Can My Town Say No to a Detached ADU? What NH Law Actually Allows in 2026

No — your town cannot say no to a detached ADU. Under RSA 674:72 (amended by House Bill 577, 2025 Chapter 197, effective July 1, 2025), every New Hampshire municipality must allow one accessory dwelling unit — attached or detached — by right wherever single-family homes are permitted, with no special exception, variance, or conditional-use permit for the ADU itself.

That's the short answer. The longer answer is that plenty of town ordinances, town websites, and counter conversations still say no, because the local paperwork hasn't caught up to the state law. This article covers what "by right" actually means, the short list of things your town can still legitimately regulate, and what to do when someone at the permitting counter quotes an ordinance the state has already overridden.

What does "allowed by right" mean for a detached ADU?

"By right" means the use itself is not up for debate. You don't ask the zoning board for permission to have a detached ADU; you apply for a building permit the same way you would for any addition. What still applies:

• A normal building permit and inspections.
• Reasonable local standards: setbacks, lot coverage, septic capacity, building and fire codes.
• A town size cap, if it has one — but the cap can never be set below 750 sq ft.
• Owner-occupancy of the property, if the town requires it — though you pick which unit you live in.
• At most one additional parking space — and you choose whether it goes on-site or at a legally dedicated off-site location.

What no longer applies, anywhere in New Hampshire: a hearing to decide whether your detached ADU can exist. The full statewide picture is on our NH ADU law page.

What can't my town require anymore?

Beyond banning detached units outright, several once-common ordinance conditions are now off the table statewide. A town cannot:

• Require the ADU occupant to be a family member.
• Limit the unit to one bedroom.
• Force the ADU to share the main home's electrical service — a separate connection or meter is the owner's choice.
• Block you from converting an existing garage into an ADU just because the garage doesn't meet today's setbacks.
• Demand more than one extra parking space, or dictate that it must be on your lot.

If an ordinance clause on any of these points predates — or simply ignores — the 2025 law, state law controls.

Why does the town office still say no?

Zoning ordinances get amended at town meeting, usually once a year, and many towns haven't reconciled their posted text with RSA 674:72. Some towns have even amended their ADU sections since the law took effect and still kept conflicting language. Real examples from our town-by-town review:

• Candia's ordinance carries a 2026 revision date, yet still requires every ADU to share the main house's street entrance and mandates on-site-only parking — both overridden by state law.
• Hollis revised its zoning ordinance in April 2026 and still requires a lot to be double the district's minimum size before a detached ADU is even eligible, and still routes ADUs in one district through a special-exception hearing. State law overrides both.
• In North Hampton, the town itself passed a genuinely compliant rewrite in March 2026 — but the Little Boar's Head village district inside the town is a separate zoning jurisdiction whose posted ordinance still says detached ADUs are prohibited and ADUs are allowed only by special exception. As of this site's most recent check, its replacement ordinance had not yet been adopted by voters, so a homeowner there should expect to assert state law at the counter.

None of this means those towns can actually stop your project. It means the person behind the counter may be reading from a book the legislature has already rewritten. Not every town is behind, either: Atkinson proactively aligned its ordinance with the state law and even allows ADUs up to 1,000 sq ft — more generous than many towns.

What should I say at the counter when the clerk quotes the old ordinance?

Stay friendly. The clerk didn't write the ordinance, and in most towns the staff genuinely wants to get it right. A script that works:

1. Ask for the specific citation. "Which section of the ordinance are you relying on, and when was it last amended?" This turns a vague "we don't allow those" into a checkable claim.
2. Name the statute. "My understanding is that RSA 674:72, effective July 1, 2025, allows one ADU — attached or detached — by right wherever single-family homes are permitted. Can you tell me how the town reads that against this section?"
3. Bring the ordinance and the statute side by side. Every town guide on this site does exactly this reconciliation — which clauses of the local ordinance stand, and which are superseded. Print your town's page or pull it up on your phone.
4. Ask for any denial in writing. "If the town's position is that a detached ADU isn't permitted here, could I get that in writing with the ordinance citation?" Verbal no's tend to soften when they have to become written ones — and if you do get a written denial, it's exactly what a land-use attorney needs to resolve things quickly.
5. Concede what the town legitimately controls. Make clear you fully expect to meet setbacks, septic requirements, building code, and any lawful size cap. You're not asking for an exception; you're asking for the by-right process the statute requires.

One caution: don't treat the statute as a magic word that ends every conversation. Towns still have real authority over the details, and a genuinely gray question — say, how a town-wide dimensional rule interacts with the ADU statute — is a question for a New Hampshire land-use attorney, not a counter argument.

How do I find out what my specific town says?

Start with your town's page — our town guides read each ordinance clause-by-clause against RSA 674:72 and flag every spot where the posted local rule is superseded. If you're in the Seacoast area, the Rockingham County guide is a good entry point, since several of the sharpest ordinance-versus-statute conflicts we've found sit there. Where a town's numbers carry the verified badge, they've been confirmed directly with the town office.

The state has already answered the question in the title — your job isn't to win the argument, it's to show up knowing it's settled.