| Max size | 800 sq ftconfirmed with the town |
|---|---|
| Min size | 720 sq ftconfirmed with the town |
| Bedrooms | Up to 2confirmed with the town |
| Type | Attached or detachedgarage conversions allowed |
| Parking | No Requirementconfirmed with the town |
| Owner-occupancy | Requiredin either the ADU or the primary home |
| Short-term rental | Not stated |
| Utility connection | Tie into the existing electrical connection or choose a separate metersame statewide |
The July 2025 state law (RSA 674:71–73) overrides local ordinance language that conflicts with it — even language a town still has posted. Here's what that means in North Hampton:
This is the trap for anyone buying on the Little Boar's Head side of North Hampton. The TOWN of North Hampton's ordinance is now genuinely good — one ADU by right, detached allowed, no extra parking. But Little Boar's Head is a SEPARATE zoning jurisdiction inside North Hampton, with its own Planning Board and its own Zoning Board, and its ordinance is still the 2018 revision. That book is far worse than a single bad clause. It says an ADU is allowed 'only by Special Exception,' that 'Detached accessory dwelling units are prohibited,' that there must be a common wall AND an interior door AND a separate outside entrance, that you must supply TWO off-street parking spaces hidden from the road with no curb cut, and that no more than two people 'unrelated by a familial relationship' may live in the unit. Every one of those is a dead letter under the July 2025 state law: you get one ADU BY RIGHT, attached or DETACHED; you — not the district — choose whether the entrance is separate or shared; the district may demand at most ONE extra parking space and YOU pick whether it is on-site or off-site; and no town may condition an ADU on a family relationship. Two LBH rules DO survive: the 750 sq ft cap on habitable floor area is lawful (it is the lowest maximum state law lets a district set, so it is legal but as tight as legally possible), and the ban on short-term/vacation rental of the ADU is not touched by the ADU statute. The Planning Board finished a rewrite in June 2026 and sent it to the Annual Meeting warrant, but as of July 13, 2026 the voters had NOT yet adopted it, and the district's own website still lists the 2018 Section X as the ordinance 'In Effect.' If your lot is in Little Boar's Head, plan on having to assert state law over the counter, and get the currently-adopted LBH text in writing before you spend a dollar on design.
North Hampton requires any ADU to be at least 720 sq ft on its ground floor. Paired with the 800 sq ft cap, that means every legal ADU in town has to land in a narrow ~720-800 sq ft band — a 400 sq ft studio, a garage-loft apartment, or a tiny-home-scale unit is not permitted by the town's text. State law says nothing about minimum sizes, and it guarantees you an ADU by right; a floor this high arguably guts that guarantee in practice. The town's defense is that it applies the same 720 sq ft floor to EVERY dwelling in town, not just ADUs, which is exactly the 'no requirements beyond a single-family dwelling' test the statute uses. That makes this a genuine gray area — and the single most consequential open question in North Hampton. Get an attorney's read before you design anything under 720 sq ft.
North Hampton's 800 sq ft cap sounds like it clears the state's 750 sq ft floor. It may not. State law measures an ADU by its TOTAL LIVING SPACE and says no town may hold you below 750 sq ft of it. North Hampton instead measures the FOOTPRINT — to the OUTSIDE of the walls — and adds up every floor. Once you subtract exterior wall thickness (and any wall shared with the main house), the actual living space inside a maxed-out 800 sq ft North Hampton footprint lands materially below 800, and plausibly below the 750 sq ft floor the town is not allowed to go under. What the statute measures is NOT in doubt — it is living space, expressly. What IS in doubt is the arithmetic: whether an 800 sq ft footprint, in your specific design, actually drops your living space under 750. Worth an attorney's read if you're designing to the cap, and definitely worth it if you want a two-story unit, since the second floor eats your allowance rather than doubling it.
