New survey data from the Executive Office of Housing and Livable Communities shows that homeowners across Massachusetts are embracing accessory dwelling units (ADUs) following Governor Maura Healey’s Affordable Homes Act, which allows ADUs to built by-right on single-family properties statewide.
ADUs, also known as in-law apartments, are one strategy for building new homes and lowering costs. In the first six months of 2025, homeowners in 170 communities filed 844 applications to build ADUs on their properties, of which at least 550 had been approved as of July 2025.
Before the Affordable Homes Act, Massachusetts had no statewide standard for ADU zoning and permitting. A patchwork of requirements including owner-occupancy restrictions, small size limits, subjective design reviews and discretionary approvals often made ADUs difficult to build. Now, ADUs under 900 square feet can be built by-right in single-family zoning districts statewide (excluding Boston, which has its own ADU by-right ordinance).
An interactive map tracking ADU applications can be found at Mass.gov/ADU. Data was gathered from an EOHLC survey of municipal building inspectors between July 9 and Aug. 1, 2025. Application and permitting numbers are for the period of Jan. 1 to June 30, 2025. A total of 242 communities responded to the first survey. HLC will survey municipalities again in January 2026 to assess the first full year of ADU activity and to collect more detailed information on location, size and type of ADUs being applied for.
Residents interested in developing an ADU should contact their city or town building or inspectional services departments which will be able to give them an understanding of the local rules and how they can apply for a permit. Additionally, residents seeking to build an ADU for people with disabilities or people over 60 may be eligible for no-interest financing through the state’s Home Modification Loan Program.
Municipalities and age-friendly community partners who need assistance drafting, conducting community planning, and enacting local ADU rules may apply for funding through the Community One Stop for Growth.