Build an ADU in Henniker.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Henniker — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
9 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Henniker zoning ordinance · source · 2026-07-07
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 217,800 sf (~5.00 ac)
The town's principal low-density single-family district covering most land outside the village ('agriculture and low-density rural living outside of the built-up districts... where public water and sewer services are not generally available', 133-25).
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
Mixture of single- and two-family homes in neighborhoods removed from the center village (133-23). FRONT 30 ft from the public RIGHT-OF-WAY, except a building may be built in line with existing adjacent buildings on the same lot (133-24.E).
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Residential area in the built-up town center (133-21). FRONT 30 ft from the public RIGHT-OF-WAY, except a building may be built in line with existing adjacent buildings on the same lot (133-22.D). Min lot TIERED BY UTILITIES: 10,000 sf with town water AND sewer; 1 acre…
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Village-center business district; single-family, two-family and multi-unit dwellings and cottage court housing also permitted by right (133-32). Setbacks per the all-commercial-districts rule: FRONT 30 ft from the public RIGHT-OF-WAY (may build in line with existing adjacent…
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
Business area outside the village for light-manufacturing commerce; single-family and two-family dwellings and manufactured housing also permitted by right (133-30). FRONT 30 ft from the public RIGHT-OF-WAY (may build in line with existing adjacent buildings on the same lot);…
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 65,340 sf (~1.50 ac)
Commercial sales/services complementing the recreational area (Pats Peak vicinity); single-family and two-family dwellings, multi-unit dwellings and manufactured housing also permitted by right (133-31).
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
Business/manufacturing area outside the village with highway access (133-29). FRONT 30 ft from the public RIGHT-OF-WAY (may build in line with existing adjacent buildings on the same lot); side/rear 15 ft (133-28.B-C).
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 217,800 sf (~5.00 ac)
US Army Corps of Engineers flood-storage land for the Hopkinton flood control dam (eastern/southeastern lowlands, 133-34/133-35). Not developable in practice: all uses and structures must be specifically authorized by the USACE, and must additionally conform to ALL…
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- —
OVERLAY district (New England College area) superimposed on base districts; it adds educational uses (classrooms, dorms by special exception, etc.) on top of everything the underlying district allows (133-33.A).
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Henniker 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 Henniker (Merrimack County). A detached ADU can be up to 950 sf.
In Henniker's RR zone, ADUs follow the single-family setbacks: 30 ft front, 15 ft side, and 15 ft rear. Henniker has 9 zoning districts in total — see the full table below. Confirm your exact zone with the town.