Build an ADU in Dunbarton.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Dunbarton — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
5 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Dunbarton zoning ordinance · source · 2026-07-07
- Front
- 50 ft
- Side
- 50 ft
- Rear
- 50 ft
- Max coverage
- 15% impervious
- Min lot
- 217,800 sf (~5.00 ac)
Default/principal district: LDR is all land in town not in the Village or Medium-Density districts (Art III.B.1.b); single-family dwellings permitted by right (Art IV Table of Uses). Min lot 5 acres (217,800 sf), frontage 300 ft, setbacks 50/50/50, septic-system setback 50…
- Front
- 40 ft
- Side
- 40 ft
- Rear
- 40 ft
- Max coverage
- 15% impervious
- Min lot
- 130,680 sf (~3.00 ac)
Corridor district around Route 13/Tenney Hill area (metes-and-bounds in Art III.B.1.c). Min lot 3 acres (130,680 sf) per dwelling unit, frontage 250 ft, setbacks 40/40/40, septic setback 50 ft, well setback 75 ft, max height 35 ft, 15% lot coverage (buildings + impervious…
- Front
- 40 ft
- Side
- 40 ft
- Rear
- 40 ft
- Max coverage
- 15% impervious
- Min lot
- 87,120 sf (~2.00 ac)
Small district along Route 13 at the town center (300-ft-deep band, Art III.B.1.a). Min lot 2 acres (87,120 sf) per dwelling unit, frontage 200 ft, setbacks 40/40/40, septic setback 50 ft, well setback 75 ft, max height 35 ft, 15% lot coverage (buildings + impervious surfaces).
- Front
- 150 ft
- Side
- 100 ft
- Rear
- 100 ft
- Max coverage
- 15% impervious
- Min lot
- —
Overlay zone along both sides of NH Routes 13 and 77 for lots fronting on (or with direct access easements to) those highways (Art III.B.1.d); governs multi-family projects (Art 9). Min lot size and frontage are 'per underlying district'; the table then imposes larger…
- Front
- —
- Side
- —
- Rear
- —
- Max coverage
- —
- Min lot
- —
Overlay superimposed on all districts, mapped from the National Wetlands Inventory with field delineation by a Certified Wetland Scientist controlling (Art V.B, F).
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Dunbarton 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 Dunbarton (Merrimack County). A detached ADU can be up to 950 sf.
In Dunbarton's LDR zone, ADUs follow the single-family setbacks: 50 ft front, 50 ft side, and 50 ft rear. Dunbarton has 5 zoning districts in total — see the full table below. Confirm your exact zone with the town.