Build an ADU in Madison.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Madison — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
4 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Madison zoning ordinance · source · 2026-07-07
- Front
- 75 ft
- Side
- 25 ft
- Rear
- 25 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
Front 75 ft FROM ROAD CENTER LINE. Cul-de-sac 50 ft from ROW. Waterfront 75 ft from MHW.
- Front
- 75 ft
- Side
- 25 ft
- Rear
- 25 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
Grouped with RR. 75 ft centerline.
- Front
- 100 ft
- Side
- 50 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
100 ft from centerline, 50 ft other boundaries.
- Front
- 65 ft
- Side
- 25 ft
- Rear
- 40 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
65 ft centerline / 25 side / 40 rear. Many pre-existing sub-2-ac lots-of-record.
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Madison 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 Madison (Carroll County). A detached ADU can be up to 950 sf.
In Madison's RR zone, ADUs follow the single-family setbacks: 75 ft front, 25 ft side, and 25 ft rear. Madison has 4 zoning districts in total — see the full table below. Confirm your exact zone with the town.