All Towns Laws for Accessory Dwelling Units (ADUs) in Massachusetts

By Kimberly Rau, MassLandlords, Inc.

ADUs represent the biggest new investment opportunity for small investors in Massachusetts. In October 2023, the Department of Housing and Urban Development (HUD) announced that forecast rental income from accessory dwelling units (ADUs) could be used when calculating a potential homeowner’s income when applying for mortgage financing. This creates an opportunity for small investors looking to expand existing buildings. But which cities and towns in Massachusetts allow homeowners to have an ADU in the first place?

Accessory Dwelling Units (ADUs) are being tried in many cities and towns. Some allow investors and no special permit. Derivative of Licensed 123rf.com.

What are Accessory Dwelling Units (ADUs) in Massachusetts?

Accessory dwelling units, also called ADUs, accessory apartments, in-law apartments, granny flats and accessory residential units, have been a hot topic of conversation over the past few years, and with good reason. ADUs can increase housing supply. They also allow homeowners to get a little extra rental income. They can help elderly homeowners remain in their home longer. Or they can allow younger generations to stay in the town they grew up in without having to pay a high mortgage.

When we started researching accessory dwelling units, we realized that there is nowhere online where you can find a list of all the cities and towns in Massachusetts that allow them. There were several lists, but they were incomplete and out of date (one list we found was 18 years out of date). Many towns have changed their ADU policies. We couldn’t find a single resource that told us what we wanted to know: Which towns allow ADUs? Is owner occupancy a requirement? Are ADUs allowed by right, or by special permit? Are they allowed to be rented out, and if so, must the tenants be related to the homeowners?

How We Got the Massachusetts ADU Ordinance List

Necessity is the mother of invention! We have many member housing providers who might want to build an ADU, but there was no clear way to find the rules. So we made the list ourselves. We looked up zoning bylaws and read newspaper articles about proposed ordinances. When we couldn’t find the answers online, we emailed planning boards, zoning boards and town clerks. We learned that some local governments either do not receive or answer our emails (those would be the handful of incomplete entries we are hoping to update as soon as possible). Our intent is to update this list as laws change.

What Does the List of ADU Laws Show?

The results are complicated. Massachusetts has 351 cities and towns, many of which allow accessory dwelling units in some form. The rules vary widely. Our comprehensive ADU policy list includes all major types of restrictions. Some municipalities allow only certain kinds of units. Some cities make homeowners apply for a special permit to create any kind of ADU, others allow for construction by right (you’ll still need a building permit, though). Some condition permission on whether the ADU is attached or detached. Certain town bylaws state only family members can occupy an ADU. Others state the unit cannot be rented out. Almost all zoning bylaws require that either the main unit or the ADU be permanently owner-occupied. We include links to each area’s specific bylaws so you can see for yourself. If bylaws are unclear or not available online, we provide the source where we found our information.

There are very few cities and towns in Massachusetts that allow ADUs for investors who don't owner-occupy. At publication of this article, only 14 do not specify that the property owner must live on-site. Many of those are on the Cape (or Martha’s Vineyard). There may be others, but a handful of towns have not confirmed this as of this article’s publication. That said, you can be an owner-occupy landlord! Many of our members are.

Some areas do not allow ADUs at all, but those areas are relatively few. Several have proposed ordinances seeking to change that. When researching our ADU policy list, we consulted lists that were curated some time ago. We are pleased to note that many of the municipalities that did not allow ADUs back in the early 2000s have since changed their policies. We will keep this list updated, but if something changes in your town, please let us know. You can email us at hello@masslandlords.net or (if reading this on our site) use our feedback widget a lower right.

Members-Only ADU Laws by Town and City