Tiny home on wheelsNo statewide tiny-home-on-wheels law. This corrects a dating error in an earlier draft: New Hampshire's ADU law is not from 'the early 2020s' — it originates from the 2016 legislative session (Chapter 6 of the 2016 laws), codified at RSA 674:71–73, effective June 1, 2017, making New Hampshire one of the earliest states in the country with a statewide ADU mandate (alongside California, Washington, and Vermont).
ADU / accessory unitThe original 2016 law required municipalities to allow at least one attached ADU by right, conditional use, or special exception in every zoning district that permits single-family homes; if a town's ordinance is silent on ADUs, one is automatically deemed permitted. A 2025 revision (effective July 1, 2025) went further, requiring detached ADUs to be allowed by right as well, not just via conditional use or special exception as under the original law.
Minimum square footageNo statewide minimum; municipalities may not impose lot size, frontage, or setback requirements beyond what applies to a single-family home without an ADU
Foundation requirementFoundation-built ADUs have one of the strongest, longest-standing statewide legal guarantees of any state in this dataset outside the original ADU-preemption states