Compare ADU zoning rules across 3 Massachusetts cities. Average ADU score: 6.3/10.
| City | Max Size | Setbacks | Permit Fees | Build Cost | 1BR Rent | Score |
|---|---|---|---|---|---|---|
| Boston | Not as-of-right — ZBA variance required (by-right only in Mattapan) | 20 feet (applies to variance/Mattapan detached units) | $4,500-$7,500 | $200,000-$400,000 | $1,800-$2,400/mo | 5/10 |
| Cambridge | 900 sq ft or 50% of primary dwelling, whichever is less (MA state by-right cap) | 5 ft base (ADU setbacks may not be stricter than principal/accessory standards under 760 CMR 71.03) | $3,500-$5,500 | $210,000-$420,000 | $1,900-$2,500/mo | 8/10 |
| Worcester | 900 sq ft by-right (larger is possible via Planning Board special permit) | 5 ft via the accessory-structure standard (R districts) | $2,800-$4,500 | $140,000-$280,000 | $1,250-$1,650/mo | 6/10 |
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