on your city, finish level, and site work — here's the breakdown.
California ADU cost by type.
| Scenario | Cost range | Monthly rent | Net payback |
|---|---|---|---|
| Detached · 800 sq ft · mid | $254K–$338K | $1,800–$2,150 | 12.3–21.2 yrs |
| Garage conversion · 450 sq ft · mid | $94K–$125K | $1,000–$1,200 | 8.2–14.2 yrs |
| Attached · 700 sq ft · mid | $202K–$269K | $1,550–$1,850 | 11.4–19.7 yrs |
| JADU · 450 sq ft · mid | $109K–$146K | $1,000–$1,200 | 9.5–16.6 yrs |
MID-RANGE FINISH · YOUR MARKET MAY SHIFT THESE ±5–35%
California ADU cost by region.
Compare the four California ADU types.
New standalone unit in your backyard. Most privacy, highest rent, highest cost.
Convert an existing garage. Fastest and cheapest path to permit for most homeowners.
Added to your primary home. Shares a wall — lower site work cost than detached.
Up to 500 sq ft carved from your primary home. Owner-occupancy required, permit-light.
See your California ADU numbers.
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Where is your property?
California ADU costs and rents vary a lot by market. Use your city or a ZIP.
California ADU cost FAQs.
A typical 800 sq ft detached ADU in California runs $220K–$360K before site-specific work. Garage conversions run $60K–$150K. Bay Area markets average ~25% higher than Sacramento or the Central Valley.
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