How much does adu construction cost in Brentwood?

Most Brentwood projects land between $174,000 – $348,000, with an average near $261,000. Local crews quote roughly $290 – $580 per square foot.

What is included in the Brentwood price per square foot?

Typically materials, labor and cleanup. Permits, disposal and access challenges are usually quoted separately.

Unit pricing

ADU Construction cost per square foot in Brentwood

ADU Construction cost per square foot in Brentwood, California in 2026.

Low

$174,000

Average

$261,000

High

$348,000

Brentwood crews quote about $290 – $580 per square foot.

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Multiply local unit rates by your real measurements.

What drives adu construction prices in Brentwood

Local labor, permitting and climate move Brentwood prices away from the national average.

Labor market

Licensed Brentwood contractors carry California workers' comp and prevailing wage pressure, and crews here quote roughly 16% above the national labor average. Demand in the Bay Area market peaks in spring, so booking early usually beats a rush premium.

Permits

Brentwood follows the California Building Standards Code, so most structural, electrical, plumbing and re-roof work needs a permit from the Brentwood building department plus Title 24 energy compliance. Bay Area seismic retrofit standards and strict energy upgrades are common conditions of approval.

Climate

Brentwood sits in a mild marine climate with heavy winter rain, so expect proper drainage, moisture detailing and a dry-season schedule for exterior work.

Brentwood unit pricing by material

Prefab studio ADU$270 – $370

Site-built 1-bedroom$370 – $485

Site-built 2-bedroom$485 – $630

Custom high-end ADU$630 – $870

Ways to lower your Brentwood price

Use pre-approved ADU plans where your city offers them — saves months and design fees.
Detach only if required; attached and conversion ADUs cost far less.
Collect three written bids on an identical scope — spreads of 20–40% are normal.
Book in the off-season and stay flexible on the start date to save 5–15%.
Bundle nearby work into one mobilization so you only pay setup and travel once.
Ask what the contractor would change to cut 10% without hurting durability.

Brentwood questions

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