Strafford County · New Hampshire
ADU rules in Milton, NH
Milton is a Strafford County town on the Salmon Falls River and the Maine line.
Milton is in our service area. This page covers what the town ordinance says about ADUs.
Town ADU rules
What’s allowed on your lot in Milton.
Milton rewrote parts of its ADU article in March 2026. An ADU can be up to 1,000 sq ft with an ADU building and occupancy permit.
- Size limit
- Max 1,000 sq ft (town may not cap below 750 sq ft); max 2 bedrooms; max 4 occupants
- Where it can go
- One per lot; definitions cover attached and detached units
- Owner on site
- Owner must live in the house or the ADU; only one unit may be rented
- Parking
- One extra off-street space, for a minimum total of three
- Approval
- ADU-specific building permit and occupancy permit
- Water setback
- No primary structure within 50 ft of public waters; Shoreland overlay covers 250 ft, 20% impervious cap
Allowed
- ApprovalEach ADU needs to meet zoning dimensional rules, an ADU-specific building permit and an occupancy permit.Art. XXI.V.A
- How manyOne ADU, only on a legal lot of record with one existing conforming single-family detached house, no other ADU, and not a duplex.Art. XXI.IV.A.1-3
- Attached or detachedThe text defines both attached and detached units. But the ADU definition also says the unit is 'attached to or contained within an existing single-family dwelling'.Art. XXI.III.A-C
- SizeMaximum 1,000 sq ft. The town will not cap an ADU below 750 sq ft.Art. XXI.VI.B.1; III.A
- DesignInterior door required between house and ADU (need not stay unlocked). Architecture must match the house. No exterior stairway to the ADU on the front of the house.Art. XXI.VI.B.3, 4, 6
- DesignAttached ADUs may have their own entrance or use a shared common space; the town will not limit the choice.Art. XXI.VII.A.5
- ParkingOne off-street space on top of those required for the house, for a minimum total of three.Art. XXI.VI.B.5
- HeightNew ADU construction follows single-family standards: setbacks, height limits, and lot coverage (coverage only in the Comprehensive Shoreland Protection Zone).Art. XXI.VI.A
- LotADUs may be converted from existing nonconforming structures, including detached garages, even if they violate current setbacks or coverage.Art. XXI.VI.D
- Owner on siteThe owner of the whole property must live in the ADU or the house. Only one unit may be rented.Art. XXI.VII.A.2
- OtherMaximum two bedrooms; no more than four people living in the ADU.Art. XXI.VI.B.7; VII.A.3
- SepticAdequate water and sewage per RSA 485-A:38; separate connections not required. Septic application required before building; NH DES septic loading must be met.Art. XXI.VI.B.8; VII.A.4
- OtherA separate electrical panel and service are allowed.Art. XXI.VII.A.4 (second item numbered 4)
- OtherA conforming ADU does not count against the lot's density.Art. XXI.VI.C
- ShorelandShoreland Protection Overlay District covers land within 250 ft of the reference line of public waters (named lakes, ponds, rivers and brooks). The protected buffer for first-order streams is 35 ft. No primary structure within 50 ft of the public boundary; sheds and gazebos (not garages) inside 50 ft need a CUP. Natural woodland buffer within 150 ft. Max 2 1/2 stories or 35 ft. Impervious cover max 20 percent. New on-site septic lots need 150 ft of shore frontage. Definitions follow RSA 483-B:4, and the buffer rules cite RSA 483-B:9. Base-table note: septic at least 75 ft from a stream, brook, lake, river or pond outside the overlay.Art. XVII.C-I; Table of Principal Uses note 1
- State lawThe town text still requires an interior door. State law lets the owner choose how an attached ADU is entered.RSA 674:72, III
Not allowed
- Not allowedNo separate sale or condominium conveyance of the ADU.Art. XXI.VII.A.1
- Not allowedNo ADU with multi-family uses or on rented or leased land.Art. XXI.VII.A.3 (second item numbered 3)
- Not allowedNo ADU on a lot that already has an ADU or is a duplex; the house must be an existing conforming single-family detached dwelling.Art. XXI.IV.A
- Not allowedNo exterior stairway to the ADU on the front of the house.Art. XXI.VI.B.6
- Not allowedNo more than two bedrooms or four occupants.Art. XXI.VI.B.7; VII.A.3
- Not allowedNo single-family homes, so no ADUs, in IC.§3.5 Table of Principal Uses
Read 2026-11-15 from Zoning Ordinance, Town of Milton, New Hampshire (Cover: revision list ending "Revised 3/11/2026"; Art. XXI header "(Adopted 3/14/18, Revised 3/11/26)"). Anything not listed here, we check with the Milton land-use office for your lot.
Setbacks
Front, side and rear in Milton.
NH RSA 674:71-73 (HB 577) - one attached or detached ADU by right on a single-family lot
Milton's dimensional table, as printed in the ordinance.
| District | Front | Side | Rear | Lot / cover / height |
|---|---|---|---|---|
| HDRprimaryHigh Density Residential ZoneTable of Dimensional Requirements, Art. III; §3.2.b.1 (HDR benefits require municipal water and sewer). HDR frontage 75 feet. HDR accessory buildings: Not stated separately. | 10 feet | 15 feet | 10 feet | 0.5 acre · No base-district limit; 20% impervious in Shoreland Protection Overlay (Art. XVII.H.7) · Height 35 feet (excludes silos, steeples and similar structures) |
| CRCommercial Residential ZoneTable of Dimensional Requirements, Art. III. CR frontage 150 feet. CR accessory buildings: Not stated separately. | 25 feet | 25 feet | 25 feet | 1.0 acre · No base-district limit; 20% impervious in Shoreland Protection Overlay · Height 35 feet |
| LDRLow Density ResidentialTable of Dimensional Requirements, Art. III. LDR frontage 200 feet. LDR accessory buildings: Not stated separately. | 40 feet | 25 feet | 30 feet | 2.0 acres · No base-district limit; 20% impervious in Shoreland Protection Overlay · Height 35 feet |
Verified 2026-11-15 against Zoning Ordinance, Town of Milton, New Hampshire. Towns amend ordinances, so confirm with the land-use office before you build. Official source
FAQ
ADUs in Milton.
- How big can an ADU be in Milton?
- Max 1,000 sq ft (town may not cap below 750 sq ft); max 2 bedrooms; max 4 occupants, per Art. XXI.VI.B.1; III.A as read 2026-11-15.
- Does the owner have to live on the lot in Milton?
- Owner must live in the house or the ADU; only one unit may be rented (Art. XXI.VII.A.2).
- Can an ADU in Milton be detached?
- One per lot; definitions cover attached and detached units, under Art. XXI.III.A-C.
Planning an ADU in Milton?
Call (978) 987-0089 and we will read the ordinance against your lot. See the ADU models