Board moves ADU bylaw draft forward; members back 1,200-square-foot cap and no-ADU-larger-than-primary rule

The Southborough Zoning Board discussed the draft accessory dwelling unit (ADU) bylaw at its Feb. 11 meeting and signaled support for simplifying size rules and moving a proposal toward the April 11 annual town meeting warrant.

Board members said the existing 50% rule was confusing and suggested numeric caps. "Why don't you just say 1,200?" one board member asked. Doris and other members reported positive feedback from the Planning Board and indicated the suggested approach — removing the special-permit requirement and capping ADUs at 1,200 square feet while also requiring an ADU not exceed the primary residence’s size — was well received.

Members noted the draft may require bylaw relettering and legal review, and planning staff said final language will be needed to meet legal-ad posting deadlines for a public hearing. Laura said she will compile comments and coordinate with the planning department and town counsel on final edits. The board agreed to forward materials and asked members to send comments to staff ahead of the next steps.

If finalized, the revised language would permit a limited-size ADU by right (subject to the code’s definitions) and avoid the larger special-permit pathway for qualifying ADUs, while keeping restrictions to prevent the ADU from becoming larger than the main home.