Boston adu construction pricing per square foot
ADU Construction cost per square foot in Boston, Massachusetts in 2026.
Low
$204,000
Average
$306,000
High
$408,000
Boston crews quote about $340 – $680 per square foot.
Multiply local unit rates by your real measurements.
What drives adu construction prices in Boston
Local labor, permitting and climate move Boston prices away from the national average.
Labor market
Boston labor is scarce and expensive, with a short outdoor construction season.
Permits
City permits, licensed-contractor rules and historic review are common.
Climate
Nor easters, ice dams and freeze-thaw drive roofing and insulation costs.
Boston unit pricing by material
Ways to lower your Boston 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.
Boston questions
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