Boston is hosting a weeklong public event at City Hall Plaza aimed at inspiring homeowners to consider building a secondary home on their property.
The event features a fully built accessory dwelling unit, or ADU, and giving residents to tour the model. The city is also holding a workshop each day at noon to educate residents on how to design, finance and permit ADUs in Boston.
The event comes as the city, which faces a shortage of affordable housing, works to simplify the process to permit an ADU.
"We all know that ADUs will become easier to build and more abundant if we continue to figure out how to make it easier and cheaper to build ADUs in the city," said Sheila Dillon, the city's chief of housing. "We know that it's going to increase our housing supply in the way that our neighborhoods really welcome."
An is an independent living unit that can be built inside of an existing home (by converting a basement or an attic into a separate unit) or else outside of a home, such as in the backyard.
A single box ADU — the kind being showcased on City Hall Plaza — is roughly 450 square feet and has one bedroom. Those units start at $210,000 and take between six and 10 months to build.
Dillon said ADUs were initially built as "in-law apartments," allowing older adults and parents to live close to their adult children. But now, the range of uses has expanded.
"Now, as housing costs continue to be too expensive for many, it's becoming a resource for adult children who no longer want to live in their childhood bedroom but want to stay in the communities that they love and they grew up in," she said.
In 2024, Gov. Maura Healey signed a housing bond bill that legalized ADUs on most single-family lots in the state as one way to help chip away at Massachusetts' housing shortage.
The rule gives communities room to enforce some "reasonable restrictions," including setback requirements from property lines, which create challenges for builders.
Those differences across municipalities can complicate the permitting process for ADUs, often drawing it out.
Chris Lee, the president of , said his company has built nearly 150 ADUs since 2020.
"It's accelerating," he said. "At the end of last year, we got to one a week, and we're hoping by the end this year, to be at two a week."
Lee said he thinks that ADUs will become a more common housing option in Massachusetts.
"It's just a matter of people coming into the market to be able to build them and permit them," he said. "There's not a lot of backyard ADUs out there, but that will happen. And cost — even at $225,000, it's a lot of money. It's cheaper than everything else, but the more that we can put pressure on costs, and the more the financing catches up, these will take off."
Dillon said she'd like to see ADUs become an important element of its housing supply, and that the city is working to make that happen.
"In some parts of Boston, we do have larger size yards and backyards, and we are looking to really increase the supply of ADUs that are outside the existing footprint," she said. "The planning department is working on zoning reform to make it easier to build ADUs."
The city will hold a resource fair on May 16 where residents can speak directly with lenders, architects, and others involved in ADU development.
The public event will run through Sunday, May 17.
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