| Max size | 1,000 sq ftor 50% of main house, whichever less |
|---|---|
| Min size | No town minimum750 sq ft floor protects you |
| Bedrooms | Up to 2 |
| Type | Attached by rightdetached: special exception, conversion |
| Parking | 1 spaceordinance says on your own lot |
| 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 Andover:
Since July 2025, state law entitles you to build one detached ADU — a garage apartment or standalone cottage, for example — without any board hearing at all. Andover's ordinance still says a homeowner must go before the Zoning Board of Adjustment and win a Special Exception for a detached ADU, but that requirement is now superseded. This is Andover's single biggest ADU rule that state law overrides.
In Andover's Forest & Agriculture district, the ordinance offers no detached-ADU pathway at all — not even with a hearing. Whether the FA district's own special-exception treatment of single-family homes changes how the state mandate applies there is a genuine legal question, but a flat, district-wide detached-ADU ban is a strong candidate for being overridden by state law.
State law doesn't limit your detached ADU to conversions of existing buildings. Andover's rule that you can only turn an EXISTING building (like a garage) into a detached ADU — never build a brand-new freestanding one — is a town-only restriction that is likely no longer enforceable.
Under state law, the choice between an on-site space and a legally dedicated off-site spot belongs to you. Andover can require the extra parking space (its general residential parking rule already applies to every home), but its on-your-own-lot-only requirement is overridden.
State law says the choice of where the ADU's entrance goes — including a separate front door — belongs to the homeowner, not the town. Andover's ordinance still flatly bans a separate front entrance except by winning a hardship-style Special Exception for handicap access, but that restriction no longer controls.
State law doesn't allow ADU-specific lot-size gating. Andover's ordinance still lets the Board of Adjustment tack on its own minimum lot size or frontage as a condition of approving a detached ADU — on top of, or instead of, the ordinary district minimums — but that authority is superseded.
Andover can only hold your ADU to the same look-and-feel standards it holds any house to — not a vaguer, ADU-specific 'rural character' standard. Whether this clause crosses that line is an attorney call.
Start with the state-law baseline: since July 1, 2025, New Hampshire law (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 permitted, with no special exception or board hearing for that one by-right unit, at most one added parking space (on-site or off-site, your choice), and no town-dictated entrance location. Andover's Accessory Dwelling Unit ordinance (Zoning Article XV) is a genuinely thorough, ADU-dedicated article — but it was last amended at Town Meeting in March 2017 and hasn't been revisited since, leaving it out of step with that state floor in several material ways. What's already consistent with state law: one ADU per single-family lot, attached ADUs are a by-right accessory use with no board hearing, owner-occupancy is required in either unit (town doesn't say which), max two bedrooms, size caps of up to 1,000 sq ft (more generous than the state's default 950 sq ft ceiling, which is allowed), and no minimum size is actually imposed. Where the town's stale text is now overridden by state law: (1) the ordinance still says a DETACHED ADU requires winning a Special Exception from the Zoning Board of Adjustment — state law now entitles homeowners to one detached ADU by right, no hearing required; (2) the ordinance offers no detached-ADU pathway at all in the Forest & Agriculture District; (3) even where allowed, the ordinance limits a detached ADU to conversion of an existing structure — 'no new structure shall be built for the principal purpose of constructing a detached ADU' — a restriction state law doesn't authorize; (4) the ordinance says the required parking space must stay on your own lot, but state law gives homeowners the on-site/off-site choice; (5) the ordinance restricts the ADU's entrance to the side or rear of the building (a front entrance needs its own hardship-style Special Exception, even for handicap access) — state law bars towns from dictating ingress/egress choice like this; (6) the ordinance lets the Board of Adjustment impose its own minimum lot size or frontage as a condition of approving a detached ADU, which state law doesn't permit; and (7) a vague 'rural character' aesthetic-consistency clause may exceed what state law allows (attorney call). See the conflicts list for full citations. Andover has not yet updated any of these provisions since the state law changed, so where the two disagree, the state law is the operative rule.
Get a free personalized report for your address in Andover — including where the 2025 law works in your favor.
Get My Free Andover ADU Report →House Bill 577 (2025) amended RSA 674:72, effective July 1, 2025. Wherever Andover's ordinance is stricter than this floor, the state law controls. Read the full NH ADU law explainer →
Yes — and under the 2025 state law you're entitled to one ADU by right whether it's attached OR detached. Andover's ordinance still says a detached ADU needs a Special Exception hearing before the Zoning Board of Adjustment, but state law now overrides that. 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 — or 50% of main house, whichever less. State law doesn't let any town cap ADU size below 750 sq ft.
Attached by right (detached: special exception, conversion). Since July 1, 2025, state law allows detached ADUs by right statewide — town provisions that prohibited them are superseded.
1 space — ordinance says on your own lot. 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.