New Hampshire Accessory Dwelling Unit Regulations
Outside the west coast, few states mandate municipalities allow homeowners to construct accessory dwelling units. The jurisdictions that do allow ADU’s often put unnecessary burdens on homeowners such as lot size limitations, setback requirements, etc. The most restrictive rule is a family member has to live there.
Fortunately, NH passed RSA 674:71 (see below) that forces towns to create a reasonable ADU zoning ordinance. While each municipality creates their own regulations, the state law guides them. For example, the owner can live in the ADU and rent the main house to anyone and receive a sizeable monthly income.
Section 674:71 Definition
As used in this subdivision, “accessory dwelling unit’’ means a residential living unit that is within or attached to a single-family dwelling, and that provides independent living facilities for one or more persons, including provisions for sleeping, eating, cooking, and sanitation on the same parcel of land as the principal dwelling unit it accompanies.
Section 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 as a matter of right or by either conditional use permit pursuant to RSA 674:21 or by special exception, in all zoning districts that permit single-family dwellings. One accessory dwelling unit shall be allowed without additional requirements for lot size, frontage, space limitations, or other controls beyond what would be required for a single-family dwelling without an accessory dwelling unit. 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, and with manufactured housing as defined in RSA 674:31. 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 a building permit, if necessary.
III. An interior door shall be provided between the principal dwelling unit and the accessory dwelling unit, but a municipality shall not require that it remain unlocked.
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. A municipality may require adequate parking to accommodate an accessory dwelling unit.
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 establish standards for accessory dwelling units for the purpose of maintaining the aesthetic continuity with the principal dwelling unit as a single-family dwelling. A municipality may also establish minimum and maximum sizes for an accessory dwelling unit, provided that size may not be restricted to less than 750 square feet.
VIII. A municipality may not require a familial relationship between the occupants of an accessory dwelling unit and the occupants of a principal dwelling unit.
IX. A municipality may not limit an accessory dwelling unit to only one bedroom.
X. An accessory dwelling unit may be deemed a unit of workforce housing for purposes of satisfying the municipality’s obligation under RSA 674:59 if the unit meets the criteria in RSA 674:58, IV for rental units. Section 674:73 Detached Accessory Dwelling Units A municipality is not required to but may permit detached accessory dwelling units. Detached accessory dwelling units shall comply with the requirements of, and any municipal ordinances or regulations adopted pursuant to, RSA 674:72, IV through IX. If a municipality allows detached accessory dwelling units, it may require an increased lot size.
Statute text includes amendments adopted by the Legislature in 2017
