Brentwood planning board refines ADU ordinance to match state law, debates size, parking and enforcement

The Brentwood Planning Board continued work on updates to the town’s accessory dwelling unit (ADU) ordinance on Sept. 24, focusing on language needed to conform to recent state legislation while preserving local design and enforcement controls.

Board members and staff said they intend to present a near-final draft for public hearings in November or December and discussed three priority topics for the March public package: ADUs, multifamily zoning and workforce housing. Planning consultant Mark (no last name provided) and board members reviewed tracked edits and agreed to circulate a cleaned-up tracked-changes version with a draft watermark before the next meeting.

The board debated the definition of “detached” ADU, which in the language provided mirrors state text that can read awkwardly; one participant said, “That is odd,” and another noted “it is actually state language.” Members asked staff to check whether the town could expand beyond the state definition where permissible. The group also questioned whether a preexisting barn or garage converted to an ADU would trigger additional structural requirements; staff said the legislative intent was to allow conversions of existing detached structures.

Members spent substantial time on unit size. The draft reflects the recent state-imposed 950-square-foot reference; several members urged higher local maxima, noting many towns set their caps at 1,100–1,200 square feet. Board member Paul (no last name provided) suggested a compromise—“50% or 1,300, whichever is less”—to keep units accessory on smaller homes while allowing two-bedroom ADUs where appropriate. Others noted the town could instead specify a straight square-foot cap rather than a percentage to avoid “gaming” the rule by increasing the primary dwelling’s size.

Parking and curb cuts drew repeated questions. The draft requires “one additional space” for each ADU but board members clarified that the state bars municipalities from requiring more than one mandatory space for an ADU. The board debated whether to limit each property to a single driveway for aesthetic reasons and to preserve a single-family appearance, with exceptions (for example for lots with more than 500 feet of road frontage) handled through the town’s driveway standards or by variance. One member said a variance route was the practical way to handle large or irregular lots.

Members raised enforcement concerns about non‑conditioned spaces and “three‑season porches” being converted later to conditioned living area without a permit. Staff reported a building inspector’s practice in another town (Stratham) requiring wall construction standards when an ADU is created; that approach increases renovation costs later and can deter post‑permit conversions. The group asked staff to research language the town could adopt to reduce the risk of unpermitted conversions (for example, clarifying that living-area counts only heated, finished space) and to consider limiting the role of unconditioned space in ADU size calculations.

On design objectives, members debated whether the ordinance should include an aspirational phrase about retaining neighborhood character “as much as feasible.” Several members recommended striking “as much as feasible” and instead using language tied explicitly to compliance with state law; the board agreed to remove the qualifier and read the purpose statement so it ends with: “retain the neighborhood character and single-family appearance of properties in Brentwood.”

Board members asked staff to add a clear lighting and dark‑skies note and to prepare a public-facing cover sheet and newsletter article summarizing key parameters (density, size caps, parking and driveway rules) for the upcoming hearings.

The board directed staff to clean up tracked changes, provide consistent coloring on edits, and circulate an updated draft and the summary materials in advance of the next meeting.