The Hampden Planning Board held a public hearing April 16 on proposed revisions to the town’s accessory dwelling unit (ADU) bylaw to ensure consistency with recently published state regulations.

The revisions are intended to implement state limits and definitions rather than create a new local policy. Board members discussed how to compute gross floor area when multiple principal dwelling units are present, the state’s maximum ADU size rules, parking requirements tied to transit proximity, and whether the town must allow more than one ADU on a lot.

Why it matters: ADU rules affect homeowners’ ability to add one or more secondary living units on their property, with implications for housing supply, property configuration and infrastructure like parking and septic capacity. State regulations give a minimum set of rights that communities must allow; municipalities may not adopt rules more restrictive than state law.

Key points from the discussion
- Gross floor area (GFA): The board examined the state definition of GFA and confirmed that when multiple principal dwelling units exist on a lot the GFA used to compute maximum ADU size is the largest principal dwelling’s GFA, not the sum of all units. The board clarified application in two‑family houses and “double‑decker” arrangements.
- Maximum ADU size: Under the state regulatory language discussed at the hearing, an ADU “shall be no larger in gross floor area than half the gross floor area of the principal dwelling unit or 900 square feet, whichever is smaller.” The board discussed consequences for very small principal dwellings and concluded that the draft language follows state limits.
- Parking and transit exceptions: The draft includes a parking provision that would waive an additional parking requirement if the lot is outside a half‑mile transit radius; board members noted that the waiver language references MBTA‑style rules and is not applicable to Hampden and suggested simplifying or removing that transit exception from the local bylaw text.
- Multiple ADUs: The board reviewed state guidance that one protected ADU must be allowed as‑of‑right and that communities do not have to permit more than one ADU; the board agreed to strike language implying that multiple ADUs must be allowed and to retain the option of allowing additional ADUs by special permit.

Process and next steps
Board members identified several editorial and technical comments from town counsel and other reviewers that staff will incorporate (for example, removing redundant phrases, clarifying which measurements apply to which dwelling types, and cross‑referencing existing height and dimensional rules). The board plans to reconvene after staff incorporate counsel’s comments and will then make a recommendation to the select board and to town meeting as appropriate.

No final vote on the bylaw changes occurred at the April 16 session; the hearing was closed for Case 2025‑C and the board scheduled a follow‑up meeting to consider revised language prior to forwarding a recommendation.