State law lets a town say 'no ADU' on a lot with multiple single-family homes that are attached to each other — townhouses. North Hampton's §401.4 goes further and also excludes lots with multiple single-family homes that are NOT attached. That extension isn't in the statute's grant of authority. It's a narrow situation — most lots have exactly one house — but if your lot legally holds two separate detached houses, the town's flat 'not eligible' is on shaky ground and is worth pushing back on.
CONFIRMED WITH THE TOWN (July 29,2026) — ADUs allowed: 1; maximum size 800 sq ft; minimum size 720 sq ft; up to 2 bedrooms; impact fees: No; parking: No Requirement; detached-unit distance rule: No regs for a min or max distance from existing structure; setbacks: Side and rear both 15ft Biggest distrect is R1 with smaller lots and R2 with larger lots.. Town contact: Jared shaheen - Building Inspector.
Building window is extremly tight going from 720- 800 sqft, They said setbacks would change or could be adjusted based off what district the ADU is being built in.
Town was uses most of its regular building regulations for their adus and refers back to them, Not to many ADU specific regulations outside of size.
North Hampton is one of the good ones. On March 10, 2026, town voters passed Warrant Article Four — a full rewrite of Zoning Ordinance Section 401 and the Section 104 definitions — explicitly to bring the town into conformance with the new state ADU law (RSA 674:71-73, as amended by HB 577, effective July 1, 2025). The Planning Board had recommended it 5-0 after working it through a dedicated ADU Ad Hoc Committee, and the town has already republished its consolidated zoning ordinance with a 'March 10, 2026' header, so the posted PDF you'll find on the town website IS the current law, not a stale copy.
What you get in North Hampton today: ONE accessory dwelling unit per single-family home, BY RIGHT. Not a special exception, not a conditional use permit, not a Planning Board hearing — you pull a building permit from the Building Inspector and go (Section 401.3). It can be inside the house, attached to it, or fully detached (401.6). You can convert an existing structure — an old garage, say — even if that structure violates today's setback or lot-coverage rules, as long as it legally existed on or before July 1, 2025 (401.12). You can build the ADU at the same time as a brand-new house (401.1). For an attached unit, YOU choose whether the entrance is separate or shared through the main house (401.9). Up to two bedrooms (401.10). You or a family member must live in one of the two units, but the town doesn't care which (401.13). Height is the ordinary 35 feet, setbacks are the ordinary district setbacks — an ADU is held to the same dimensional rules as a regular house, no stricter (401.11, 203.13). And notably, North Hampton requires NO extra parking space for an ADU at all — the state would have let it demand one, and it didn't. The only durable string attached is that you can't later split the ADU off and sell it as a condo (401.14), and you have to show the Building Inspector your well and septic can handle both units (401.15). One eligibility gate to know about up front: if you LEASE the land under your home rather than own it (a ground lease, or a manufactured-housing park), Section 401.2 says no ADU — and that exclusion is one the state law expressly lets a town make (RSA 674:72, I), so there's no state-law argument to make against it.
So where's the catch? Two places.
FIRST — THE SIZE SQUEEZE. North Hampton caps an ADU at an 800 square foot FOOTPRINT (401.7), and 'footprint' here is measured to the OUTSIDE of the walls, with every floor's footprint added together against that single 800 number. A two-story ADU doesn't get 800 per floor — it gets 400 each. Then, separately, Section 401.8 sets a MINIMUM: any ADU must have at least 720 square feet of ground-floor living area. That's a real minimum, and it's unusual. Put the two rules side by side and every legal ADU in North Hampton has to land in a narrow band of roughly 720 to 800 square feet. The 400 square foot backyard cottage, the garage-loft studio, the tiny-home-scale unit — the town's text does not permit them. State law says a town may cap an ADU's size but never below 750 sq ft; it says nothing at all about a minimum, and it bars towns from loading requirements onto an ADU beyond what they'd require of a regular house. The town's answer is that its 720 sq ft floor comes straight from Section 203.14, a 1976 rule that applies to EVERY dwelling unit in North Hampton, not just ADUs — which is arguably exactly the equal-treatment test the statute uses. That makes this a genuine legal gray area rather than a slam-dunk override, and it's the single most important thing to get an attorney's read on before you design. There's a related wrinkle: because the 800 sq ft cap is measured to the outside of the walls, the actual interior living space of a maxed-out unit can land under 750 sq ft — below the floor state law says a town may hold you to. And on this point the statute is NOT ambiguous: RSA 674:72, VII measures an ADU by its 'total living space,' expressly, and says a municipality 'may not restrict the total living space to less than 750 square feet.' North Hampton is measuring something the statute doesn't measure. The open question is purely arithmetic — whether, in your specific design, an 800 sq ft exterior footprint actually leaves you under 750 sq ft of living space. (Worth watching: the Planning Board was still discussing ADU living-area regulations in its March 17 and April 21, 2026 work sessions, after the ballot passed — so this may get amended again.)
