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ADU Rules in Belknap County, New Hampshire

4 towns covered · 2 human-verified · Reconciled with the 2025 state law · Last reviewed 2026-09-10
The short answer
Every town in Belknap County must allow one ADU — attached or detached — by right on single-family lots.

That's the statewide floor under RSA 674:72, effective July 1, 2025. What differs town to town is the details: size caps, parking, owner-occupancy, and how much of each town's posted ordinance the state law now overrides. Pick your town below for the plain-English breakdown.

Belknap County towns

Alton

Alton's ADU ordinance (Zoning §319) hasn't been amended since March 2018 — years before New Hampshire's July 2025 ADU law took effect — so several of…

Read the full Alton ADU guide →
Center Harbor

State law now guarantees Center Harbor homeowners a detached-ADU option, entrance choice, and nonconforming-lot protection — the town's ADU rules…

Read the full Center Harbor ADU guide →
Laconia ✓ Human-verified

Yes — Laconia allows one ADU (verified with the town), up to 1,000 sq ft.

Read the full Laconia ADU guide →
Meredith ✓ Human-verified

State law now guarantees one ADU by right; Meredith calls it an 'Accessory Apartment' and hasn't touched its rule since 2008, so several of its…

Read the full Meredith ADU guide →

Coming soon: Gilmanton.

Not sure what your lot allows?

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Learn the statewide law

Wherever a town's rules are stricter than the state floor, the state law controls. Read the full New Hampshire ADU law explainer →

Other counties

Rockingham CountyHillsborough CountyStrafford CountyMerrimack CountyCarroll CountyGrafton County
This guide is an independent informational resource, not legal advice; confirm details with your town's planning department before you build.