Sudbury planning director outlines draft ADU bylaw changes under Affordable Homes Act

The Planning Director for the Town of Sudbury, Adam Birney, told the Zoning Board of Appeals that the Planning Board will place a revised Accessory Dwelling Unit (ADU) bylaw on the May town-meeting warrant that implements provisions of the state Affordable Homes Act and the Executive Office of Housing and Livable Communities' implementing guidance.

Birney said the draft would permit a single ADU per property by right through a building permit, capped at 900 square feet or 50% of the primary dwelling, whichever is smaller, and included design and occupancy conditions intended to preserve single-family character while complying with state requirements.

“At the end of last year of some proposed alterations...the bylaw now allows for building permit issuance by right for a singular ADU per property up to 900 square feet or 50% of the primary dwelling, whichever is smaller,” Birney said. He explained the Planning Board narrowed requirements because state guidance makes a site-plan process available only where a town otherwise requires site plan approval for single-family homes.

Birney outlined four practical limitations in the draft: a prohibition on short-term rentals (shorter than the state’s 29‑day threshold for such definitions), a requirement that the primary dwelling and ADU remain under common ownership, a rule barring new driveway connections created specifically to serve an ADU, and preserving the status of preexisting special-permit ADUs. The draft also contains an aesthetic requirement for detached ADUs to be “architecturally harmonious” with the primary structure; Birney said the Planning Board left that clause in the warrant to let the state Attorney General decide its enforceability.

Board members discussed whether larger ADUs (for example, 1,200 square feet) or a different local approval path should be allowed. Birney said those changes could be considered later and that the initial approach is deliberately cautious to implement the new state law quickly while monitoring local impacts. He described the likely pathway for ADUs larger than 900 square feet: applicants would pursue dimensional relief (variance) under existing local rules rather than a new special-permit track in the draft bylaw.

Birney said the Planning Board will distribute the final draft and that staff will circulate the warrant language to the ZBA. He recommended starting with the 900-square-foot threshold to comply with the state law and watch how the bylaw is used before proposing broader allowances.

The board did not take a vote on the draft ADU bylaw during the ZBA meeting; Birney said the Planning Board will forward the warrant article to town meeting for a vote.