| Max size | 950 sq ftconfirmed with the town |
|---|---|
| Min size | No town minimumbuild as small as code allows |
| Bedrooms | Up to 2confirmed with the town |
| Type | Attached or detachedyour choice |
| Parking | Adequate parking for both ADU and PDUconfirmed 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 Hampstead:
State law is the operative rule here: as of July 1, 2025, a homeowner is entitled to build one ADU by right — no special exception or board hearing — regardless of whether the underlying lot is legally nonconforming. Town staff have described an acreage-based special-exception gate for lots under about an acre; if that gate is being applied to block or delay ADU approvals, it is very likely superseded. IMPORTANT CAVEAT: this gate was described verbally and does not appear in the written ADU guidelines — it may be a general dimensional-nonconformity procedure that predates the 2025 law and applies to all construction, not an ADU-specific rule. Get the town's position in writing (ask for the ordinance section, not just a verbal description) and consider an attorney's read before relying on it.
State law says you may convert an existing structure — including a detached garage — into an ADU even where it is setback- or lot-coverage-nonconforming. Hampstead's guidelines don't contradict that; they simply don't address it. Because the town's document is silent rather than contradictory, treat this as a point to confirm with the Building Department, not a confirmed violation.
CONFIRMED WITH THE TOWN (August 12, 2026) — ADUs allowed: 1; maximum size 950 sq ft; up to 2 bedrooms; impact fees: None; parking: Adequate parking for both ADU and PDU; detached-unit distance rule: No; setbacks: Residential Zone A/Recreational Zone B 50 Rear, 30 Front/Side. Town contact: Debbie Soucy - Planning 603-329-4100 Ext. 102.
ADUs are only allowed in Residential Zone A and Recreational Zone B.
Pat confirmed requirments on August 12, 2026
Start with your rights under state law: since July 1, 2025, RSA 674:71-73 (as amended by HB 577) entitles you to one accessory dwelling unit — attached or detached — by right wherever single-family homes are allowed, with no special exception or board hearing. Hampstead's Building and Code Enforcement Department's "Accessory Dwelling Unit Guidelines as of 7/1/2025" — dated to the exact day the amended law took effect — largely line up with that: one ADU per lot (attached or detached, no CUP or special exception mentioned for the ADU itself), processed through a Minor Building Permit application with architectural plans, capped at 950 sq ft and two bedrooms, with mandatory owner-occupancy of either unit (evidenced and certified), a well/water-adequacy check, RSA 485-A sewage disposal approval, a certification recorded in the Rockingham County Registry of Deeds, and a ban on condominium conveyance of either unit. Formal town-wide adoption of the updated zoning package is expected at the March 2026 Town Meeting, but the Building Department is already applying these guidelines in practice. The one real watch-item isn't in the written guidelines: town staff have stated that lots under roughly one acre are treated as legally nonconforming and require a special exception permit from the Zoning Board before construction can proceed. If that acreage gate is applied to ADUs specifically, the state law's by-right mandate very likely overrides it — but get the town's position in writing (a verbal description is not a cited ordinance section), and consider an attorney's read before relying on it. Separately, the guidelines don't say whether converting an existing, setback-nonconforming detached structure (like a garage) into an ADU is exempt from that nonconformity — state law says it must be allowed, but the town's silence is a gap to confirm, not a confirmed violation. Parking, height, and short-term-rental rules for ADUs are not addressed in the guidelines — confirm those directly with the Building Department (603-329-4100).
Get a free personalized report for your address in Hampstead — including where the 2025 law works in your favor.
Get My Free Hampstead ADU Report →House Bill 577 (2025) amended RSA 674:72, effective July 1, 2025. Wherever Hampstead's ordinance is stricter than this floor, the state law controls. Read the full NH ADU law explainer →
Yes — Hampstead allows one accessory dwelling unit (attached or detached) by right via a Minor Building Permit, in line with the state's July 1, 2025 by-right ADU law. 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.
950 sq ft — confirmed with the town. State law doesn't let any town cap ADU size below 750 sq ft.
Attached or detached (your choice). Since July 1, 2025, state law allows detached ADUs by right statewide — town provisions that prohibited them are superseded.
Adequate parking for both ADU and PDU — 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.