Amherst Sets Adu Housing Test as Nine Permits Top 900-Square-Foot Limit
Amherst adu housing permits are drawing scrutiny after plans for several recently approved units appeared to exceed the town's 900-square-foot limit for protected accessory dwelling units. Building Commissioner Rob Morra says the second floor in the disputed plans should count as attic space instead.
At least 21 permits for new accessory dwelling units were issued in Amherst over the last five months, and another five to seven applications were pending when the story was written. At least nine of the recently permitted protected-use units appeared larger than 900 square feet based on the plans filed with the town.
Morra’s attic reading
Neighbors of some of the units raised the apparent bylaw issue with Morra, according to the facts provided. He said the original approved designs were adjusted so the second floor now measures 291 square feet, and he described that space as attic under Amherst's zoning rules.
Morra said state regulations do not define attic, but Amherst's Zoning Bylaw Section 6.18 does and excludes attic space from the gross floor area calculation. His explanation was that the second floor constitutes attic space and should not be included in the GFA calculation.
Chestnut, Taylor, Gray, Newell
The disputed plans for ADUs on Chestnut Street, Taylor Street, Gray Street, and Newell Court show two bedrooms with walk-in closets and a bathroom on the second floor. The drawings also show a stairway from the first floor and ceiling heights above 8 feet on the second floor.
The town adopted its two-tiered accessory dwelling unit bylaw in November 2025 to conform with a new state law. Under that system, the state allows protected ADUs up to 900 square feet by right, while Amherst's bylaw also allows local ADUs up to 1,200 square feet if either the ADU or the principal dwelling is owner-occupied.
Amherst Zoning Bylaw Section 6.18
The bylaw definition quoted in the article says a half-story in a top floor shall be a lawful habitable space with required means of access and egress and in which a minimum seven-foot floor-to-ceiling height exists in at least half of the habitable floor area but no less than one-third of the habitable floor area of the full story below. That language now sits at the center of how Amherst will treat the recently permitted units.
For residents watching the issue, the practical question is whether the town treats the filed second-floor space as part of the dwelling's gross floor area or as attic. If Morra's reading holds, some permits now under scrutiny can remain in the protected category even though their plans show finished second-floor rooms.
