New Hampshire residential & ADU permit data
One ADU by right with every single-family home
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Housing law
New Hampshire's 2016 ADU law (effective 2017) requires municipalities to allow at least one accessory dwelling unit with a single-family home as of right; a 2025 expansion (HB 577) extended this to allow a detached ADU.
New Hampshire has no comprehensive statewide duplex mandate; recent reform (HB 631, effective 2026) instead requires municipalities to allow multifamily housing on commercially zoned land where infrastructure allows.
Major permit jurisdictions
Why Igni for New Hampshire
An early-mover statewide ADU market with steady single-family growth
Track by-right ADU permits attached to single-family homes
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Permit data via municipal open-data portals and public records where available.
Informational only, not legal advice. Housing law changes — verify current statutes before relying on this.