Build an ADU in Harrisville.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Harrisville — 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 Harrisville zoning ordinance · source · 2026-07-07
- Front
- 50 ft
- Side
- 40 ft
- Rear
- 40 ft
- Max coverage
- 30% impervious
- Min lot
- 87,120 sf (~2.00 ac)
Primary district; a district of farms or residences (sec 6.1.1). Min land area 2 acres (87,120 sf) with 250 ft frontage (sec 6.1.2). Front setback is 50 ft measured to the nearest boundary of any public right-of-way (ROW), not centerline; side and rear are 40 ft to lot…
- Front
- 35 ft
- Side
- 35 ft
- Rear
- 35 ft
- Max coverage
- 30% impervious
- Min lot
- 35,000 sf (~0.80 ac)
District of single-family, ADU, duplex and multiple-family residences plus business/for-profit uses (sec 7.1.1). Min frontage 200 ft, min land area 35,000 sf (sec 7.1.3). No building, structure or storage within 35 ft of the nearest edge of any right-of-way or property line…
- Front
- 35 ft
- Side
- 35 ft
- Rear
- 35 ft
- Max coverage
- 30% impervious
- Min lot
- 40,000 sf (~0.92 ac)
District of duplex/multiple-family residences and non-obnoxious manufacturing/business uses (sec 8.1.1). No building or storage within 35 ft of the nearest edge of any right-of-way or property line (sec 8.1.3) - one 35-ft standard for front (from ROW), side and rear.
- Front
- 15 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- 30% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Amended March 2014. Min road frontage 200 ft (200 ft waterline frontage for waterfront lots); min lot 43,560 sf / 1 acre (secs. No structure closer than 15 ft to any right-of-way edge or to side/rear boundaries (sec 9.1.6).
- Front
- 25 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- 30% impervious
- Min lot
- 35,000 sf (~0.80 ac)
District of single-family, duplex and multiple-family residences; ADUs permitted only by special exception from the ZBA (sec 10.1.1). Min frontage 150 ft, min land area 35,000 sf (sec 10.1.2). Front setback 25 ft from the nearest boundary of any public right-of-way; side and…
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Harrisville 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 Harrisville (Cheshire County). A detached ADU can be up to 950 sf.
In Harrisville's RA zone, ADUs follow the single-family setbacks: 50 ft front, 40 ft side, and 40 ft rear. Harrisville has 5 zoning districts in total — see the full table below. Confirm your exact zone with the town.