| Max size | 1,000 sq ftconfirmed with the town |
|---|---|
| Min size | Noconfirmed with the town |
| Bedrooms | Up to 2confirmed with the town |
| Type | Attached or detacheddetached tightly gated; CUP-superseded |
| Parking | 1 spot 9'x18' minimumconfirmed with the town |
| Owner-occupancy | Requiredin either the ADU or the primary home |
| Short-term rental | 6-month minimum rentalde facto short-term rental ban |
| 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 Hampton:
State law is the operative rule: as of July 2025, you are entitled to build one ADU by right — no CUP hearing required. Hampton's posted ordinance still routes every ADU through a Planning Board Conditional Use Permit hearing with abutter notice, but that requirement is superseded — it's the single biggest thing Hampton's ordinance gets wrong relative to current law.
State law entitles you to a detached ADU up to the state's size band (750-950 sq ft; the town's stated cap here is 800 sq ft) without a CUP hearing. Hampton's rule that a NEW detached ADU can't exceed 5% of your lot — and that a converted pre-2024 shed/garage can't be made one inch bigger — is exactly the kind of restriction the 2025 law was written to override.
State law says the entrance choice — shared interior or separate exterior — is yours, not the town's. Hampton's ordinance still reads as if an attached ADU must share an interior door with the main house, but that requirement no longer controls.
State law lets Hampton require one extra parking space at most — and gives you the choice of a legally-dedicated off-site spot instead of your own lot. The town's on-site-only rule cannot take that choice away.
State law says an ADU may be built at the same time as the principal home. Hampton's ordinance doesn't explicitly forbid that, but its language and application form assume the house already exists. Whether the town would actually block a same-time build is untested — worth a direct call to the Planning Office before assuming either way.
State law says Hampton can only hold your ADU to the same design standards it holds a regular home addition to — not stricter ones. Whether the specific roofline-mirroring and no-new-curb-cut rules cross that line is a case-by-case call, best made with a NH land-use attorney.
CONFIRMED WITH THE TOWN (August 12, 2026) — ADUs allowed: 1; maximum size 1,000 sq ft; minimum size No; up to 2 bedrooms; impact fees: Only required for 2 bedroom ADU's -$2485; parking: 1 spot 9'x18' minimum; detached-unit distance rule: If detached, it will need to be at least 7 feet away from the existing structure.; setbacks: Residential A zone (most common) 20 front 15 side 10 rear. Town contact: Jason Bachand town planner 603-929-5913.
Residence B zoning = 25% max impervious surface coverage, unless the lot is under half an acre, then the impervious surface coverage goes to 40%. Check wetlands! They have a 50 ft buffer PLUS 12 foot dwelling unit setback from that. Even if wetlands look like a non-issue, give the conservation coordinator a call to triple check.If homeowner is in a zone that allows duplexes (like residence B), it DOES need to be attached to be considered a duplex. Definition says “under one roof”, and each unit must be at least 500sqft. Check with building inspector very early on to see if a survey will be required.
Pat confirmed requirments on August 12, 2026
Start with what state law guarantees you (effective July 2025): one ADU by right — attached or detached — in every district that allows single-family homes, with no Conditional Use Permit or Planning Board hearing; a detached ADU as a protected option; entrance choice in your hands; and at most one extra parking space, which you may place on-site or at a legally dedicated off-site location. Now, what Hampton's posted ordinance still says: one ADU (attached or detached) per single-family lot, capped at 800 sq ft and 2 bedrooms, with the owner required to live in either unit and a minimum 6-month rental term (no short-term rentals). Detached ADUs are tightly restricted — a pre-2024 structure can be converted but never enlarged, and a brand-new detached structure is capped at 5% of your total lot area. Every ADU — attached or detached — currently requires a full Conditional Use Permit hearing before the Planning Board (abutter notice, 8 sets of plans, a pre-application questionnaire) plus a Building Permit. One extra on-site parking space is required, and an impact fee equal to a two-unit-structure fee applies with no waiver allowed. A recorded deed covenant (RA/RAA zones only) requires the property to revert to single-family use if owner-occupancy lapses. Where the two collide, state law wins: (1) you do NOT need a Conditional Use Permit or Planning Board hearing for a single ADU — RSA 674:72 makes it by-right in every zone that allows single-family homes, which in Hampton is every residential district; (2) a detached ADU is your right too — not something the town can cap at 5% of your lot or forbid enlarging; the state sets the size band at 750-950 sq ft regardless of the town's percentage rule; (3) the town cannot force a shared interior door between your house and the ADU — you can choose a separate exterior entrance; (4) the town can require one parking space, but you can put it off-site if you'd rather not use your own lot. The owner-occupancy requirement, by contrast, is a rule towns may still lawfully impose (though the town cannot dictate which unit you live in). Two items remain genuinely unclear and worth a direct call to the Planning Office or a NH land-use attorney: whether Hampton would object to building the ADU at the same time as a brand-new home, and whether the roofline-mirroring/design-continuity rule goes further than what's allowed for a regular home addition. Bottom line: Hampton's ordinance predates the current law by more than a year, and the town may already be revising it — planning staff have mentioned a possible March 2026 amendment raising the detached cap to 1,000 sq ft — but that revision is unconfirmed, so don't rely on it. Call Jason Bachand at the Planning Office (603-929-5913) to confirm the live rules before you file anything.
Get a free personalized report for your address in Hampton — including where the 2025 law works in your favor.
Get My Free Hampton ADU Report →House Bill 577 (2025) amended RSA 674:72, effective July 1, 2025. Wherever Hampton's ordinance is stricter than this floor, the state law controls. Read the full NH ADU law explainer →
Yes — state law entitles you to one accessory dwelling unit, attached or detached, by right on any Hampton lot with a single-family home. The town's posted ordinance still runs every ADU through a Planning Board Conditional Use Permit hearing — a requirement state law eliminated in July 2025. 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.
1,000 sq ft — confirmed with the town. State law doesn't let any town cap ADU size below 750 sq ft.
Attached or detached (detached tightly gated; CUP-superseded). Since July 1, 2025, state law allows detached ADUs by right statewide — town provisions that prohibited them are superseded.
1 spot 9'x18' minimum — 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.