Not including Boston, the state’s largest city by far, Lowell tops the list of cities or towns with the most approved Accessory Dwelling Units (ADU’s), according to information released today by the Healey-Driscoll Administration.

In all, 2,084 such projects have been approved since the beginning of 2025, with the Mill City leading the way at 53 ADU’s approved. Sommerville is second at 50 such units. Lawrence, our Mill City neighbor to the north is fourth with 46.

The pace of approval has picked up significantly in the most recent calendar year, with 854 approvals granted over the first half of 2026, well above the pace of last year’s 1,230 approved units. (click here to view the reported list on Massachusetts’ official website)

Governor Maura Healy trumpeted the data, stating “we wanted to make it easier for homeowners to build ADUs because we knew they were an effective tool for building the type of housing people need and lowering costs. We’re seeing homeowners across Massachusetts take advantage of this new opportunity, whether it’s creating space for aging parents, helping adult children stay close to home, earning rental income or adding another home in their community. We’re working to build on this early progress by giving homeowners more of the practical tools they need to get these projects built.”

ADUs, also known as in-law apartments, are small, independent homes located on the same lot as another home. They may be created within an existing home, built as an addition or constructed as a separate structure. ADUs can provide space for aging parents, adult children, caregivers or people with disabilities. They can also provide homeowners with supplemental rental income and add new rental opportunities within existing neighborhoods.

To date, 70% of the state’s 351 cities and towns have granted approval for at least on ADU.