Southborough planning board sets ADU cap at 1,200 sq. ft., schedules March public hearing

The Southborough Planning Board on Feb. 23 reviewed a revised accessory dwelling unit (ADU) bylaw that would allow ADUs up to 1,200 square feet gross floor area, not to exceed the size of the primary dwelling, and open a public hearing on March 9.

Planner Corina told the board that Laura Davis updated the draft to reflect a 1,200-square-foot threshold and that the revised text and a comparative spreadsheet were posted to the meeting Dropbox and emailed to members. "Up to 1,200 square feet gross floor area, not to exceed the primary dwelling unit," Corina said when summarizing the change.

Doris from the Zoning Board of Appeals said she had reviewed the revisions and the accompanying spreadsheet. She told members the list was pulled with assessor data and identified 34 ADUs permitted through the ZBA; Corina added that three recent ADUs were permitted administratively through the building department under state regulations. "The spreadsheet is very up to date," Doris said.

Board members broadly favored removing the ADU from special-permit review where possible to simplify administration, but several urged a careful cross-code review. Planning board member Marnie Houlihan cautioned that references to ADUs appear in other parts of the town code and recommended an additional pass to capture any scattered references before the warrant article is finalized.

Corina reviewed the warrant calendar for the April town meeting: the warrant opened Dec. 16, closes March 10, and the select board will sign by March 17 with the warrant to the printer on March 18. She also reported that the Attorney General had approved most of the ADU article submitted for Town Meeting 2026, but removed a prohibition on mobile homes or trailers from the text.

Next steps: the board will finalize whether the by-right allowance will be limited to one ADU per lot (several members favored explicitly stating "one ADU per lot"), confirm cross-code updates, and hold the public hearing on March 9. The Town Clerk and town counsel will continue to be consulted on final warrant language and formatting.