Backyard Apartments Now Legal Across MA: What To Know

MASSACHUSETTS — State leaders are celebrating Gov. Maura Healey's signing of a sweeping new housing bill Tuesday that contains $5.1 billion spending authorizations, but also law and policy changes that could change the state's housing landscape.

One key piece of the law allows accessory dwelling units, also called in-law apartments, by right in every community in the state in single-family zones. ADUs can come in many forms, including basement and attic apartments, additions onto existing homes, or small cottages separate from a main home.

Under the law, ADUs will not need local zoning approval as long as the units are the smaller of either 900 square feet or half the square footage of the primary home. Local laws on short-term rentals, like Airbnbs, will still apply, but "no municipality shall unreasonably restrict the creation or rental of an accessory dwelling unit," the law says.

Some communities in Massachusetts have ADU laws that require occupants to be related to the property owner — a tricky limit that can be hard to monitor and enforce. The state law does not have that restriction, and allows ADUs on properties not occupied by the owner, as long as the ADU only has one parking space allotted to it. ADUs within a 1/2 mile of transit stations do not have to have any allotted parking spaces, the law says.

The law also contains a $60 million authorization for a program to help homeowners build housing — including ADUs — for people with disabilities and elderly people who need daily assistance.

ADUs have only been partially legal in Massachusetts after zoning changes in individual cities and towns — including some that came after tense debates over regulating accessory units. In 2023, Worcester took nearly a year to pass an ADU ordinance that restricted them to only properties occupied by the owner. Even then, the measure did not pass the city council unanimously.

Lawmakers believe the law change lead to the construction of between 8,000 and 10,000 ADUs across the state over the next five years.