New Hampshire’s Accessory Dwelling Unit (ADU) Law - adopted last year as Senate Bill 146 - is set to take effect June 1. Municipalities across New Hampshire have been working to bring local ordinances into compliance.
The new ADU law, codified at RSA 674:71 through 674:73, defines an ADU as “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.”
Upon its effective date, the new law prohibits municipalities from: 1) requiring occupants of an ADU to be related to the occupants of the principal dwelling unit; 2) limiting an ADU to only one bedroom; 3) requiring separate water and sewage systems for the principal dwelling and ADU; and 4) restricting the size of an ADU to less than 750 square feet. The delayed effective date of the new law was designed to give municipalities time to amend their zoning ordinances.
Some municipalities that expressly allow ADUs without limitation may not have had much work to do, because their ordinances were already in compliance.
For other municipalities, such as Effingham, the new law means significant changes to its zoning ordinance. Effingham’s prior zoning ordinance prohibited property owners from having more than one dwelling unit on a lot. Thus, under the old ordinance, a homeowner was not allowed to convert a basement, attic or garage into a separate dwelling unit.
Under Effingham’s amended ordinance, a homeowner may now have one attached or detached ADU, but not both. Either type of ADU requires a building permit and compliance with other requirements in the ordinance.
Other municipalities that already allowed ADUs subject to conditions have had to amend their ordinances to comply with the new law. For example, Manchester amended its ordinance to eliminate the family relation requirement, which is no longer allowed under the new law. Manchester also had to increase the minimum size of an ADU from 650 to 750 square feet and increase the maximum number of bedrooms an ADU could have from one to two.
For municipalities with ordinances that are silent on ADUs, one ADU will automatically be deemed permitted as a matter of right for any single-family dwelling, and only a building permit may be required. To comply with the new law, the Portsmouth City Council passed an ordinance in January which, in addition to attached and detached ADUs, provides for garden cottages as an alternative to detached ADUs. Portsmouth’s ordinance provides that “one garden cottage, and only one, shall be allowed on any lot containing a single-family dwelling.” The ordinance imposes further requirements with which garden cottages must comply.
One of the stated goals for passing the new law was to increase affordable housing opportunities for New Hampshire citizens. When signing the bill into law, then-governor Maggie Hassan commented that “[b]y requiring municipalities to allow one attached accessory dwelling unit to single-family homes in zones that allow those homes and establishing other important requirements for local regulation of these units, this bipartisan bill will help increase affordable housing options, helping to meet workforce demands and allowing more of our older citizens to live independently in their communities.”
Under the old law, municipalities had greater autonomy with respect to how they treated ADUs. The new law limits their ability to regulate ADUs, which will lead to more zoning uniformity throughout the state and likely create some new and unique housing options in New Hampshire.