ADU rules in New Bedford

New Bedford rewrote Section 2340 of its zoning ordinance in an ordinance that took final passage at the February 12, 2026 City Council meeting, replacing a 2003 section that confined every ADU to 'the existing residential structure on the premises' and so made detached units impossible. The new Section 2340 allows accessory dwelling units by right in any zoning district where single-household residential dwellings are a permitted or allowable use (RA, RAA, RB, RC and MUB in Appendix A, Table 2230) and, notably, on any lot in any district that already holds a single-household, two-household or multi-household use. Detached units must sit behind the primary dwelling in the rear yard, no closer than 18 inches to a side or rear lot line, or in a side yard at least 5 feet behind the front facade and 6 feet from the side lot line, and may be no taller than the height allowed for a single-household residence. Converting an existing non-conforming accessory structure such as a garage or carriage house is allowed if the Inspector of Buildings finds the nonconformity will not be increased; if it would be, the Board of Appeals decides after a public hearing.

The same rewritten Section 2340 covers attached units: an ADU inside the principal dwelling (a basement or attic conversion) or built as an addition is allowed by right on the same terms as a detached one, with no zone-by-zone distinction. Section 2343 adds only two attached-unit standards: the unit must have a separate entrance, either directly to the outside or through an interior entry hall or corridor shared with the principal dwelling, and any stairways or access and egress alterations must be enclosed, screened, or located to minimize visibility from public ways. Statewide law reaches the same result independently: M.G.L. c. 40A § 3, as amended by the Affordable Homes Act effective February 2, 2025, bars a city from prohibiting or requiring a special permit for a single ADU in a single-family residential zoning district.

Section 2342.ii tracks the state protected-use ceiling for by-right units and then uses the local option the statute leaves open, letting the Board of Appeals grant a special permit for an ADU greater than 900 square feet and no more than 1,200 square feet. A detached unit is separately capped in height: the building containing it may be no higher than the allowable height for a single-household residence in that district (§ 2344.ii). The repealed 2003 standards (a flat 1,000 sq ft cap, and a rule that ADU construction could not add more than 15 percent to the gross floor space of the structure as it existed on December 23, 2003) no longer apply. For reference, the state floor in M.G.L. c. 40A § 1A defines a protected ADU as one no larger than half the principal dwelling's gross floor area or 900 square feet, whichever is smaller.

The rewritten Section 2340 through 2345 contains no owner-occupancy condition anywhere. The requirement it replaced was explicit: former § 2343 demanded a certification by affidavit that, while the accessory dwelling unit is occupied, the primary dwelling be occupied by the owner of the property, and the special permit lapsed every two years. State law independently forbids the requirement: M.G.L. c. 40A § 3 provides that use of land or structures for a protected ADU 'shall not require owner occupancy of either the accessory dwelling unit or the principal dwelling', and 760 CMR 71.00 likewise bars a municipality from conditioning an ADU on owner occupancy or on a family relationship between the occupants.

Section 2342.iv requires one additional off-street parking space for an ADU, constructed of materials consistent with the existing driveway and with vehicular access to it, and lets the Board of Appeals grant a special permit waiving that space where there is no suitable location on the lot or a waiver is otherwise in the public interest. The exception swallows much of the rule in a city like New Bedford: no additional parking may be required at all for an ADU on a lot within a half mile of a transit station as defined in 760 CMR 71.02, and that regulation defines Transit Station as a Subway Station, Commuter Rail Station, Ferry Terminal or Bus Station, with Bus Station meaning 'a location serving as a point of embarkation for any bus operated by a Transit Authority'. Any SRTA bus stop therefore counts, as does the New Bedford commuter rail station, so a large share of city lots owe no ADU parking. Measure the actual half-mile distance for a specific parcel rather than assuming.

A conforming ADU needs only a building permit: § 2341 authorizes the Inspector of Buildings to issue a building permit creating an accessory dwelling unit, and even lets the Inspector waive requirements of the section that would amount to an 'unreasonable regulation' under 760 CMR 71.03(3). The application needs a scaled floor plan (no licensed design professional required unless the State Building Code demands one) and, for a detached unit or an addition, a plot plan by a registered land surveyor showing existing and proposed structures, septic, utilities and parking; a properly adapted mortgage inspection survey suffices. Discretionary review appears only at the edges: a Board of Appeals special permit for a unit over 900 square feet, to waive the parking space, or where converting a non-conforming accessory structure would increase its nonconformity. This replaces the 2003 regime, under which every ADU needed a Board of Appeals special permit that lapsed and had to be renewed every two years.

Section 2345 is blunt: no accessory dwelling unit may be used as a short-term rental as defined in § 1200, and an ADU, if rented, must have a tenancy term of more than thirty-one days. The § 1200 definition of short-term rental covers any furnished accommodation other than a hotel, motel, lodging house or bed and breakfast that is reserved in advance and rented for not more than thirty-one days, so the ban reaches Airbnb-style use of the unit. The city took this option deliberately; state law allows it, since M.G.L. c. 40A § 1A permits municipalities to impose 'restrictions or prohibitions on short-term rental, as defined in section 1 of chapter 64G' while forbidding unreasonable restrictions on creating or renting an ADU that is not a short-term rental. Nothing in the zoning ordinance limits ordinary year-round tenancies, caps rent, or requires the tenant to be related to the owner, and the ADU cannot be sold separately because it must share a lot with the principal dwelling.