Planning Board reviews ADU bylaw revisions; members favor clarity on design and building-code compliance

Planning staff presented proposed edits to the Town of Sudbury’s accessory dwelling unit (ADU) bylaw at the March 12 Planning Board meeting, including suggested changes from town counsel and outside review. Board members discussed language addressing the definition of gross floor area, design standards for attached and detached ADUs, building-code compliance, parking materials, and new curb cuts.

Adam (staff) said counsel had suggested importing the statutory definition of gross floor area (referred to in the draft as a change to section 55‑25) and other minor drafting changes. Board members generally favored retaining explicit language in the bylaw to make requirements clear to builders and homeowners. Several members urged keeping a provision that makes clear ADUs must meet building-code requirements for egress, fire separation and alarms.

A substantive discussion focused on whether the bylaw should require a detached ADU to “appear” accessory to the primary dwelling versus allowing a detached building to read as a second house. Members suggested splitting the draft into a structure such that: (1) all ADUs must meet basic building-code requirements; (2) attached ADUs must maintain the appearance of a single-family dwelling and not read as a duplex; and (3) detached ADUs should appear as accessory structures and be architecturally harmonious with the primary dwelling. Board members discussed adding explanatory language to multiple subparagraphs to emphasize retaining the single-family character and to help reviewers and builders understand design intent.

The board also considered parking and driveway language. Members raised concerns about prohibiting parking within a front setback given existing neighborhood patterns (e.g., Pine Lakes) where driveways already fall partially within the setback. The board favored removing a blanket prohibition that would create a new zoning restriction on parking. Instead, they discussed requiring that parking spaces be constructed of materials suitable for vehicular use (allowing pervious pavers or gravel, for example) rather than allowing improvised grass parking that can become muddy.

On new curb cuts, board members said installing a curb cut or additional driveway connection is governed by DPW approval and should not be treated as a by-right element of creating an ADU. The board favored keeping a line that requires a separate approval for new curb cuts rather than automatically allowing them as part of an ADU application, and suggested making that item a separate subparagraph to reflect that it is a distinct process from the ADU standard.

Several members asked staff to make targeted wording edits: keep a clear statement that all ADUs must meet building-code requirements; split the design requirements into distinct statements for attached and detached units; adjust the parking language to require “vehicular hardscape” or “materials suitable for vehicular use” rather than specifying exact materials; and retain a process requirement that new curb cuts require DPW approval. Staff said they would incorporate the changes and forward the revised draft to town counsel for inclusion on the warrant.