Build an ADU in Somersworth.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Somersworth — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
15 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Somersworth zoning ordinance · source · 2026-07-04
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Tiered: w/water&sewer 15,000/25/10/30; no service (recorded) 43,560/35/20/50.
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Min lot depth 175 ft.
- Front
- 15 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 10,000 sf (~0.23 ac)
Single non-tiered row.
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Tiered; most conservative recorded.
- Front
- 15 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 10,000 sf (~0.23 ac)
10,000 sf one-unit; two-unit 12,000 sf.
- Front
- 30 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- —
- Min lot
- 26,250 sf (~0.60 ac)
Only w/water&sewer tier defined.
- Front
- 35 ft
- Side
- 20 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
MH Park tier 10,000/25/10/30.
- Front
- 30 ft
- Side
- 20 ft
- Rear
- 30 ft
- Max coverage
- 75% impervious
- Min lot
- 40,000 sf (~0.92 ac)
Commercial tier; 75% max impervious.
- Front
- 70 ft
- Side
- 25 ft
- Rear
- 25 ft
- Max coverage
- 40% building
- Min lot
- —
Front 70 for lots fronting major City road. Coverage 40% building.
- Front
- 10 ft
- Side
- 10 ft
- Rear
- 15 ft
- Max coverage
- 40% building
- Min lot
- 10,000 sf (~0.23 ac)
Commercial 10,000 sf.
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 40% building
- Min lot
- 40,000 sf (~0.92 ac)
Commercial tier.
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 40% building
- Min lot
- 40,000 sf (~0.92 ac)
Commercial tier most conservative.
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 40% building
- Min lot
- 40,000 sf (~0.92 ac)
Commercial tier.
- Front
- 10 ft
- Side
- 10 ft
- Rear
- 10 ft
- Max coverage
- 30% building
- Min lot
- —
Coverage 30% building.
- Front
- 15 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 7,000 sf (~0.16 ac)
3,500 sf per unit.
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Somersworth 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 Somersworth (Strafford County). A detached ADU can be up to 950 sf.
In Somersworth's R-1 zone, ADUs follow the single-family setbacks: 35 ft front, 20 ft side, and 50 ft rear. Somersworth has 15 zoning districts in total — see the full table below. Confirm your exact zone with the town.