What's an Accessory Dwelling Unit? They may help the housing crisis in Massachusetts
Big problems don't always need big solutions. In Massachusetts, one of the answers to the housing crisis might be hiding in the backyard. They're called Accessory Dwelling Units, or ADUs for short.
Think of them as pint-sized homes, built on the same lot as an existing home. Once upon a time, these little homes were locked down by zoning rules, you could build one, but only if a relative was moving in. Renting to anyone else? Off limits. But now, building an ADU has become much easier.
For Linda and Mark Adler of Lexington, the solution to their own personal housing crunch didn't just fall from the sky, but it did get slowly lowered from above.
Their new ADU was delivered in a couple of massive prefabricated pieces. A crane gently set them down in the side yard. Just like that, they had a brand new, two-bedroom, two-bathroom, 900 square foot home.
"Two big pieces, on two flatbed trucks and an enormous crane lifting both pieces over our existing house," said Mark. "Which was a little scary."
The Adlers added the ADU when their daughter and grandkids moved in. Now, they're living just steps apart, with much more room to breathe.
"For us it was an affordable solution to being close, but giving everybody space," said Linda.
About 30 miles away in Northboro, Marsha Gleason built her own ADU in the backyard of the house she once shared with her late husband.
"My new home is just perfect for me," she said. "It has allowed me to stay in my neighborhood."
Now, her son and daughter-in-law live in the main house. Marsha's 800-square-foot home is filled with her artwork and she still hosts her friends and the occasional sleepover for her grandkids.
"I've had groups here," she said. "I can still entertain."
Accessory Dwelling Units in Massachusetts
Until recently, ADUs were nearly impossible to build in many Massachusetts towns, thanks to zoning restrictions and red tape. But that changed in August 2024 with the Affordable Homes Act.
What's new? Well, there are no more special "ADU permits." No more rules about ADU's being for "relatives only." Now, you can build an ADU that's up to 900 square feet in size. It can be inside an existing home, attached, or completely separate, as long as it has its own entrance. You can also rent out an ADU.
"We had a patchwork of regulations across Massachusetts, 351 cities and towns. Some you could build ADUs relatively easily, some you couldn't build them at all," said Ed Augustus, Secretary of Housing and Livable Communities. "Now, ADUs are one way we're tackling the housing crisis."
Augustus estimates 8,000 to 10,000 ADUs will be built in the next five years. But that's just the start. The state says Massachusetts needs about 200,000 new housing units over the next decade to truly get ahead of the crisis. ADUs are just one piece of the solution.
Before you start sketching your backyard floor plan, there are a few caveats. Property taxes may go up.
Adding an ADU increases the value of your property, and likely your tax bill. Towns can still pass rules banning ADUs from being used as Airbnbs or other short-term stays. You'll need to follow setback rules and other basics, even under the new law.
How much do ADUs cost?
Chris Lee runs Backyard ADUs, a company that builds these units off-site and installs them in a matter of months. The average price of one of his homes is around $300,000. They can run as much as $500,000. But the new laws are making ADU's more popular.
"It's getting easier," Lee said. "Vermont was the first state in New England, Maine followed, Rhode Island followed, Mass. followed and now New Hampshire just followed. Basically New England is catching up with the West Coast."
For some families, these small homes are delivering a big solution. For them, an ADU is A-OK.
For more information on the state's new rules on ADUs visit Mass.gov.
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