Rockingham County · New Hampshire
ADU rules in Newmarket, NH
Newmarket sits on the Lamprey River and Great Bay in Rockingham County.
This is a reference guide. Newmarket is not on our service-area list, so call to ask whether we can take on a build there.
Town ADU rules
What’s allowed on your lot in Newmarket.
Newmarket allows an ADU with a building permit, renewed every year, between 200 and 1,000 sq ft. The ADU section was last amended in March 2023.
- Size limit
- 200 to 1,000 sq ft gross floor area; no more than 80% of the house, but never capped below 750 sq ft; +100 sq ft bonus for rooftop solar
- Where it can go
- Attached, internal conversion, or detached (in an accessory structure)
- Owner on site
- Owner must live in the house or the ADU (voter or vehicle registration as proof)
- Parking
- On-site parking for both units; no space count in the ADU section
- Approval
- Building permit only; annual ADU recertification
- Rentals
- No short-term rental of the house or the ADU (30 days or less)
- Water setback
- Primary structures 125 ft from the shoreland reference line (Great Bay, Lamprey, Piscassic, Lubberland Creek)
Allowed
- Attached or detachedThree ADU types are defined: attached (AADU), internal conversion inside the house (ICADU), and detached inside an existing or new accessory structure (DADU).§32-11 (definitions)
- OtherADUs are allowed in all districts where single-family residential use exists or is a permitted use.§32-234(a)
- ApprovalAn ADU needs only a building permit, unless state law or the town code says otherwise. Each property with an ADU must file a recertification application every year, or occupancy of the ADU is revoked.§32-234(c), (d)
- Owner on siteThe owner must live in either the house or the ADU as their primary residence, shown by voter or vehicle registration in Newmarket. For trusts and LLCs, a beneficiary must live in one unit.§32-234(e)(1)
- SizeADU must be between 200 and 1,000 sq ft of gross floor area. It cannot be larger than 80% of the house's gross floor area, but that rule cannot cut the cap below 750 sq ft. Maximum two bedrooms. A rooftop solar system on the ADU earns a 100 sq ft bonus.§32-234(e)(2)a., e.
- LotADUs follow the district setbacks in §32-89, except when a legally nonconforming accessory structure is converted. A single-family lot adding an ADU is exempt from the maximum residential density. A lot that adds impervious surface for an ADU may not exceed 65% impervious coverage; above that, stormwater rules apply.§32-234(e)(2)b.-d.
- OtherOn a single-family lot with a manufactured home, only a detached ADU is allowed.§32-234(e)(3)
- DesignAttached and internal ADUs must match the roof pitch, windows, eaves, materials and colors of the house and must not look like a duplex. Exterior stairs to an upper-level ADU cannot face a street. An interior door between the house and the ADU is required (it need not stay unlocked).§32-234(e)(4)a.
- DesignA detached ADU must look like an accessory structure that matches the house. It cannot be closer to the front line than the house, except: the house is 100+ ft back and the ADU is at least 80 ft back; a pre-March 15, 2023 accessory structure is converted; or the ADU is inside a multipurpose accessory structure.§32-234(e)(4)b.
- ParkingOn-site parking must serve both the house and the ADU (no number given). New outdoor ADU spaces may sit inside setbacks if at least 20 ft from a neighbor's dwelling; the Planning Board may cut that to 10 ft by special use permit with screening.§32-234(e)(5)
- SepticAdequate water and sewage disposal are required. Town water/sewer fees are assessed before the building permit. Without town sewer, the septic system must meet NHDES requirements for the combined demand of total occupancy.§32-234(e)(6)
- RentalsShort-term rental of the house, the ADU or both is prohibited. Short-term rental means 30 consecutive days or less, for compensation.§32-234(b)(1); §32-11 (definition)
- ShorelandShoreland Protection Overlay covers land within 250 ft of the reference line of Great Bay, the Lamprey River, Lubberland Creek, the Macallen Dam impoundment and the Piscassic River. RSA 483-B:9 standards apply in full (outside state-exempted parcels), except that the primary structure setback is 125 ft from the reference line (stricter than state). Accessory structures may be 20 ft from the reference line but may have no toilet and may not be used for habitation. Wetland Protection Overlay: prime wetlands 75 ft no-disturbance buffer and 100 ft structure setback; very poorly drained soils 50 ft no-disturbance buffer; poorly drained soils 25 ft buffer.§32-154(c)-(d); §32-155
- State lawThe town text, last amended in 2023, still requires an interior door. State law lets the owner choose how an attached ADU is entered.RSA 674:72, III
Not allowed
- Not allowedShort-term rental (30 days or less) of the house, the ADU or both.§32-234(b)(1)
- Not allowedConverting the ADU to a condominium or separate ownership.§32-234(b)(2)
- Not allowedConverting the ADU into the primary dwelling unless it becomes the only unit on the lot.§32-234(b)(3)
- Not allowedBuilding an ADU in the 100-year flood plain.§32-234(b)(4)
- Not allowedAttached or internal ADU on a lot with a manufactured home (only a detached ADU allowed).§32-234(e)(3)
- Not allowedDesign that makes the house look like a duplex or multifamily building.§32-234(e)(4)a.1.
