| Max size | 1,000 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 detachedgarage conversions allowed |
| Parking | No requirementconfirmed with the town |
| Owner-occupancy | Requiredin either the ADU or the primary home |
| Short-term rental | Not statedrenting is expressly allowed |
| 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 Plaistow:
Plaistow's ADU article is written as if you already own a house and are adding a unit to it. If you're building a brand-new home in Plaistow, state law says you can build the ADU in the same project — you don't have to finish the house first and come back later. If the Building Department pushes back on a combined permit, this is the statute to cite.
Plaistow requires the ADU and the main house to share ONE driveway entrance onto the street. A single-curb-cut rule is a fairly ordinary town-wide driveway/traffic standard, and if Plaistow applies it to any lot it is probably lawful parity. The place it gets shaky is a pre-existing detached garage that already has its own drive: state law says the town must let you convert that garage even when it doesn't conform. Genuine gray area — raise an existing second curb cut with the town early. Do not expect the 'ingress and egress' sentence in the statute to help you: that sentence is about which DOOR an attached unit uses, not driveways.
If your principal home is a manufactured/mobile home ON LAND YOU OWN, Plaistow's ordinance says flatly that you can't add an ADU — and the state ADU law creates no such exception (it lists the exclusions a town may make, and mobile homes aren't among them), while NH separately protects manufactured housing that qualifies as a single-family dwelling. That is a real question mark worth an attorney's time. BUT if your home sits on a LEASED park lot, the town can lawfully say no on that basis alone — state law expressly lets a municipality prohibit ADUs on rented or leased land. Owning the ground under your home is what unlocks this argument.
Before you can even file your septic design with the State (NHDES), Plaistow requires you to dig a test pit and have the Town Health Officer physically there to witness it, and to have the town review your design first. That is a real cost and schedule gate — you're waiting on a town official's calendar before the state clock even starts. State law says the town may not impose GREATER septic requirements on a house-plus-ADU than NHDES itself requires, and NHDES does not require a town-witnessed pit. Whether Plaistow's extra step survives that sentence has not been tested. Worth raising if the scheduling is holding up your project; not a reason to walk away.
Read literally, §220-35 could be used to argue that a DETACHED ADU is a second 'Structure containing Dwelling Units' and therefore doubles the lot size you need (e.g. 80,000 sq ft in MDR instead of 40,000). That reading would gut the detached-ADU right the state just granted. The better reading is that §220-35 applies only to multiple PRINCIPAL uses, and an ADU is by definition an ACCESSORY use — so it shouldn't apply. Article VIII itself imposes no lot-size gate at all. This is an ambiguity a reviewer/attorney should resolve, not a settled conflict; nothing in the town's own plain-English ADU guidance mentions any extra lot-size requirement.
CONFIRMED WITH THE TOWN (August 27,2026) — ADUs allowed: 1; maximum size 1,000 sq ft; up to 2 bedrooms; impact fees: School Impact fee-$1.72/SF, Recreation Impact fee-$0.48/SF, Public Safety Impact Fee-$1.04/SF; parking: No requirement; detached-unit distance rule: No; setbacks: Medium Density Residential. 35’Front, side/rear 15’. Lower density 25’ side and rear. Town contact: Shea - Planning department.
Slow to none response time when leaving voicemails. Closed Fridays
Pat called town hall on August 14 but were closed. Pat called August 19,2026 with no answer and left 2 voicemails to the planning department and to the Building inspector. Varified August 27, 2026
Plaistow is a good-news town. At the March 10, 2026 town meeting, voters adopted Zoning Amendment Z-26-8, which rewrote Article VIII (Accessory Dwelling Units) of the zoning ordinance from top to bottom to line up with the new state ADU law (RSA 674:71-73, as amended by HB 577, effective July 1, 2025). The rewritten section now literally opens with the words 'In accordance with RSA 674:71 through RSA 674:73.'
WHAT YOU GET IN PLAISTOW: • ONE ADU per lot, ATTACHED OR DETACHED, permitted BY RIGHT in every district that allows single-family homes (MDR, LDR, RC1, RC2, ICR, and residential lots in VC and C2). 'By right' is the whole ballgame: no special exception, no conditional use permit, no Zoning Board or Planning Board hearing. You go to the Department of Building Safety, pull a building permit, and build. (Ignore any third-party ADU website still telling you Plaistow requires a Conditional Use Permit — that is out of date.) • UP TO 1,000 SQUARE FEET. That's MORE than state law would have let the town cap you at (the state floor is 750 and its default is 950). Plaistow chose to be generous. There is no 'percentage of your main house' formula to shrink you. • TWO BEDROOMS. Allowed outright. • DETACHED GARAGE CONVERSIONS ARE EXPRESSLY BLESSED — including where the garage is already too close to the property line. The ordinance says conversions of structures that existed before July 1, 2025 are allowed 'regardless of whether such Structures violate current dimensional requirements for setbacks and/or Lot Coverage.' This is the single most valuable clause in Plaistow's ordinance and many towns still don't have it. ONE ASTERISK: Plaistow bolted a July 1, 2025 cutoff onto that carve-out. The state version (RSA 674:72, XI) has NO cutoff date — it protects conversions of 'existing structures' full stop. In practice this rarely bites, because a structure built after July 1, 2025 would normally have been built conforming anyway; but if you have a post-2025 outbuilding that is nonconforming for some reason, the state text is broader than the town's. • NO EXTRA PARKING SPACE REQUIRED. Article VIII imposes no parking-count at all — state law would have allowed the town to demand one more space, and Plaistow simply didn't. You only need to show existing/proposed parking on your sketch plan. • YOUR CHOICE OF ENTRANCE for an attached unit — independent door or through shared common space (§220-57.A). • OWNER-OCCUPANCY IS REQUIRED, but you pick which unit you live in — main house or the ADU. Either way, the ADU can be rented, and there is no short-term-rental prohibition written into Article VIII. • You do NOT need separate utility meters, and you do NOT need separate septic systems (though you DO need a state-approved septic design that separately lists the bedroom counts for both units, plus a test pit witnessed by the town Health Officer). • A second-story ADU on top of an existing structure is expressly allowed. Height limit is the ordinary district limit (45 ft / 3 stories in MDR, LDR, RC1).
