Build an ADU in Windham.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Windham — 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 Windham zoning ordinance · source · 2026-07-06
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 20% building
- Min lot
- 50,000 sf (~1.15 ac)
PRIMARY single-family residential district and Windham's predominant residential zone (Section 602; Table of Requirements p.149). Min lot FRONTAGE 175 ft, measured 50 ft back from the front lot line (Note #2).
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 20% building
- Min lot
- 50,000 sf (~1.15 ac)
Section 603. Table of Requirements: min frontage 175 ft; front yard 50 ft; side 30 ft; rear 30 ft; max building coverage 20% of lot; min floor area 1,000 sf per dwelling. minLotSqft is the 50,000 sf ordinance floor (30,000 sf contiguous); actual minimum is soil-type-driven…
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 20% building
- Min lot
- 50,000 sf (~1.15 ac)
Section 603. Table of Requirements base row for single-family: min frontage 175 ft, front 50 ft, side 30 ft, rear 30 ft, max building coverage 20%, min floor area 750 sf per dwelling. Dimensional requirements SCALE UP with unit count: frontage is 175 ft plus 30 ft per…
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 20% building
- Min lot
- 50,000 sf (~1.15 ac)
Section 603. Table of Requirements: min frontage 175 ft plus 30 ft per additional dwelling unit; front 50 ft; side 30 ft plus 10 ft per additional dwelling unit (footnote 7); rear 30 ft plus 10 ft per additional dwelling unit (footnote 8); max building coverage 20%; min floor…
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- 30% building
- Min lot
- 50,000 sf (~1.15 ac)
Section 604. Table of Requirements: min frontage 175 ft; front yard 50 ft; side yard 30 ft; rear yard 30 ft; max building coverage 30% of lot; min floor area per dwelling 0 (no residential floor-area minimum — a single dwelling unit is allowed only as an accessory use…
- Front
- 75 ft
- Side
- 20 ft
- Rear
- 30 ft
- Max coverage
- 30% building
- Min lot
- 50,000 sf (~1.15 ac)
Section 605. Business Commercial A and B share ONE Table of Requirements row. Min frontage 175 ft; FRONT yard 75 ft; side yard 20 ft (footnote 6: 50 ft where it abuts a Residential District); rear yard 30 ft (footnote 6: 50 ft where it abuts a Residential District); max…
- Front
- 75 ft
- Side
- 20 ft
- Rear
- 30 ft
- Max coverage
- 30% building
- Min lot
- 50,000 sf (~1.15 ac)
Section 617. Shares the same Table of Requirements row as Business Commercial A: min frontage 175 ft; front yard 75 ft; side yard 20 ft (50 ft where abutting a Residential District, footnote 6); rear yard 30 ft (50 ft where abutting a Residential District, footnote 6); max…
- Front
- 0 ft
- Side
- 0 ft
- Rear
- 0 ft
- Max coverage
- 70% building
- Min lot
- —
Section 618. Table of Requirements: min lot FRONTAGE 50 ft (on a Class V-or-better road; frontage along I-93 not counted, 618). Front/side/rear yard setbacks are 0 (footnotes 13, 14, and 618 text: 'no front, side or rear lot line setback requirements') EXCEPT a 50 ft minimum…
- Front
- 50 ft
- Side
- 20 ft
- Rear
- 30 ft
- Max coverage
- 30% building
- Min lot
- 50,000 sf (~1.15 ac)
Section 606. Table of Requirements: min frontage 175 ft; front yard 50 ft; side yard 20 ft (footnote 6: 50 ft where it abuts a Residential District); rear yard 30 ft (footnote 6: 50 ft where it abuts a Residential District); max building coverage 30% of lot; min floor area…
- Front
- 30 ft
- Side
- 20 ft
- Rear
- 0 ft
- Max coverage
- 100% building
- Min lot
- —
Section 612. Table of Requirements: min lot FRONTAGE 50 ft; front yard 30 ft; side yard 20 ft; rear yard 0 ft; max building coverage 100% of lot; min floor area per dwelling 0. 'There shall be NO minimum lot size' (612), so minLotSqft is null (VCD is expressly exempted from…
- Front
- 50 ft
- Side
- 20 ft
- Rear
- 30 ft
- Max coverage
- 30% building
- Min lot
- 50,000 sf (~1.15 ac)
Section 614. Table of Requirements: min frontage 175 ft; front yard 50 ft; side yard 20 ft (footnote 6: 50 ft where it abuts a Residential District); rear yard 30 ft (footnote 6: 50 ft where it abuts a Residential District); max building coverage 30% of lot; min floor area…
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Windham 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 Windham (Rockingham County). A detached ADU can be up to 950 sf.
In Windham's RURAL zone, ADUs follow the single-family setbacks: 50 ft front, 30 ft side, and 30 ft rear. Windham has 11 zoning districts in total — see the full table below. Confirm your exact zone with the town.