RSA 674:72. Accessory Dwelling Units.

I. A municipality that adopts a zoning ordinance pursuant to the authority granted in this chapter shall allow accessory dwelling units in all zoning districts that permit single-family dwellings. One accessory dwelling unit, which may be either attached or detached, shall be allowed as a matter of right. The municipality shall allow one accessory dwelling unit without additional requirements for lot size, except as described by this section, setbacks, aesthetic requirements, design review requirements, frontage, space limitations, or other controls beyond what would be required for a single-family dwelling without an accessory dwelling unit. The municipality 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. The municipality is not required to allow more than one accessory dwelling unit for any single-family dwelling. The municipality may prohibit accessory dwelling units associated with multiple single-family dwellings attached to each other, such as townhouses. The municipality may prohibit accessory dwelling units associated with rented or leased land. Subsequent condominium conveyance of any accessory dwelling unit separate from that of the principal dwelling unit shall be prohibited, notwithstanding the provisions of RSA 356-B:5, unless allowed by the municipality. II. If a zoning ordinance contains no provisions pertaining to accessory dwelling units, then one accessory dwelling unit shall be deemed a permitted accessory use, as a matter of right, to any single-family dwelling in the municipality, and no municipal permits or conditions shall be required other than building permits, if required by statute. III. Attached accessory dwelling units shall have either an independent means of ingress and egress or ingress and egress through a common space shared with the principal dwelling. However, the municipality shall not limit the choice of ingress and egress. IV. Any municipal regulation applicable to single-family dwellings shall also apply to the combination of a principal dwelling unit and an accessory dwelling unit, including but not limited to lot coverage standards and standards for maximum occupancy per bedroom consistent with policy adopted by the United States Department of Housing and Urban Development, provided that such municipal regulations shall not be more restrictive for accessory dwelling units than for any single-family use in the same zoning district. If a municipality has established regulations requiring parking for the principal dwelling unit, it may require up to one additional parking space for each accessory dwelling unit. Required parking spaces may be provided either on-site or at a legally dedicated off-site location, at the property owner's discretion. V. The applicant for a permit to construct an accessory dwelling unit shall make adequate provisions for water supply and sewage disposal for the accessory dwelling unit in accordance with RSA 485-A:38, but separate systems shall not be required for the principal and accessory dwelling units. In order to comply with this paragraph and prior to constructing an accessory dwelling unit, an application for approval for a sewage disposal system shall be submitted in accordance with RSA 485-A as applicable. The approved sewage disposal system shall be installed if the existing system has not received construction approval and approval to operate under current rules or predecessor rules, or the system fails or otherwise needs to be repaired or replaced. VI. A municipality may require owner occupancy of one of the dwelling units, but it shall not specify which unit the owner must occupy. A municipality may require that the owner demonstrate that one of the units is his or her principal place of residence, and the municipality may establish reasonable regulations to enforce such a requirement. VII. A municipality may apply aesthetic standards to accessory dwelling units only if it has also applied such standards to the principal dwelling unit. The total living space of the accessory dwelling unit shall not exceed 950 square feet unless otherwise authorized by the municipality. A municipality may not restrict the total living space to less than 750 square feet. VIII. A municipality shall not require a familial relationship between the occupants of an accessory dwelling unit and the occupants of a principal dwelling unit. IX. A municipality shall not limit an accessory dwelling unit to only one bedroom. X. An accessory dwelling unit may be deemed a unit of workforce housing for the purpose of satisfying the municipality's regional fair share obligation under RSA 674:59, III if the unit meets the criteria in RSA 674:58, IV for rental units. XI. A municipality shall allow accessory dwelling units to be converted from existing structures, including but not limited to detached garages, regardless of whether such structures violate current dimensional requirements for setbacks or lot coverage. XII. A municipality shall not deny the establishment of a separate electrical panel and separate electrical service to the accessory dwelling unit. Source: Source. 2016, 6:2, eff. June 1, 2017. 2017, 89:1, eff. June 5, 2017; 238:4, eff. Sept. 16, 2017. 2025, 197:2, eff. July 1, 2025.