Build an ADU in Mont Vernon.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Mont Vernon — 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 Mont Vernon zoning ordinance · source · 2026-07-07
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- 217,800 sf (~5.00 ac)
Covers all land not inside the Residential (R) or Limited Commercial (LC) districts (I-203) - the large majority of town. Setbacks are measured 'from property line to building line' (Table I-304.2) and are the same in every buildable soil district: front 50, side 30, rear 50.
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- 217,800 sf (~5.00 ac)
The village district: land and buildings within 500 ft of the centerline of the streets listed in I-202 (Main St, Blood Rd, Harwood Rd, Grand Hill Rd, Boutwell Rd, Smith Rd, Hillcrest Ave, parts of Old Wilton Rd/New Boston Rd).
- Front
- 60 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- 50% building
- Min lot
- 87,120 sf (~2.00 ac)
Small commercial pocket on NH Rt 13 near the Milford line (I-204). Yards per Table I-405.3(a)(iv), measured FROM THE NEAREST EDGE OF THE RIGHT-OF-WAY for road frontages: 60 ft from the Rt 13 ROW (recorded as front); 30 ft from the ROW of any access/frontage road; 100 ft from…
- Front
- —
- Side
- —
- Rear
- —
- Max coverage
- 70% impervious
- Min lot
- —
The Mont Vernon portion of the New Boston Air Station (I-601). There are NO minimum road frontage, setback, or height requirements for structures within the development envelope (I-601.4(a)(vii)), so setbacks are recorded null.
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Mont Vernon 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 Mont Vernon (Hillsborough County). A detached ADU can be up to 950 sf.
In Mont Vernon's RR zone, ADUs follow the single-family setbacks: 50 ft front, 30 ft side, and 50 ft rear. Mont Vernon has 4 zoning districts in total — see the full table below. Confirm your exact zone with the town.