Planning board hears ZBA-backed changes to ADU bylaw, continues hearing to March 23

The Southborough Planning Board heard a proposed zoning amendment on Monday to update rules for accessory dwelling units, commonly called ADUs, that would align the town—ode with state by-right ADU requirements and make the rules easier for owners of smaller homes.

The draft before the board would allow a single ADU per lot and permit ADUs up to 1,200 square feet as-of-right, provided the ADU does not exceed the gross floor area of the principal dwelling. The proposal also removes a special-permit path that previously applied in some districts and renumbers and corrects cross-references throughout the zoning code.

David Williams, chair of the Zoning Board of Appeals, told the planning board the ZBA prepared the warrant language and has worked with town counsel to land on the current draft. "Only one accessory dwelling unit may be established on a lot," Williams said, summarizing the core change the ZBA is asking town meeting to adopt.

Doris Cahill, ZBA member, said the change is intended to simplify the process for smaller homeowners who could not practically use the prior percentage-based rules. "It was to simplify what small home needs," Cahill said, noting the ZBA examined other towns' approaches and recommended a straight square-foot cap rather than complicated percentage formulas.

Several residents asked for clarification about where the special-permit option had been removed and how the revisions would apply in nonresidential and industrial districts. John Badalini, a resident of Wyeth Circle, urged the board not to eliminate all forms of discretionary review that could be used in atypical cases, such as conversions that previously relied on special-permit thresholds.

Planning staff confirmed the version to be sent to the warrant is the draft dated 2026-02-25, which includes the "only one ADU per lot" sentence and the 1,200-square-foot by-right cap. The board voted to continue the public hearing to March 23, 2026, to allow time for final edits and distribution of the revised language to town officials and the public.

The board did not take final action on the amendment; the next hearing will again invite public comment before the board forwards a recommendation to the town meeting warrant.

What happens next: The planning board is scheduled to continue the ADU bylaw public hearing at its March 23 meeting. If the board votes to place the article on the warrant, voters at town meeting will consider the change.