Build an ADU in Windsor.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Windsor — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
- Front setback
- 35 ft
- Side setback
- 25 ft
- Rear setback
- 25 ft
- Max lot coverage
- Varies
- Min lot size
- 217,800 sf (~5.00 ac)
- Max detached ADU
- 950 sf
Figures reflect Windsor's RR 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 Windsor zoning ordinance · source · 2026-07-07
Windsor 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 Windsor (Hillsborough County). A detached ADU can be up to 950 sf.
In Windsor's RR zone, ADUs follow the single-family setbacks: 35 ft front, 25 ft side, and 25 ft rear. Confirm your exact zone with the town.