Build an ADU in Loudon.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Loudon — 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 Loudon zoning ordinance · source · 2026-07-06
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 40 ft
- Max coverage
- 20% impervious
- Min lot
- 87,120 sf (~2.00 ac)
PRIMARY single-family residential district (townwide). Min lot area 2 acres (87,120 sf) for single-family; two-family requires 3 acres (130,680 sf). Min frontage 200 ft single-family / 250 ft two-family.
- Front
- 15 ft
- Side
- 15 ft
- Rear
- 25 ft
- Max coverage
- 40% impervious
- Min lot
- 40,000 sf (~0.92 ac)
Compact village district (smallest lots, Loudon Village). Min frontage 125 ft Contiguous buildable area >= 30,000 sf (2022).
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 40 ft
- Max coverage
- —
- Min lot
- 217,800 sf (~5.00 ac)
Most-restrictive rural preservation district. Min lot area 5 acres (217,800 sf). Min frontage 400 ft Contiguous buildable area >= 1.5 acres (65,340 sf) required (2022). COVERAGE: S 205.4 (Area and Frontage Requirements) sets NO coverage percentage for AFP - the ordinance…
- Front
- 60 ft
- Side
- 30 ft
- Rear
- 40 ft
- Max coverage
- 50% impervious
- Min lot
- 87,120 sf (~2.00 ac)
Commercial/Industrial district (no dwellings permitted; commercial and industrial uses only - S 206.2/206.3). Min lot area 2 acres (87,120 sf) commercial / 5 acres (217,800 sf) industrial. Min frontage 200 ft commercial / 300 ft industrial.
- Front
- 60 ft
- Side
- 30 ft
- Rear
- 40 ft
- Max coverage
- 50% impervious
- Min lot
- 87,120 sf (~2.00 ac)
Commercial/Recreational district (regulates land owned/occupied by NHMS motor speedway - S 207.1). Min lot area 2 acres (87,120 sf) commercial / 5 acres (217,800 sf) industrial / 100 acres (4,356,000 sf) sports facilities.
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Loudon 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 Loudon (Merrimack County). A detached ADU can be up to 950 sf.
In Loudon's RR zone, ADUs follow the single-family setbacks: 50 ft front, 30 ft side, and 40 ft rear. Loudon has 5 zoning districts in total — see the full table below. Confirm your exact zone with the town.