Several New Hampshire towns' posted zoning ordinances still tell homeowners that a detached ADU is prohibited, special-exception-only, or hemmed in by rules the state has since outlawed — and those clauses no longer control. Since July 1, 2025, state law (RSA 674:72, amended by House Bill 577, 2025 Chapter 197) allows one ADU, attached or detached, by right wherever single-family homes are permitted, and where a local ordinance conflicts with that law, the state law wins.
This isn't a technicality. It's the difference between a counter clerk telling you "detached units aren't allowed here" and you actually having the right to build one. Below are real examples from our town-by-town review — including ordinances amended after the state law took effect that still carry superseded language.
New Hampshire towns amend zoning at town meeting, usually once a year. When the state's ADU law changed effective July 1, 2025, every local ADU ordinance in the state was instantly measured against a new floor: one ADU by right (attached or detached), no special exception or variance for the ADU itself, size caps no lower than 750 sq ft, at most one extra parking space (owner's choice of on-site or off-site), no family-member requirement, no one-bedroom limit, and garage conversions allowed even where the garage doesn't meet current setbacks.
A conflicting local clause doesn't have to be repealed to stop working. State statutes sit above local ordinances, so a town rule that contradicts RSA 674:72 is unenforceable the moment the statute takes effect — whether or not the town ever gets around to editing its PDF. But here's the trap: the posted ordinance is what the town website shows you, what the building department hands you, and often what gets quoted at the permit counter. Unless you know which clauses are superseded, you'll walk away believing rules that no longer bind you.
These examples come straight from the current posted ordinances we reviewed for our town guides. None of these towns is doing anything unusual — that's the point. Stale clauses are the norm, not the exception.
Candia's zoning ordinance is literally titled a "2026 Revision," with an amendment history running through March 10, 2026 — months after the state law took effect, with a full town-meeting cycle in between. To its credit, Candia does allow one ADU (attached or detached) by right in its residential and mixed-use districts. But the ADU section still requires every ADU to use the existing entrance from the street and share it with the primary dwelling, still requires ADU parking to be provided on-site under a schedule that appears to call for more than one space, and still contains no exemption letting you convert an existing detached garage that doesn't meet today's setbacks — a conversion the state law explicitly protects. The ordinance also requires any detached unit to sit within 100 feet of the primary dwelling, which could complicate converting a legitimately existing outbuilding sited farther away. A homeowner reading Candia's posted ordinance at face value would design a fundamentally different (and more constrained) project than the one state law entitles them to.
Hollis recodified its zoning ordinance in May 2025 and revised it again on April 8, 2026 — and its ADU chapter even says it's meant to be consistent with RSA 674:72. Much of it genuinely is, and the town's numbers have been confirmed directly with the town office. But the ordinance still says detached ADUs are "only allowable" on a lot with double the district's minimum lot size — which in the town's main residential districts, where an ordinary house needs 2 acres, means a 4-acre lot before a detached ADU is even eligible. State law makes one detached ADU a by-right use wherever single-family homes are allowed; it doesn't let a town admit detached units in principle while pricing most lots out of eligibility through an acreage gate. Hollis also still routes ADUs in its Water Supply Conservation district through a special-exception hearing, even though single-family homes are permitted there by right — exactly the discretionary approval the state law removed. This is a Hillsborough County town whose ordinance was revised as recently as April 2026 — well after the law took effect — and both clauses are still on the books.
North Hampton is actually the success story. In March 2026, town voters passed a full rewrite of their ADU ordinance specifically to conform to the state law: one ADU by right with just a building permit, detached units expressly allowed, garage conversions protected even where the structure doesn't meet current setbacks, and no extra parking requirement at all. Those details are confirmed with the town.
The trap is geographic. The Village District of Little Boar's Head — a separate zoning jurisdiction covering the coastal portion of North Hampton, with its own boards — still operates under an older ordinance whose ADU section says an ADU is permitted only by special exception and that detached accessory dwelling units are prohibited outright. It also demands two off-street parking spaces and restricts who may occupy the unit based on family relationship — all of it the kind of language the 2025 state law was written to override. A replacement ordinance has been drafted, but as of this site's most recent review in July 2026 it had not yet been adopted, and the district's own materials still list the older text as the ordinance in effect. If your lot is on the Little Boar's Head side of this Rockingham County town, the posted rules and your actual rights are two very different documents.
The ordinance on the town website is a snapshot. The law is the law — and since July 1, 2025, the law says one detached ADU is yours by right, no matter what the town's PDF says.
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