Advisory committee declines endorsement of ADU bylaw change after split vote

Doris Cahill, a representative of the Zoning Board of Appeals, outlined a draft warrant article that would change Southborough’s accessory dwelling unit (ADU) rules to allow ADUs up to 1,200 square feet by right, remove the town’s special‑permit requirement for ADUs, and lift a separate size cap for adaptive reuse of historic buildings.

Cahill told the advisory committee that the proposal grew from months of work between planning and the ZBA and was intended to address what she described as an ‘‘unfairness’’ for smaller homes under the existing 50 percent (half‑gross floor area) rule. ‘‘We ultimately ended up with 1,200 square feet as an upper limit,’’ Cahill said, adding that other zoning controls — setbacks, height limits and health and sewer requirements — would still apply.

Committee members pressed for detail on potential side effects. One member said a 1,200‑square‑foot ADU ‘‘could be basically putting two homes on a lot’’ in some sections of town and asked how the change would interact with two‑family zoning and lot‑size rules. Cahill responded that the change would not eliminate setbacks or other zoning limits and that the town’s building and permitting process would remain the enforcement mechanism. She noted the town inventory showed only about 34 ADUs in town, most associated with larger properties.

Members also raised questions about parking and school impacts. The committee asked who would verify parking and compliance if ADUs were authorized by right; Cahill and others said the building commissioner enforces those requirements during permit and construction review. Several members said they sympathized with the aim of expanding housing options but remained unconvinced that the proposed 1,200‑square‑foot cap struck the right balance for Southborough’s character and services.

After discussion, a motion to support Article 29 was made and seconded. In a roll‑call vote the advisory committee recorded 2 votes in favor and 5 votes not in favor; the committee did not recommend support for the warrant article. The committee chair said the article, and the final disposition, will go before town meeting for a final decision.

What happens next: The article will appear on the town meeting warrant; advisory’s vote and the committee’s reservations about size, by‑right effects and enforcement will be recorded in its advisory letter to voters.