Build an ADU in Farmington.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Farmington — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
8 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Farmington zoning ordinance · source · 2026-07-06
- Front
- 25 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Primary single-family residential district (Sec 2.02, purpose = medium-density residential development). Min lot 1 acre (43,560 SF). Single-family density 1 unit/acre; duplex 1 unit/21,782 SF; multi-family 1 unit/14,520 SF.
- Front
- 50 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 130,680 sf (~3.00 ac)
Rural/agricultural base district (Sec 2.01). Min lot 3 acres (130,680 SF); density 1 dwelling unit per 3 acres plus 1 ADU. Front setback 50 ft; side and rear 15 ft for principal residential and accessory buildings; non-residential/agricultural buildings 1 ft per ft of height,…
- Front
- 25 ft
- Side
- 15 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 43,560 sf (~1.00 ac)
Low-to-medium density open-space residential district (Sec 2.03). Min lot 1 acre (43,560 SF); max new residential density 1 dwelling unit per acre plus 1 ADU. Min street frontage 150 ft Max height 35 ft residential / 55 ft non-residential.
- Front
- 25 ft
- Side
- 15 ft
- Rear
- 25 ft
- Max coverage
- —
- Min lot
- 30,000 sf (~0.69 ac)
Higher-density district around downtown (Sec 2.04). Min street frontage 75 ft Max height 55 ft No lot-coverage % in table. Front setback also subject to a uniform-streetwall rule (footnote 6): must match existing uniform setback where one exists, else 25 ft Lots must meet NH…
- Front
- —
- Side
- —
- Rear
- —
- Max coverage
- —
- Min lot
- 8,000 sf (~0.18 ac)
Compact mixed-use town center (Sec 2.05). Min lot 0.20 acre (8,000 SF). Single-family detached permitted by right, but lots relying on Main/Central/Spring Street for frontage prohibit ground-floor residential (must be mixed-use above commercial).
- Front
- 50 ft
- Side
- 30 ft
- Rear
- 30 ft
- Max coverage
- —
- Min lot
- 87,120 sf (~2.00 ac)
Commercial/office district (Sec 2.06); single-family detached NOT permitted (Table 2.00(C)) — residential only as mixed-use, 1 unit per 1,000 SF gross commercial floor area on 2nd floor or above. Min lot 2 acres (87,120 SF).
- Front
- 20 ft
- Side
- 10 ft
- Rear
- 10 ft
- Max coverage
- 80% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Mixed-use gateway district on NH Routes 11/153 (Sec 2.07); single-family detached NOT permitted (Table 2.00(C)); duplex/multi-family are conditional-use permits (CUP); mixed-use by right. Setbacks and lot size tier by frontage: lots abutting Route 11 or 153 = 2-acre min lot,…
- Front
- 20 ft
- Side
- 10 ft
- Rear
- 10 ft
- Max coverage
- 80% impervious
- Min lot
- 43,560 sf (~1.00 ac)
Smaller mixed-use gateway district on Route 11, on municipal water and sewer (Sec 2.08); single-family detached NOT permitted (Table 2.00(C)); duplex/multi-family are CUP; mixed-use by right. Setbacks and lot size tier by frontage: lots abutting Route 11 = 1.5-acre min lot,…
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Farmington 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 Farmington (Strafford County). A detached ADU can be up to 950 sf.
In Farmington's SR zone, ADUs follow the single-family setbacks: 25 ft front, 15 ft side, and 15 ft rear. Farmington has 8 zoning districts in total — see the full table below. Confirm your exact zone with the town.