WHERE PLAISTOW STILL GOES FURTHER THAN STATE LAW LETS IT (the fine print the town's own webpage won't tell you): 1. THE ORDINANCE ASSUMES YOUR HOUSE ALREADY EXISTS. Article VIII is written around adding an ADU to a lot that already has a single-family dwelling. State law (RSA 674:71, I) says an ADU 'may be constructed at the same time as the principal dwelling unit.' If you're building new, you're entitled to permit both together — the state wins this one. 2. SINGLE CURB CUT. §220-57.M requires the house and the ADU to share one driveway entrance onto a Class V or better road. If the town applies that standard to every lot, it's probably lawful parity. Where it gets shaky is a pre-existing detached garage that already has its own drive — state law (RSA 674:72, XI) says the town must let you convert that garage. Flag an existing second curb cut with the town early. (Don't rely on the statute's 'ingress and egress' sentence — that one is about which DOOR an attached unit uses, not driveways.) 3. MOBILE HOMES ARE FLATLY EXCLUDED. §220-57.C says the principal dwelling 'shall not be a Mobile Home.' The state ADU law lists the exclusions a town may make — townhouse-style attached homes, and rented/leased land — and mobile homes are not on that list; NH separately protects manufactured housing that qualifies as a single-family dwelling. If that's you AND YOU OWN THE LAND UNDER YOUR HOME, do not accept a denial without legal advice. If your home sits on a leased park lot, the town can lawfully say no on that basis alone (see below). 4. AN ADU-ONLY SEPTIC GATE. Before you may even file your septic design with the State (NHDES), §220-57.I.2 requires a test pit dug and WITNESSED by the Town Health Officer, plus a town review of the design. State law says a town 'may not impose greater requirements for a septic system for a single-family home with an accessory dwelling unit than is required by the department of environmental services' — and NHDES does not require a town-witnessed pit. Untested, but it's a real cost/schedule gate worth pushing on. 5. LOT SIZE AMBIGUITY. A general ordinance clause (§220-35) says each 'Structure containing Dwelling Units' on a lot must meet the minimum lot size as if it were on its own lot. Read aggressively, that could be used to demand double the lot area for a DETACHED ADU (e.g. 80,000 sq ft in MDR instead of 40,000). The better reading is that §220-35 covers multiple PRINCIPAL uses and an ADU is an ACCESSORY use — and Article VIII itself imposes no lot-size gate at all — but it's worth confirming in writing before you design a detached unit.
WHERE PLAISTOW IS RESTRICTIVE BUT STATE LAW LETS IT BE — DON'T HIRE A LAWYER OVER THESE: • NO ADUs ON LEASED OR RENTED LOTS (§220-57.G). This one looks like overreach and isn't. RSA 674:72, I says in so many words: 'The municipality may prohibit accessory dwelling units associated with rented or leased land.' If your house sits on a ground lease or a manufactured-housing park lot, Plaistow's no is a lawful no and you have no state-law argument against it. • NO CONDO CONVERSION of the ADU (§220-57.H) — expressly authorized by the same paragraph. • ONE ADU PER LOT, OWNER-OCCUPANCY of one of the two units, IMPACT FEES, and NO CAMPERS/RVs AS AN ADU — all permitted by the statute.
BUDGET NOTE: Plaistow charges THREE impact fees on a new ADU (paid to the Planning Department on separate checks after trade inspections), plus a blower-door test and a joint Fire Department / Building Inspector life-safety inspection before your Certificate of Occupancy is issued. Impact fees are permitted under state law — budget for them.
See conflicts[] for the exact statutory citations and resolved_by_town[] for everything Plaistow got right in the 2026 rewrite.
Primary source: Town zoning ordinance (PDF) — Article VIII last amended 3-10-2026 by Art
Get a free personalized report for your address in Plaistow — including where the 2025 law works in your favor.
Get My Free Plaistow ADU Report →House Bill 577 (2025) amended RSA 674:72, effective July 1, 2025. Wherever Plaistow's ordinance is stricter than this floor, the state law controls. Read the full NH ADU law explainer →
Yes — Plaistow allows one accessory dwelling unit, attached OR detached, BY RIGHT in every district that permits single-family homes. Building permit only: no special exception, no conditional use permit, no board hearing. 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 (garage conversions allowed). Since July 1, 2025, state law allows detached ADUs by right statewide — town provisions that prohibited them are superseded.
No requirement — 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.