Build an ADU in Dorchester.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Dorchester — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
- Front setback
- 50 ft
- Side setback
- 50 ft
- Rear setback
- 50 ft
- Max lot coverage
- 20%
- Min lot size
- 87,120 sf (~2.00 ac)
- Max detached ADU
- 950 sf
Figures reflect Dorchester's RURAL residential zone and are a planning aid — your parcel's exact zone and overlays (wetland, shoreland) are verified before we lock your price.
Verified against the official Dorchester zoning ordinance · source · 2026-07-07
Dorchester ADU FAQ
Yes. Under NH RSA 674:71-73 (HB 577), one accessory dwelling unit is allowed by-right on single-family lots statewide, including Dorchester (Grafton County). A detached ADU can be up to 950 sf.
In Dorchester's RURAL zone, ADUs follow the single-family setbacks: 50 ft front, 50 ft side, and 50 ft rear. Confirm your exact zone with the town.