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Bay Area ADU Builders
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Can you build an ADU, and what will it cost?

Pick your city. You'll see what it allows, what it charges, and which licensed builders work there, all from the city's own pages and the state license board.

A detached ADU of 750 sq ft runs $350k to $465k to build by our estimate, plus city fees of $2,832 to $13,092 where cities publish a total.

Cities
18 cities checked
Builders
24 licensed builders ranked
Checked
Data checked Oct 18, 2026

Example: what San Jose allows on a typical lot

ADU rules in San Jose drawn on a typical lot Detached ADU, City standards: up to 1,200 square feet, 4 feet from side and rear lot lines, 18 feet tall. Parking: None required. Rear lot line Street Main house ADU up to 1,200 sq ft 18 ft tall 0–4 ft 0–4 ft 6 ft apart Parking: none required
Detached ADU, City standards. Not to scale.

From the city's own ADU checklist, read Oct 18, 2026. All San Jose rules and sources

ADU rules by city

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Building in Cupertino? Compare ADU builders in Cupertino by project type, then use the local permit and quote checklist before you hire.

South Bay

Peninsula

San Francisco

East Bay

What it costs

City fees and the build price are different numbers, so we keep them apart. The city fees are the city's own averages. The build price is our estimate for a 750 sq ft detached ADU. How we estimate it

$350k–465k

to build 750 sq ft detached, our estimate

Estimate your ADU in San Jose

City fees for a detached ADU, where the city publishes a total

From each city's own fee estimator; sources on each city's cost page. Only cities that publish a total are shown. School and utility fees are extra everywhere.

Top-scoring licensed builders

All 24