The accessory dwelling unit planned for 27 Newell Court has a ground floor of 891 square feet. Upstairs, in the plans the Zoning Board of Appeals discussed, a 297-square-foot level holds two bedrooms, a bathroom and closets, which makes it a four-bedroom unit on two floors. Whether that upper floor counts toward the unit's size has gone from the building commissioner to the ZBA to Land Court. In Amherst, a unit's floor area helps decide whether it can be rented out freely or whether an owner has to live on the property.
For a buyer looking at a home with a backyard unit, or a lot where they might add one, that classification affects whether an owner has to live there, how the town taxes the unit, and whether its permit could be challenged.
Where the bylaw draws the line
Amherst amended its accessory dwelling unit bylaw on November 17, 2025, and the change took effect December 1, 2025. It sets up two kinds of ADU in the town's single-family districts. The full bylaw text lays out both tracks:
| Protected Use ADU | Local ADU | |
|---|---|---|
| Size limit | 900 sq ft or half the main house's gross floor area, whichever is smaller | Larger than a Protected Use ADU, up to 1,200 sq ft |
| Permitting | As of right, through a building permit | Administrative Approval, or a ZBA special permit if the lot already has a Protected Use ADU |
| Owner occupancy | Cannot be required under state rules | The owner must live in the main house or the ADU, recorded as a deed restriction at the Registry of Deeds |
| Design rules | The most permissive dimensional rules apply | Must match the main house in appearance and scale |
The owner-occupancy rule comes from state law. Under the Affordable Homes Act, whose ADU provisions took effect February 2, 2025, cities and towns cannot require an owner to live in a protected ADU or in the main house. They can require at most one parking space for a protected unit, and none within half a mile of a commuter rail station, subway station, ferry terminal or bus station. The state's Accessory Dwelling Units page lays out those limits.
So the gap between the two caps also decides whether an owner has to live on site. A unit within the protected limit, which is 900 square feet or half the main house, whichever is smaller, carries no owner-occupancy requirement, so the unit and the house can both be rented. A Local ADU comes with a deed restriction requiring the owner to live in one of the two units, so the property works for a buyer who plans to live there and not as a pure rental. Either way, any rented unit has to be registered and permitted under the town's Residential Rental Property Bylaw.
How a second floor came to be called an attic
The bylaw counts floor space of code-compliant ceiling height toward gross floor area. It excludes "crawl spaces, garage parking areas, attics, enclosed porches, and similar spaces." It does not define "attic." Building Commissioner Rob Morra decided that an upper floor too small to count as a half-story, meaning less than one-third of the habitable area below, is an attic by default. That left it out of the 900-square-foot total.
The Amherst Indy reported in May that plans on Chestnut, Taylor and Gray streets and Newell Court showed second floors with two bedrooms, walk-in closets, a bathroom, a stairway and ceilings above 8 feet. In the same report, Community Resources Committee Chair Pam Rooney told the Indy that councilors were never told this was possible during adoption. She wrote:
"Therefore, an ADU could contain 900 square feet on the main floor plus up to 300 square feet of attic space. Is that what you, council members, want?"
If the upstairs counts as an attic, a design with a first floor under the protected limit gets a four-bedroom unit with as-of-right permitting and no owner-occupancy deed restriction. By October 2026, Amherst had issued at least 40 ADU permits under the new bylaw, and at least 12 were for two-story units whose finished second floor had been classified as an attic.
A permit that was overturned, and a lawsuit over nine more
That classification has not held up everywhere. On August 13, 2026, after an abutter's appeal, the Zoning Board of Appeals reversed the commissioner's approval of the 27 Newell Court unit. According to the Amherst Indy's account of the filing, the property owners filed in Land Court on August 25. They argued that the commissioner read the bylaw correctly and that the appeal was filed too late. Counting the upper level, the design totals 1,188 square feet, inside the Local ADU cap but over the protected limit.
