A new state law that went into effect on Sunday allows property owners across Massachusetts to build accessory dwelling units, or ADUs — small, secondary homes that may be attached or detached from their main single-family house.
The homes, sometimes known as “granny flats” or “in-law apartments,” are a way of creating new, affordable living spaces for family members or rental income. The state hopes the new law will increase the housing supply, bringing down the high cost of housing throughout Massachusetts.
“By allowing homeowners the freedom to create an Accessory Dwelling Unit, we can provide more housing options for seniors, creating opportunities for young adults with special needs looking for more independence and developing smaller, more affordable, housing options for our state,” Gov. Maura Healey said in a statement Monday.
But what qualifies as an ADU, and how can homeowners take advantage of the new regulation?
What is an ADU?
Under state law, an ADU is a secondary housing unit with a separate bathroom(s), kitchen, bedroom(s) and a separate entrance from the primary home on the property. They are limited to half of the gross floor area of the principal home on the property or 900 square feet, whichever is smaller.
Because they are small, they are typically an affordable form of housing both to construct and inhabit.
Many homeowners use ADUs as housing for older or disabled family members or for young adult family members moving out for the first time. They might also create an ADU for rental income.
Some ADUs are built as an addition to a single-family house or as a detached dwelling elsewhere on the property. Others are turned into livable space by converting a garage, basement or other parts of the home.
Modular homes are another ADU option. These structures are manufactured in a factory or off-site and can be delivered fully constructed, or all of the components can be purchased as a kit and constructed on-site.
Where are ADUs allowed?
Massachusetts’ new law, which was included in the $5.1 billion housing bond bill signed into law last year, blocks local governments from prohibiting ADUs in any area zoned for single-family homes. The law applies to almost the entire state, with the exception of Boston. (See below)
“Previously, if a homeowner wanted to build an ADU for an aging parent, they would have had to apply for special permits and variances, which in many cases can be outright denied due to restrictive zoning bylaws,” said Housing and Livable Communities Secretary Ed Augustus. “Now, ADUs are allowed by-right statewide, making it easier for residents to build in their own backyards or onto their existing homes.”
Cities and towns can still regulate new ADUs through their regular local planning approval process, but they cannot unreasonably restrict their construction. In general, design and dimensional standards that would not also apply to a single-family home in the applicable district cannot be used to limit ADUs.
Towns cannot require more than one additional parking space if the property is beyond a half-mile of a public transit station or require any additional parking spaces if it is within a half-mile of a station.
Municipalities also cannot require separate utility connections and may not make applications subject to site plan review or impact analyses that would not also be required for a single-family home.
For more information about the law, visit the state webpage.
What do I need to do to get my ADU approved?
While the new state law allowing ADUs by right is now in effect, individual cities and towns will still have different processes for approving new building projects, and they may not yet have established zoning to explicitly allow and regulate ADUs. Check with your local government to find out more about the specific design requirements and application process for your town.
However, most municipalities will require plans and designs to be submitted to the planning or building department to ensure they comply with other zoning and design requirements. Property owners may also have to get approval from an environmental review board or historic district, depending on where the property is located.
Before beginning construction, the property owner must acquire all of the necessary building permits, as with any other construction project.
Can I rent out an ADU?
Property owners can rent out their ADU, either to long-term tenants or, in some cases, as a short-term vacation rental. They can provide a good opportunity for rental income, and local governments cannot require that ADUs be occupied by the property owner.
However, there may be restrictions on short-term rentals in specific communities.
Under the new law, towns cannot outlaw the use of ADUs as short-term rentals if they do not also regulate the use of other homes as short-term rentals. Some local governments do limit or prohibit short-term rentals, so homeowners should check the laws where they live before listing their ADU as a vacation rental on platforms like Airbnb or VRBO.
What if I live in Boston?
The new statewide ADU law does not apply to the city of Boston, which has many different zoning rules from the rest of the state. However, the capital city is currently working on updating its zoning code, including making it easier to build ADUs.
Last year, the city launched its ADU Guidebook, which provides guidance for homeowners interested in building one of the housing units on their property. The guidebook provides example designs for various lot sizes as well as information on the application and review process and financing options.