Read 2026-11-15 from Code of Ordinances, Town of Newmarket, Chapter 32 Zoning (Municode) (§32-234 ADU last amended 'Ord. No. 3-2022/2023, § 2D, 3-1-2023'; §32-89 Dimensions table last amended 'Ord. No. 01-2024/2025, § 2, 6-18-2025'). Anything not listed here, we check with the Newmarket land-use office for your lot.
Setbacks
Front, side and rear in Newmarket.
NH RSA 674:71-73 (HB 577) - one attached or detached ADU by right on a single-family lot
Newmarket's dimensional table, as printed in the ordinance.
| District | Front | Side | Rear | Lot / cover / height |
|---|---|---|---|---|
| VC-NprimaryVillage Corridor North§32-89 Dimensions table; use table §32-56 (single-family excluding mfg. housing: permitted). VC-N frontage 50 ft. VC-N accessory buildings: Accessory sheds (≤120 sf): not listed for VC. | Res. 5 ft min / 20 ft max road setback (comm./mixed-use max 30 ft) | 10 ft | 10 ft | 5,000 sf (0.11 ac) · Not in table (ADU lots: 65% impervious, §32-234(e)(2)d.) · Height 35 ft |
| VC-CVillage Corridor Center§32-89; §32-56. VC-C frontage 40 ft. VC-C accessory buildings: Not specified. | Res. 0 ft min / 20 ft max road setback (comm./mixed-use max 30 ft) | 0 ft | 0 ft | 3,000 sf (0.07 ac) · Not in table · Height 50 ft |
| VC-SVillage Corridor South§32-89; §32-56. VC-S frontage 50 ft. VC-S accessory buildings: Not specified. | Res. 5 ft min / 20 ft max road setback (comm./mixed-use max 30 ft) | 10 ft | 10 ft | 5,000 sf (0.11 ac) · Not in table · Height 50 ft |
| M-2M-2 district§32-89; §32-56; §32-239. M-2 frontage 50 ft. M-2 accessory buildings: Accessory shed ≤120 sf: 5 ft side, 5 ft rear (§32-239). | 10 ft min (max 15 ft) | 10 ft | 10 ft | 10,890 sf (0.25 ac) · Not in table · Height 50 ft |
| M-3M-3 district§32-89; §32-56; §32-239. M-3 frontage 75 ft. M-3 accessory buildings: Accessory shed ≤120 sf: 5 ft side, 5 ft rear (§32-239). | 20 ft min (max 50 ft) | 20 ft | 20 ft | 10,890 sf (0.25 ac) · Not in table · Height 35 ft |
| M-4M-4 district§32-89; §32-56. M-4 frontage 150 ft. M-4 accessory buildings: Not specified. | 20 ft | 25 ft | 25 ft | 43,560 sf (1.00 ac) · Not in table · Height 35 ft |
| B-1B-1 district§32-89; §32-49(b). B-1 frontage 150 ft. B-1 accessory buildings: Not specified. | 15 ft | 25 ft | 25 ft | 21,780 sf (0.50 ac) · Not in table · Height 35 ft |
| R-1R-1 district§32-89; §32-56 (single-family including mfg. housing: permitted). R-1 frontage 200 ft. R-1 accessory buildings: Not specified. | 40 ft | 25 ft | 25 ft | 87,120 sf (2.00 ac) · Not in table · Height 35 ft |
| R-2R-2 district§32-89; §32-56; §32-239. R-2 frontage 100 ft. R-2 accessory buildings: Accessory shed ≤120 sf: 5 ft side, 5 ft rear (§32-239). | 25 ft | 15 ft | 15 ft | 21,780 sf (0.50 ac) · Not in table · Height 35 ft |
| R-3R-3 district§32-89; §32-56; §32-239. R-3 frontage 100 ft. R-3 accessory buildings: Accessory shed ≤120 sf: 5 ft side, 5 ft rear (§32-239). | 25 ft | 15 ft | 15 ft | 21,780 sf (0.50 ac) · Not in table · Height 35 ft |
| R-4R-4 district§32-89; §32-56; §32-239. R-4 frontage 50 ft. R-4 accessory buildings: Accessory shed ≤120 sf: 5 ft side, 5 ft rear (§32-239). | 5 ft | 10 ft | 10 ft | 10,890 sf (0.25 ac) · Not in table · Height 35 ft |
Verified 2026-11-15 against Code of Ordinances, Town of Newmarket, Chapter 32 Zoning (Municode). Towns amend ordinances, so confirm with the land-use office before you build. Official source
FAQ
ADUs in Newmarket.
- How big can an ADU be in Newmarket?
- 200 to 1,000 sq ft gross floor area; no more than 80% of the house, but never capped below 750 sq ft; +100 sq ft bonus for rooftop solar, per §32-234(e)(2)a., e. as read 2026-11-15.
- Does the owner have to live on the lot in Newmarket?
- Owner must live in the house or the ADU (voter or vehicle registration as proof) (§32-234(e)(1)).
- Can an ADU in Newmarket be detached?
- Attached, internal conversion, or detached (in an accessory structure), under §32-11 (definitions).
Planning an ADU in Newmarket?
Call (978) 987-0089 and we will say whether we can build there. See the ADU models