2024 Bond Bill: Accessory Dwelling Units by Right, Explained

An ADU is a housing unit that is separate from the main house, either as a standalone structure or a totally separate part of the main house. It has a bedroom/sleeping area, a kitchen and a bathroom, and is on the same lot as the main house. This ADU must follow zoning setback and parking requirements.

The ADU must have a separate entrance. This can be directly on the outside of the building, or, for attached units, may be inside the main housing unit, as long as it meets the building code’s safety standards.

The ADU’s square footage cannot be more than half of the total square footage of the main house, or more 900 square feet, whichever is smaller. Examples: A 2,000 square foot main house cannot have an ADU that is more than 900 square feet. A 1,200 square foot main house cannot have an ADU that is more than 600 square feet.

Cities and towns can have more restrictions for ADUS, such as maximum size or whether short-term rentals (such as Airbnb) rentals are allowed. However, cities and towns cannot “unreasonably restrict” ADU construction or rental of an ADU as long as they are not short-term rentals. What counts as an “unreasonable restriction”? This is vague and leaves the statute open to interpretation and perhaps litigation from towns that do not like or want ADUs.

ADUs in single-family zones are now permitted by right. Cities and towns cannot ban ADUs or make property owners get special permits to construct them. They also cannot have bylaws that ban property owners from renting out their ADUs. (This should remove the family-only restrictions that some municipalities have for ADUs.) However, duplex or higher zoning areas are not granted ADUs as of right. Your individual city or town may already have rules governing ADUs on these properties.

However, cities and towns can impose “reasonable regulations.” Property owners must adhere to regulations about their septic system’s capacity if they have a septic tank (310 CMR 15, or “Title 5”). They may need a site plan review, and may have to follow their town’s rules about setbacks, the “bulk” or “envelope” of the structure, and its height. They may also have to follow certain restrictions surrounding short-term rentals.

The owner does not need to live in the main house or the ADU to be allowed to construct or rent out an ADU.

If your property is more than half a mile away from a commuter rail station, subway station, ferry terminal or bus station, your city or town can require you to have one additional parking space for your ADU, but no more. If you are closer than half a mile to any of these commuter stations/terminals, the city or town cannot make you construct extra parking for your ADU. Does a bus stop count? Probably not, but we’re not sure. If the intent is to exclude properties near bus stops, then the law has been poison-pilled; One could use a bus stop to commute to a bus station, or other transit station, and not need a car.

If you want to have more than one ADU on your property in a single-family zone, you will need a special permit from your city or town. It is unclear from this wording whether you would also need a special permit to rent out that second ADU. Make sure you know how your municipality is planning to interpret this law regarding rentals before moving forward.

EOHLC can make guidelines or rules if necessary so people can build ADUs under this new regulation.

At time of writing in summer 2024 we had not yet seen the regulations. These will serve as the first interpretation of the law, and we will analyze those when they appear.