Massachusetts Court Affirms: Separate Sewer Connections for ADUs Cannot Be Mandated
At this year’s Massachusetts Housing Partnership (MHP) 18th Housing Institute, held June 4–5, 2025, in Worcester, housing professionals and municipal leaders gathered to chart the future of housing in the Commonwealth. One of the most impactful developments discussed didn’t come from a new policy or legislative announcement—but from the courts.
During the breakout session, “From Policy to Practice: Understanding & Implementing the Commonwealth’s ADU By-Right Law,” legal experts and planners highlighted a major judicial ruling that reshapes how towns and cities approach accessory dwelling unit (ADU) regulations: a Massachusetts court has ruled that municipalities may not require separate utility connections—specifically sewer lines—for detached ADUs.
The Court Decision That Changes the Game
The ruling stems from a case that challenged local zoning bylaws requiring all detached ADUs to install independent sewer hookups, regardless of site context or capacity. The court found these requirements to be in violation of state law, specifically 760 CMR 71.03(3)(b)(3), which outlines the implementation of Massachusetts’ by-right ADU law, in effect since February 2025.
According to the regulation, municipalities cannot impose additional permitting or infrastructure requirements unless:
They are required by the regional or local utility provider, or
Mandated by other lawful authority, such as public health or environmental regulations.
The court’s February 2025 decision—now referenced in guidance by the Attorney General’s Office—firmly stated that requiring blanket separate sewer connections is an unlawful barrier to ADU development. The decision also clearly enforces that municipalities cannot require extra parking, or require attached ADUs only, or disallow ADUs to be added to lots with more than one existing structure.
What This Means for Municipalities
For local officials, planners, and permitting staff, this ruling is a wake-up call. Towns that currently require separate sewer or water connections for ADUs—especially in their zoning or Board of Health regulations—must now amend those rules to align with state law. Failure to comply may result in Attorney General disapproval or legal challenge.
As panelist Margaret Hurley, Senior Counsel for Housing and Municipal Law at the Attorney General’s Office, emphasized: municipalities may tailor design and development standards to local needs, but cannot create financial or regulatory burdens that block the intent of state law—namely, to make ADU development simple, predictable, and affordable.
Why It Matters
Sewer connection requirements often cost thousands—sometimes tens of thousands—of dollars. Eliminating this barrier not only makes ADUs more feasible for average homeowners, it helps fulfill the law’s broader mission: unlocking gentle density and increasing housing supply without displacing community character.
As Massachusetts grapples with rising housing costs, aging populations, and shifting household needs, small legal and policy victories like this one play an outsized role. The message is clear: the Commonwealth is committed to making ADUs an accessible, practical option—and municipal red tape won’t stand in the way.
Key Takeaway
The Massachusetts court ruling affirms that municipalities cannot require separate sewer connections for detached ADUs unless mandated by a utility or lawful authority. This decision removes a significant cost barrier and strengthens the foundation of the state’s by-right ADU law, empowering more homeowners to build and benefit from accessory housing.
The court also ruled on several other cases that challenged local zoning bylaws affecting ADU’s which can be found here.
The complete 760 CMR document can be found online here.