Hudson, NH Accessory Structures: ADU Rules (2026)

3, allows an accessory dwelling unit only inside a single-family dwelling in a district that permits single-family homes; it is not allowed in a two-family or multifamily building or in any nonresidential use. Subsection B is unambiguous that an ADU cannot be a freestanding detached structure or part of any structure detached from the principal dwelling, and it specifically bars manufactured housing, recreational vehicles or trailers from being added to the principal dwelling as an ADU. Either the principal dwelling unit or the ADU has to be occupied by the property's owner of record under subsection C, and the owner must prove that residency to the Zoning Administrator on request.

The front of the house has to keep looking like a single-family home after the conversion, with any new separate entrance placed on the side or rear under subsection D, and subsection E requires at least one shared interior access between the two units along with two separate means of egress. Size is tightly bounded: subsection H sets the ADU itself at no less than 350 and no more than 750 square feet, and the principal dwelling cannot shrink below 850 square feet to make room for it.

Subsection I caps an ADU at two bedrooms, subsection M caps occupancy at two unrelated people, and subsection G requires four off-street paved parking spaces total for both units combined, with no separate driveway for the ADU. A building permit has to be approved before any construction or conversion begins under subsection J, and subsection O requires the owner to file proof that water supply and sewage disposal comply with RSA 485-A:38 before the Town issues that permit.