Build an ADU in Plainfield.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Plainfield — 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 Plainfield zoning ordinance · source · 2026-07-07
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- 40% impervious
- Min lot
- 40,000 sf (~0.92 ac)
Principal (densest) residential district: permits single-family dwellings, multi-family (special exception), and both attached and detached ADUs. Minimum lot size is utility-tiered: 20,000 sf with public water AND sewer, 30,000 sf with public water OR sewer, 40,000 sf with NO…
- Front
- 30 ft
- Side
- 20 ft
- Rear
- 30 ft
- Max coverage
- 20% impervious
- Min lot
- 152,460 sf (~3.50 ac)
Minimum lot size 3.5 acres (152,460 sf) - flat, not utility-tiered. Minimum road frontage 200 ft/lot. Setbacks Front 30', Side 20', Rear 30' (linear); front measured from ROW line or from a line 25 ft off the road centerline (Definitions).
- Front
- 30 ft
- Side
- 20 ft
- Rear
- 30 ft
- Max coverage
- —
- Min lot
- 304,920 sf (~7.00 ac)
Minimum lot size 7 acres (304,920 sf). Minimum road frontage 300 ft/lot. Setbacks Front 30', Side 20', Rear 30' (linear); front measured from ROW line or from a line 25 ft off the road centerline (Definitions).
- Front
- 30 ft
- Side
- 20 ft
- Rear
- 30 ft
- Max coverage
- —
- Min lot
- 653,400 sf (~15.00 ac)
Minimum lot size 15 acres (653,400 sf). Minimum road frontage 400 ft/lot. Setbacks Front 30', Side 20', Rear 30' (linear); front measured from ROW line or from a line 25 ft off the road centerline (Definitions).
- Front
- —
- Side
- —
- Rear
- —
- Max coverage
- —
- Min lot
- 1,089,000 sf (~25.00 ac)
Open-space / conservation district. Minimum lot size 25 acres (1,089,000 sf). The ordinance lists NO setbacks, lot coverage, road frontage or building height for CON because permanent residential structures are not a base use.
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Plainfield 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 Plainfield (Sullivan County). A detached ADU can be up to 950 sf.
In Plainfield's VR zone, ADUs follow the single-family setbacks: 30 ft front, 15 ft side, and 15 ft rear. Plainfield has 5 zoning districts in total — see the full table below. Confirm your exact zone with the town.