SECOND — LITTLE BOAR'S HEAD. This is the one that will blindside people, and it is worse than a single stale clause. The Village District of Little Boar's Head is a separate zoning jurisdiction inside North Hampton, covering the coastal section, with its OWN Planning Board and its OWN Zoning Board. Its operative ordinance is still the 2018 revision, and its Section X is out of step with the state law in six different places at once. It says an ADU is 'permitted only by Special Exception.' It says 'Detached accessory dwelling units are prohibited' and that there must be a 'common wall' with the main house — which also forecloses the detached-garage conversion the state law expressly guarantees. It requires BOTH an interior door between the units AND an independent outside entrance, taking away the choice the statute hands to you. It demands TWO off-street parking spaces, 'not visible from the road' and with no curb cut — where the state lets a district require at most ONE additional space and lets YOU decide whether it sits on-site or off-site. And it caps occupancy at two people 'unrelated by a familial relationship,' when the state flatly bars any familial-relationship condition on an ADU. Every one of those is a dead letter under the July 2025 law — but you will be arguing state law across the counter to a village board reading from a book that hasn't been fixed yet. Two LBH rules DO hold up, so don't over-read this: its 750 sq ft cap on habitable floor area is legal (750 is the tightest maximum the state allows a district to set — legal, but as tight as legally possible), and its ban on renting the ADU as a short-term/vacation rental is untouched by the ADU statute. The LBH Planning Board did finish a compliant rewrite in June 2026 and sent it to the Annual Meeting warrant — but as of July 13, 2026 the VOTERS HAD NOT YET ADOPTED IT, and the district's own website still lists the 2018 Section X as the ordinance 'In Effect.' If your property is in Little Boar's Head rather than plain North Hampton, treat the town's excellent Section 401 as NOT applying to you, check whether the Annual Meeting has since passed the rewrite, and get the currently-adopted LBH text in writing before you spend a dollar on design.
Bottom line: in ordinary North Hampton, an ADU is genuinely easy — by right, detached allowed, no extra parking, no ZBA. Just don't plan on building a small one, and make sure you know which side of the Little Boar's Head line you're on.
Primary source: Town zoning ordinance (PDF) — §401 last amended March 10, 2026
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Get My Free North Hampton ADU Report →House Bill 577 (2025) amended RSA 674:72, effective July 1, 2025. Wherever North Hampton's ordinance is stricter than this floor, the state law controls. Read the full NH ADU law explainer →
Yes — North Hampton allows one accessory dwelling unit, attached OR detached, BY RIGHT with just a building permit, in every district that allows single-family homes (R-1, R-2, I-B/R). Under RSA 674:72 (as amended effective July 1, 2025), one accessory dwelling unit — attached or detached — is allowed by right on single-family lots statewide.
800 sq ft — confirmed with the town. State law doesn't let any town cap ADU size below 750 sq ft.
Attached or detached (garage conversions allowed). Since July 1, 2025, state law allows detached ADUs by right statewide — town provisions that prohibited them are superseded.
No Requirement — confirmed with the town. State law caps what any town can require at one additional space, located on- or off-site at the owner's choice.
Required — in either the ADU or the primary home. Where owner-occupancy is required, state law lets the owner choose which unit to live in.