The complaint lists nine more properties owned by the plaintiffs that use the same design and are planned or under construction. When the suit was filed, only the Newell Court and Taylor Street buildings were nearing completion. The rest had foundations poured or were waiting for permits. The streets named are:
- Gray Street
- Pine Street
- North Whitney Street
- South East Street
- Chestnut Street
- Shays Street
- West Street
- Taylor Street
- College Street
The same layout reached Lincoln Avenue. Matching ADUs proposed at 290 and 321 Lincoln Avenue each put 900 square feet above a three-car garage, plus another 300 square feet for two bedrooms and a bathroom. At a September 8 follow-up, the 290 Lincoln redesign had dropped the top floor and the garage, moved the unit behind the house, and come in at the 900-square-foot maximum. Under review, the design moved back to the protected limit.
The rewrite up for a hearing on November 12
A Planning Department memo dated September 23, 2026 proposes counting all code-compliant floor area in any ADU toward gross floor area. It would define an attic as space above a story or half-story, or behind eave walls, that lacks the ceiling height and room dimensions the Building Code requires for habitable use. The memo says the half-story and attic changes would apply to all residential buildings, not just ADUs.
The Planning Board and the Community Resources Committee opened a joint hearing on October 22. The Amherst Indy reported that members generally agreed enclosed porches with compliant ceiling height should also count, even though state law currently excludes them. The hearing continues November 12 at 6:30 p.m. Planning and Economic Development Director Jeff Bagg said any protected-use ADU application filed after the hearing was noticed on October 6 must meet the proposed amendments until they are adopted or rejected. The Town Council set a December 2 deadline for the boards' hearings.
The state is revising its rules at the same time. The Executive Office of Housing and Livable Communities took public comment on draft amendments to its ADU regulations from September 11 to October 9, and Mass.gov still lists them as proposed. That draft would exclude common areas, enclosed exterior stairs, breezeways and egress areas from a protected unit's floor area. As a result, the floor-area rules for a unit bought this fall depend on when its application was filed, and they could change again before the state finalizes its rules.
The extra square footage shows up in tax bills and prices
How a unit is classified also affects what it costs to own. Amherst's October 19 FY2027 tax classification presentation estimated a single rate of $17.10 per $1,000 of value. On an average single-family value of $611,574, that works out to an estimated annual bill of $10,457.92. The rate is an estimate until the state posts it. In May, the Amherst Indy put the yearly tax difference between a two-bedroom, 900-square-foot unit and a four-bedroom, 1,200-square-foot unit at roughly $3,000. A unit taxed on one count and appraised on the other has to be reconciled somewhere.
These units are being built while values climb. In September 2026, Hampshire County's single-family median sale price was $494,950, up 10.0% from $450,000 a year earlier, on 92 closed sales, according to the Realtor Association of Pioneer Valley. That is a county figure, not an Amherst one. With prices rising, a backyard unit's legal status can account for a meaningful share of what a buyer pays for the property.
FAQ
Does a home with a protected ADU come with an owner-occupancy requirement? No. State rules prohibit requiring owner occupancy of a protected ADU or the main house. A Local ADU of up to 1,200 square feet requires the owner to live in one of the two units, and that requirement is recorded as a deed restriction.
Can a lot have more than one ADU? Amherst's bylaw allows one Local ADU and one Protected Use ADU on the same lot. If a protected unit is already there, adding the Local ADU requires a ZBA special permit.
Can an ADU be sold separately as a condominium? EOHLC says condominium conversions fall under M.G.L. c. 183A, not the ADU law, and refers owners to legal or real estate advice.
Is 900 square feet always the protected limit? No. Under the bylaw, the cap is 900 square feet or half the main house's gross floor area, whichever is smaller, so a unit attached to a smaller house reaches the limit sooner.
This post is general information, not legal, tax or financial advice. Please confirm how any rule applies to a specific property with an attorney, the town's Building Department, or a tax professional.
If you're weighing an Amherst property with a backyard unit, or a lot where you might build one, Cheryl Zarella and our team can help you gather the permit records and set them beside recent comparable sales before you write an offer. If you already own an Amherst home with an ADU, request a complimentary home valuation, and we'll account for how the unit is classified.
