The new statute is known as the Affordable Homes Act. The Act is Chapter 150 of the Acts of 2024. The ADU provisions are part of the state’s broader efforts to address its housing affordability crisis and increase housing options, particularly in high-demand areas.

Essentially ADUs are now legal almost everywhere “as of right.” If you’re a homeowner considering adding an ADU or just wondering how this new law affects you, here’s a breakdown of the key features giving you new legal rights and how to proceed.

What is an Accessory Dwelling Unit?

In general, an ADU is a small, self-contained living space located on the same lot as a primary residence. It can take various forms, such as a basement apartment, garage conversion, house expansion, or detached house.

ADUs typically have their own kitchen, bathroom, and separate entrance. Now in Massachusetts they offer flexibility for homeowners to rent out the dwelling unit or use it for family members, such as aging parents or adult children.

Key Provisions of the New ADU Law

The new ADU provisions are Sections 7 and 8 of the Act. Section 7 amends the definition of accessory dwelling unit in the Massachusetts Zoning Act (M.G.L. c. 40A) and is effective now. Section 8 amends Section 3 of the Massachusetts Zoning Act and takes effect on February 2, 2025. These amendments require municipalities to allow ADUs as of right in most residential zoning districts, with some important limitations. Be sure to pay attention to this “small print.”

Do not make any assumptions.

1. “By right” approval: ADUs allowed “by right” means homeowners no longer need special permits or zoning variances to build them (subject to some local regulations). This streamlines the process and makes it more predictable.
2. Size limitations: The ADU cannot exceed 900 square feet or 50% of the size of the primary dwelling, whichever is smaller. This ensures that the ADU remains a secondary, subordinate structure on the property.
3. Reasonable Restrictions: ADUs are subject to reasonable restrictions such as compliance with Title 5 (septic systems), site plan review, dimensional setbacks, bulk and height limits, and restrictions on usage as a short-term rental.
4. No owner occupancy requirement: Neither the homeowner’s primary residence nor the ADU must be owner-occupied. This means the main building and/or the ADU can be occupied by anyone.
5. No off-street parking requirements: In many cases, the law eliminates the need for additional off-street parking spaces for ADUs, particularly if the property is near public transit or in a densely developed area.
6. Flexibility in ADU types: Homeowners can convert existing spaces, like basements or garages, into ADUs, expand existing houses, or construct entirely new structures, providing more options for creating additional housing.
7. Exemptions for certain areas: Some municipalities, particularly in rural or less densely populated areas, may be exempt from certain provisions of the law, though most communities are required to adopt ADU-friendly zoning codes.

Why is the New ADU Law Important for Homeowners?

1. More housing options: ADUs help alleviate the state’s housing shortage by increasing the number of affordable housing options available, especially in suburban or urban areas with high demand.
2. Rental income potential: By building an ADU, a homeowner can generate rental income, which can help offset mortgage payments or provide additional financial security.
3. Flexibility for multi-generational living: ADUs are an ideal solution for families needing extra space for aging parents, adult children, or other relatives, offering privacy while maintaining close family connections.
4. Increased property value: Adding an ADU to a property could increase its overall value. Many buyers are attracted to properties with income-generating potential or additional living space.
5. Supporting sustainable growth: The law encourages the efficient use of existing infrastructure and land by allowing homeowners to build ADUs, reducing the need for sprawling new developments.

What should Homeowners consider before Moving Forward?

While the new ADU law offers many advantages, homeowners should be mindful of several factors before starting a project:

1. Local zoning codes: While the state law sets a framework, municipalities have the authority to establish specific regulations regarding ADUs, such as limits on height, setbacks, or the design of the unit. Check with your local zoning bylaw or ordinance or consult a land use or real estate attorney to understand what rules apply to your area.
2. Building codes and permits: Even though ADUs are allowed by right, homeowners will still need to comply with local building codes and obtain necessary permits for construction. This ensures safety and ADUs meeting all required standards.
3. Health and environmental rules: ADUs must comply with the usual laws about sewerage, water supply, wetlands, storm water, and similar non-zoning requirements.
4. Impact on property taxes: Adding an ADU could impact the property tax assessment. It’s a good idea to consult with a tax professional or local tax assessor to understand how an ADU might affect the real estate tax bill.
5. Financing the project: Constructing or converting an ADU can be a significant investment. Homeowners should plan carefully for the costs and explore financing options, such as home equity loans or construction financing.

Conclusion

Massachusetts’ new ADU law presents a valuable opportunity for homeowners to add housing options to their properties while benefiting from rental income, increased property value, and greater flexibility for family living.

With the “by right” approval process, reduced parking requirements, and flexibility in ADU types, it’s now easier than ever to create an additional dwelling unit on residential property.

However, it’s important to consider the specific zoning regulations in your municipality, comply with building, health, and environmental codes, and carefully plan for the costs of construction.

Consult a land use or real estate attorney, contractor or architect, and others familiar with the law to ensure good advice, careful planning, and proper permitting.

Understand the ins and outs of the ADU law to determine whether an ADU is right for you, your existing house, and your lot.

Then be proud to contribute to the broader effort to make housing in Massachusetts more affordable and accessible.