How big can an ADU be in Farmington?

350 to 950 sq ft; max 2 bedrooms, per §6.01(B)(4) as read 2026-11-15.

Does the owner have to live on the lot in Farmington?

Owner must live in the house or the ADU; restrictive covenant recorded (§6.01(B)(2), (C)).

Can an ADU in Farmington be detached?

Attached or detached, one per lot, by right, under §6.01(B)(1).

Strafford County · New Hampshire

ADU rules in Farmington, NH

Farmington is a Strafford County town on the Cocheco River.

Farmington is in our service area. This page covers what the town ordinance says about ADUs.

Call (978) 987-0089

Town ADU rules

What’s allowed on your lot in Farmington.

Farmington allows one ADU of 350 to 950 sq ft by right in every district that allows a single-family home.

Size limit: 350 to 950 sq ft; max 2 bedrooms
Where it can go: Attached or detached, one per lot, by right
Owner on site: Owner must live in the house or the ADU; restrictive covenant recorded
Parking: No ADU parking rule in the zoning ordinance
Approval: By right in every district that allows single-family homes
Water setback: No buildings within 100 ft of water bodies (50 ft in UR) without a Special Use Permit; erosion controls within 250 ft

Allowed

ApprovalAn ADU is permitted by right in every district that allows single-family dwellings.§6.01(B)
Attached or detachedOne ADU, attached or detached, is allowed by right.§6.01(B)(1)
Attached or detachedDefinitions: attached = within or physically connected to the house, or completely inside a preexisting detached structure. Detached = neither of those.§1.14 Definitions
Owner on siteThe owner must live in the ADU or the main house. If the owner moves out, fines under RSA 676:17 until an owner moves back or the ADU is discontinued. Owners away on things like military duty may ask the Selectmen for relief.§6.01(B)(2), (C)
SizeAt least 350 sq ft and no more than 950 sq ft.§6.01(B)(4)
OtherMaximum two bedrooms.§6.01(B)(5)
OtherThe owner must sign a restrictive covenant in favor of the town, covering ownership and condo conversion. It is recorded at the Strafford County Registry of Deeds before the certificate of occupancy.§6.01(D)(1)
OtherHome occupations are allowed in the ADU with the property owner's consent.§6.01(B)(8)
OtherTo discontinue an ADU, the owner notifies the Code Enforcement Officer while it is empty, and the CO is revoked.§6.01(E)(1)
LotAR and RR density tables count one ADU on top of the base density.Table 2.01(B); Table 2.03(B)
ShorelandWaterfront Protection Overlay District. Limited Development Zone: within 100 ft of any water body (50 ft in the Urban Residential District). Only forestry, agriculture, wildlife refuges, parks, trails, open space and wells are permitted there; other uses need a Planning Board Special Use Permit. Controlled Development Zone: within 250 ft of any water body; development needs proper erosion control. Water bodies = over 5 acres, or streams that flow 12 months in the average year. The ordinance does not reference RSA 483-B.§4.03(A)-(B); definition WATER BODIES §1.14

Not allowed

Not allowedNo ADU with attached single-family dwellings such as townhouses.§6.01(B)(6)
Not allowedNo ADU on rented or leased land.§6.01(B)(7)
Not allowedNo separate condominium conveyance of the ADU.§6.01(B)(3)
Not allowedNo more than one ADU; no more than two bedrooms; no ADU over 950 sq ft.§6.01(B)(1), (4), (5)
Not allowedNo single-family homes, so no ADUs, in CB, MU-E or MU-W.Table 2.00(C)

Read 2026-11-15 from Town of Farmington Zoning Ordinance ("Zoning Ordinance - 2026" on the town Zoning Ordinance page) (Header: "As Amended March 19, 2025"; history line lists amendments through "March 19, 2025; and March 11, 2026". The two dates conflict; the 2026 history entry suggests the text includes March 11, 2026 amendments.). Anything not listed here, we check with the Farmington land-use office for your lot.

Setbacks

Front, side and rear in Farmington.

NH RSA 674:71-73 (HB 577) - one attached or detached ADU by right on a single-family lot

Farmington's dimensional table, as printed in the ordinance.

District	Front	Side	Rear	Lot / cover / height
ARprimaryAgricultural ResidentialTable 2.01(B); §2.01(C) requires 40,000 sf contiguous buildable area without town water/sewer. AR frontage 250 feet. AR accessory buildings: Accessory Buildings or Structures 15 feet (side and rear).	50 feet	15 feet	15 feet	3 acres · No coverage limit in table · Height Residential Buildings 35 feet (Non-Residential 55 feet)
SRSuburban Residential DistrictTable 2.02(B); §2.02(D) requires 30,000 sf contiguous buildable area without town water/sewer. SR frontage 150 feet. SR accessory buildings: Accessory Buildings or Structures 15 feet (side and rear).	25 feet	15 feet	15 feet	1 acre (43,560 SF) · No coverage limit in table · Height Residential Buildings 35 feet (Non-Residential 55 feet)
RRRural Residential DistrictTable 2.03(B); §2.03(D) requires 30,000 sf contiguous buildable area without town water/sewer. RR frontage 150 feet. RR accessory buildings: Accessory Buildings or Structures 15 feet (side and rear).	25 feet	15 feet	15 feet	1 acre (43,560 SF) · No coverage limit in table · Height Residential buildings 35 feet (Non-residential 55 feet)
URUrban Residential DistrictTable 2.04(B). UR frontage 75 feet. UR accessory buildings: Accessory Buildings or Structures 15 feet (side and rear).	25 feet (or the existing uniform setback of the street)	15 feet	15 feet	30,000 SF (lots must also meet Env-Wq 1000 soil-based lot size) · No coverage limit in table · Height Residential Buildings 55 feet
VCVillage Center DistrictTable 2.05(B); §2.05(C)(2): on lots using Main, Central or Spring Street frontage, residential is prohibited unless it is mixed use above first-floor commercial. VC frontage 50 feet. VC accessory buildings: Accessory building not closer to the front lot line than the principal building.	Keep the existing uniform setback relationship to the street	None except where residential buffer applies	None except where residential buffer applies	0.20 Acre (8,000 SF) · No coverage limit in table · Height Residential Buildings 55 feet

Verified 2026-11-15 against Town of Farmington Zoning Ordinance ("Zoning Ordinance - 2026" on the town Zoning Ordinance page). Towns amend ordinances, so confirm with the land-use office before you build. Official source

FAQ

ADUs in Farmington.

How big can an ADU be in Farmington?: 350 to 950 sq ft; max 2 bedrooms, per §6.01(B)(4) as read 2026-11-15.
Does the owner have to live on the lot in Farmington?: Owner must live in the house or the ADU; restrictive covenant recorded (§6.01(B)(2), (C)).
Can an ADU in Farmington be detached?: Attached or detached, one per lot, by right, under §6.01(B)(1).

Planning an ADU in Farmington?

Call (978) 987-0089 and we will read the ordinance against your lot. See the ADU models

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