New Hampshire ADU Statute Mandates Local Authorization

Enacted in 2017, RSA 674:71 declares that ADUs are an essential component of housing options. RSA 674:72 mandates that municipalities with zoning ordinances permitting single-family detached homes must allow at least one attached or detached ADU as a matter of right or by conditional use or special exception. RSA 674:73 sets baseline standards: ADUs must allow at least 750 square feet, may require interior connection or detached configuration depending on local rules, and cannot be prohibited outright. Municipalities may regulate dimensional standards, owner-occupancy, parking, and aesthetic compatibility but cannot impose family-relationship requirements or short-term rental conversion bans through ADU rules alone.

Local ordinances inconsistent with RSA 674:71-73 are unenforceable; aggrieved property owners may appeal denials to zoning boards and superior court for relief.