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ADU (Accessory Dwelling Unit) Project Costs in Massachusetts

What Massachusetts owners actually declared on 46 recent ADU building permits in our dataset — public-record values, not quotes.

$160,000
Median project value
$15,000–$330,000
Typical range
46
Permits analyzed

Owner-declared values from public building-permit records, residential-scale projects only (commercial and out-of-scale outliers excluded) — a benchmark, not a substitute for a contractor quote.

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FAQ

How much does a ADU project cost in Massachusetts?

Across 46 recent Massachusetts building permits that declared a value, the median ADU project value is $160,000, with a typical range of $15,000 to $330,000. These are owner-declared values from public permit records, not quotes.

Where does this cost data come from?

Every figure is the declared project value on a real building permit filed with a Massachusetts building department — public records MassPermits aggregates, not estimates.