Build an ADU in Plymouth.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Plymouth — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
7 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Plymouth zoning ordinance · source · 2026-07-07
- Front
- 15 ft
- Side
- 10 ft
- Rear
- 10 ft
- Max coverage
- 75% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Town's principal single-family residential district (single-family detached dwelling is a permitted 'P' use, Sec 304). Setbacks measured from the lot line / street right-of-way edge (Sec 303); EXCEPTION: on streets with rights-of-way under 50 ft, the front yard is measured…
- Front
- 15 ft
- Side
- 10 ft
- Rear
- 10 ft
- Max coverage
- 75% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Front yard '15 ft, OR the average front setback of all residential lots within 300 [ft], whichever is less, but no less than 10 feet' (note the MFR floor is 10 ft, vs 5 ft in SFR) - 15 ft recorded as the cap.
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- 75% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Rural/agricultural district; single-family detached dwellings are a permitted 'P' use (Sec 304). Front 30 / side 15 / rear 15 ft Min lot 43,560 sf is the conservative on-site-septic + private-water tier; the utility tiers also show 40,000 sf (a floor stated for both the…
- Front
- 30 ft
- Side
- 10 ft
- Rear
- 10 ft
- Max coverage
- 75% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Civic/institutional district (single-family detached is 'P'). Front 30 / side 10 / rear 10 ft Min lot 43,560 sf conservative on-site-septic + private-water tier; tiers to 20,000 sf where sewer OR public water and where sewer AND public water are present.
- Front
- 0 ft
- Side
- 0 ft
- Rear
- 10 ft
- Max coverage
- 100% impervious
- Min lot
- —
Downtown/village commercial district. Front yard 0 ft with a MAXIMUM front setback of 10 ft (build-to line, 'Maximum yards' row shows 10 ft for VC only). No minimum lot area (table shows '-' / '0' in the VC column across all utility tiers).
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- 75% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Highway commercial corridor (single-family detached allowed only by special exception, Sec 304). Front 30 / side 15 / rear 15 ft Min lot 43,560 sf conservative on-site-septic + private-water tier; tiers to 20,000 sf with sewer OR public water and with sewer AND public water.
- Front
- 30 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- 75% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Industrial and commercial development district (single-family detached allowed only by special exception). Front 30 / side 15 / rear 15 ft Min lot 43,560 sf conservative on-site-septic + private-water tier; tiers to 20,000 sf with sewer OR public water and with sewer 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.
Plymouth 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 Plymouth (Grafton County). A detached ADU can be up to 950 sf.
In Plymouth's SFR zone, ADUs follow the single-family setbacks: 15 ft front, 10 ft side, and 10 ft rear. Plymouth has 7 zoning districts in total — see the full table below. Confirm your exact zone with the town.