Accessory Apartments in the Great Neighborhoods Bill

The Boston Sunday Globe ran a feature on the front page of its Real Estate section this past week titled, “Can In-Law Apartments Help Ease the Housing Crisis?” and cited a State House bill—our Great Neighborhoods bill—that would establish some statewide rules for accessory apartments.

Sign our online petition supporting Great Neighborhoods legislation.

Let’s take a look at what these “accessory dwelling units” (or ADUs for short) are and what they might look like. Then I’ll explain the ADU provision included as one piece of the development reforms included in the Great Neighborhoods bill.

Accessory apartments are modest-sized housing units that belong to the same property as its main home. This could take the form of a basement apartment, an in-law suite, a converted garage, or a “tiny home” in the yard.

The idea was widely practiced in the past, and it is coming back strongly as young people look for housing they can afford in desirable communities where single-family home prices are out of their reach; and also for older homeowners who want to stay where they are but would like a family member, caretaker, or simply a renter to help make that possible. It’s an invaluable form of housing for disabled family members who want to live independently but with support nearby.

The beauty of ADUs is that it allows homeowners to contribute to solving our housing crisis while doing something that helps make ends meet and ultimately increases the value of their property. It’s a win-win.

Additionally, it’s a tool that costs the government no money and creates affordable units without subsidy. ADUs allow incremental growth that fits snugly into single-family neighborhoods, with designs that are unique and customized.

It’s an idea that’s catching on in Massachusetts. The City of Newton, for example, passed an accessory apartment ordinance this April that will make it a real option for many single-family homeowners in that community.

However, there are 351 cities and towns in the state, and large numbers of them don’t allow ADUs at all, or have many rules that restrict their use.

That’s where our Great Neighborhoods proposal comes in. Passing a local ADU ordinance is hard, and requires a super-majority—generally two-thirds—of the City Council, Board of Selectmen or Town Meeting to approve. Rather than have 351 fights across the Commonwealth, the proposed legislation (House Bill 2420 and Senate Bill 81) would establish consistent minimum standards across the state. Yet each community would be able to tailor its own local rules in important ways.

The Great Neighborhoods proposal would allow property owners the right to build an internal accessory apartment within their single-family home on lot sizes of 5,000 square feet and larger. There must be a separate entrance to the unit from the outside or the inside of the home, and it shall not be sold separately from the main home.

The municipality may require owner-occupancy on the premises and may also cap the total number of ADUs at 5% of the community’s total housing units. Finally, the ADU may be no larger than 900 square feet and no more than one additional parking space may be required.

And that’s it! If the municipality wants to create additional rules to allow freestanding ADUs, they are free to do so at their discretion.

This provision was widely and intensely debated during last year’s State Senate debate on the bill, and we believe that most people were satisfied that the result is a fair compromise that makes this tool available to all cities and towns while respecting local authority.

Sign our online petition supporting Great Neighborhoods legislation.

We welcome your thoughts. Feel free to reach out to me at

Other resources and articles:


How Cities Get “Granny Flats” Wrong (City Lab)

Are Accessory Dwelling Units Allowed in Your Town? (Strong Towns)

ADUs: A Flexible, Free-Market Housing Solution (Strong Towns)

André Leroux is the Executive Director of the Massachusetts Smart Growth Alliance.

Recent Posts


Search By Tags

Join US

Follow Us

  • Black Facebook Icon
  • Black Twitter Icon
  • Black Instagram Icon
  • LivableStreets Facebook
  • LivableStreets Twitter

LivableStreets Alliance    

70 Pacific Street, Cambridge, MA 02139

P: 617.621.1746      E: