Despite legalization, obstacles hamper ADU growth in Massachusetts

Although Massachusetts passed a bill last year that encouraged the construction of accessory dwelling units (ADUs) on single-family lots across the state, progress has been slow.

The 2024 law allows ADUs smaller than 900 sf to be built by right on most residential lots, with no need for special approval from local zoning boards. Through the first six months of 2025, the state saw 884 applications for ADUs in 170 communities, with about 550 earning approval. The pace of approvals and projects getting underway is slower than other states that have made efforts to spur ADU construction.

That’s because there are still too many obstacles to getting them done quickly and at an affordable price, according to the CEO of an ADU maker quoted in the Boston Globe. The law still allows communities to have some “reasonable restrictions,” including on setbacks from property lines, that present challenges for builders.

Some towns have conflicting ideas of how an ADU should be connected to a house. Thus, the permitting process for ADUs can still be complicated and drawn out. In some cases, boards still fuss over small details.

Financing is sometimes a barrier, as well. Many more homeowners would be able to afford to build an ADU if the state designed financing products for the units, advocates say.