Build an ADU in Londonderry.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Londonderry — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
11 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Londonderry zoning ordinance · source · 2026-07-04
- Front
- 40 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Min lot 43,560 not on municipal wastewater; may increase by soil.
- Front
- 40 ft
- Side
- 35 ft
- Rear
- 30 ft
- Max coverage
- 55% building
- Min lot
- —
Dev-lot perimeter setbacks. Max footprint 55%.
- Front
- 60 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 25% building
- Min lot
- 43,560 sf (~1.00 ac)
Coverage 25% building. Min lot 1 acre.
- Front
- 60 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 25% building
- Min lot
- 43,560 sf (~1.00 ac)
Same as C-I.
- Front
- 60 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 25% building
- Min lot
- 43,560 sf (~1.00 ac)
Same as C-I.
- Front
- 60 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 25% building
- Min lot
- 43,560 sf (~1.00 ac)
Footprint ≤3,500 sf, height ≤30 ft.
- Front
- 90 ft
- Side
- 45 ft
- Rear
- 30 ft
- Max coverage
- 25% building
- Min lot
- 43,560 sf (~1.00 ac)
Front tiered by footprint (60/90, conservative 90). Side ½ front min 30. Rear ⅓ front min 30.
- Front
- 30 ft
- Side
- 20 ft
- Rear
- 20 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
25% green space (not coverage cap). Min lot 1 acre.
- Front
- 30 ft
- Side
- 20 ft
- Rear
- 20 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Min lot 1 acre.
- Front
- 30 ft
- Side
- 20 ft
- Rear
- 20 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Shares industrial standards.
- Front
- 30 ft
- Side
- 0 ft
- Rear
- 0 ft
- Max coverage
- —
- Min lot
- —
Front 0 (30 if abuts public street, recorded). No min lot.
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Londonderry 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 Londonderry (Rockingham County). A detached ADU can be up to 950 sf.
In Londonderry's AR-I zone, ADUs follow the single-family setbacks: 40 ft front, 15 ft side, and 15 ft rear. Londonderry has 11 zoning districts in total — see the full table below. Confirm your exact zone with the town.