Massachusetts embraces backyard homes as housing and climate solution

Massachusetts homeowners are getting new help to build accessory dwelling units, or ADUs — small backyard homes, garage apartments, or in-law suites. A 2024 state law made ADUs legal in nearly every city and town (Boston is the exception) and limits how much local rules can restrict them, though towns can still set their own property-line setbacks, septic rules, and height limits. In 2025, over 1,200 ADUs got permits statewide, still short of the state's goal of 1,600 to 2,000 a year through 2030.

Two new programs aim to make the process easier. The Massachusetts Housing Partnership connects homeowners with providers who charge no more than $500 for a feasibility study covering zoning limits, utility needs, design, and a rough cost estimate. Building an ADU typically runs $120,000 to $450,000, depending on size and whether it's new construction or a conversion. The Massachusetts Clean Energy Center offers a free online tool, the ADU Wizard, that lets you look up your own property, see whether an ADU could work there, and test different layouts. In the Pioneer Valley region of western Massachusetts, a separate program offers one-on-one guidance and a list of manufactured-home suppliers. The state also introduced a low-cost financing program for ADUs in March.

Beyond adding housing, many ADUs are built all-electric and highly efficient, some using factory-built, airtight construction, which can mean lower energy bills. If you're considering one, your town's specific zoning rules will still shape what's possible on your property.