Build an ADU in Northfield.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Northfield — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
6 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Northfield zoning ordinance · source · 2026-07-07
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 20 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
Principal single-family district ('all other areas of Town' plus 500-ft extensions along Class V+ roads into the Conservation zone). FRONT SETBACK IS MEASURED FROM THE NEAREST RIGHT-OF-WAY of an abutting road (Table 2 row label), not the centerline.
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 20 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Higher-density mixed residential zone near town services (west of I-93/railroad areas). Min lot for a single-family residence is UTILITY-TIERED: 1.00 acre (43,560 sf) WITHOUT public sewer (conservative tier recorded) / 0.50 acre with public sewer.
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 20 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Commercial/industrial corridor near I-93 with municipal sewer and water. Min lot recorded is the NON-RESIDENTIAL tier: 1.00 acre (43,560 sf) without public sewer (conservative) / 0.50 acre with public sewer.
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 20 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Commercial/industrial zone along Rt. 140 to the town line (no municipal sewer/water presumption). Min lot recorded is the NON-RESIDENTIAL tier: 1.00 acre (43,560 sf) without public sewer (conservative) / 0.50 acre with public sewer.
- Front
- 100 ft
- Side
- 50 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- 217,800 sf (~5.00 ac)
Large rural/watershed-protection zone discouraging scattered growth. Single-family AND two-family residences ARE permitted (Table 1 'P') at 5.00 acres (217,800 sf) min lot, with or without public sewer — no utility tiering.
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 20 ft
- Max coverage
- —
- Min lot
- 217,800 sf (~5.00 ac)
Recreation/leisure/agricultural zone along the Winnipesaukee River between Rt. Single-family residence permitted at 5.00 acres (217,800 sf), with or without public sewer — no utility tiering. Front setback 35 ft from nearest right-of-way; side/rear 20 ft each.
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Northfield 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 Northfield (Merrimack County). A detached ADU can be up to 950 sf.
In Northfield's R-1 zone, ADUs follow the single-family setbacks: 35 ft front, 20 ft side, and 20 ft rear. Northfield has 6 zoning districts in total — see the full table below. Confirm your exact zone with the town.