(ADUs) across the state has led to a surge in permit applications and issuances at the municipal level, but the overall production of what are also known as granny flats remains hampered by an overly complex regulatory system, a new report says.
The report, released Wednesday, comes from Boston Indicators, the research arm of the Boston Foundation, and Abundant Housing Massachusetts, an advocacy group that has thrown its shoulder into the YIMBY (Yes in My Backyard) movement.
The ADU mini-boom – an “immediate uptick at a scale of hundreds of homes” – is the result of the 2024 Affordable Homes Act, which took effect in February 2025. It helped lead to 1,600 permit applications and more than 1,200 permits issued, indications of high demand, the report said. A previous study from 2018 showed 100 Greater Boston cities and towns permitting them at an annual average of 2.5 ADUs per community.
But the 2025 numbers still fall short of the production that’s needed as the state faces a housing crisis in which demand outpaces supply. The Healey administration has promoted a goal of more than 220,000 new units of housing over the next decade. Administration projections had suggested legalization would lead to 8,000 to 10,000 homes in five years.
The report offers two takeaways: First, state-level housing reforms – which have drawn some grumbling and legal action from municipalities that want to hold onto control through local regulations – can accomplish “more in one year than 50 years of local reform did.” Second, the next step is to go beyond zoning reforms geared towards increasing housing production.
“A comprehensive agenda is needed to address regulatory barriers to housing production, spanning building, fire, energy, septic system, wetlands, and stormwater rules,” the report said. “The barriers include the fragmented complexity of the regulatory system itself.”
The state’s ADU regulations, which drew disagreements on a quieter level than the MBTA Communities Act, still took municipal authority into account, creating confusion given how many local requirements there are, according to the report. And like the MBTA Communities law, Boston is exempted from the statewide ADU legalization, and is carving its own, slower path.
Boston still led the list of communities that permitted the most ADUs last year: City Hall took in 69 applications and 44 permits. Plymouth was next (42 applications and 34 permits), followed by Lawrence (44 applications and 32 permits) and Nantucket (27 applications and 27 permits).
The report suggested regionalization of permit review processes: “Massachusetts has 351 cities and towns, most of them small, each with its own staffing, boards, inspection schedules, logistical demands, and informal enforcement norms. Many municipalities lack the staff and technical expertise to run the project reviews, especially if permitting activity were to pick up. Franklin County offers a model of regionalized permitting.”
The report was the result of ADU builders, architects and homeowners who took matters into their hands, or are considering building one. Advocates, attorneys, local officials and state agency staffers were also interviewed.
An online event presenting the report’s findings, led by Boston Indicators’ Amy Dain, is scheduled for 9:30 a.m., with a panel discussion to follow. The panel includes Meredith Boericke of the Massachusetts Housing Partnership, Chris Lee of construction company Backyard ADUs, and Claire Morehouse of the Executive Office of Housing and Livable Communities.
California, which first adopted ADU changes in 2016 and then took on additional reforms has us beat: 150,000 permitted over the last decade, and 80,000 built in the same period, per the Boston Indicators report. What’s your take on the report? Send it along here: gin@massterlist.com.