City of Boston Announces New Tools to Assist Residents in Building Accessory Dwelling Units (ADUs)

The City of Boston today announced a new program to support Boston homeowners in building Accessory Dwelling Units (ADUs) on their property. This initiative, administered by the Boston Home Center (BHC), a division of the Mayor’s Office of Housing, offers a new bank loan option alongside grants and other financial assistance to help cover costs related to designing, permitting, and building an ADU. Additionally, the Planning Department is releasing an Accessory Dwelling Unit (ADU) Guidebook, an illustrated manual that will help property owners in Boston who may want to build an ADU on their property. This book is available online, and in all Boston Public Library branches. Building on the Mayor’s leadership to make Boston a home for everyone, these steps are important to increasing the City’s multigenerational housing stock, keeping families together and building wealth.

"Accessory Dwelling Units are a powerful tool in our efforts to address the housing crisis in Boston," said Mayor Michelle Wu. "By creating more flexible and affordable living options, ADUs allow homeowners to maximize their property while contributing to the availability of housing in our neighborhoods. This initiative not only supports families looking to generate extra income or house loved ones but also strengthens our communities with more diverse and accessible housing choices."

Through the loan programs, the BHC provides income-eligible owners of 1-3 unit homes who plan to add an ADU with a Technical Assistant Grant of up to $7,500. This grant provides eligible homeowners with targeted funding and staff guidance throughout the pre-construction phases of researching, designing, and permitting their ADU. Additionally, homeowners can apply for an ADU Loan from the City of up to $50,000 to support construction costs. The ADU Loan carries 0% interest and is deferred, meaning there are no monthly payments. Homeowners approved for this program are paired with a BHC Construction Specialist who monitors progress throughout the building process. Eligible homeowners who receive an ADU Loan may also explore additional financing opportunities with participating lenders. To qualify for the program, applicants must meet specific income and asset limits. 

“Accessory Dwelling Units are an important part of our strategy to expand housing options in Boston,” said Sheila A. Dillon, Chief of Housing. “ADUs give homeowners a way to create additional living spaces that can serve as a source of income, provide housing for family members, and help address the city’s housing needs. By making it easier to build ADUs, we are supporting residents, increasing housing supply, and strengthening neighborhoods.”

As part of this effort, the City is also piloting a new ADU Bank Loan in partnership with local banks, Leader Bank, Dedham/Southshore Bank, Needham Bank, and the Cooperative Bank. Recognizing the challenges posed by construction expenses, the Boston Home Center and the Mayor’s Office of New Urban Mechanics initiated a collaboration with Harvard’s Laboratory for Values in the Built Environment and local lending institutions to develop innovative solutions that ensure low- and moderate- income homeowners can access the unique benefits ADUs provide. This resulting loan fills a gap in the market, providing affordable financing to cover construction costs associated with building ADUs. 

“Our research shows that homeowners need new loan products to meet the unique opportunity that rental ADUs can offer homeowners, and provide equitable access to ADU financing,” said Charu Singh, Research Associate at the Laboratory for Values in the Built Environment at Harvard GSD. “I’m proud of the groundbreaking work our group has done to equitably expand the lending toolbox, especially during this time when Boston is struggling with too few housing options and high costs.”

Building on Mayor Wu’s commitment to remove barriers to building ADUs across Boston’s neighborhoods, the ADU Guidebook is designed to provide homeowners with practical guidance and inspiration for adding an ADU to their property, whether it is for additional living space, rental income, or housing family members. The ADU Guidebook features realistic, buildable designs tailored to Boston’s neighborhoods. Although the designs will still require permits and may need review by the Zoning Board of Appeal, they offer a clear starting point to help residents more easily move forward with their ADU. It will be available online and at all Boston Public Library branches.

“This Guidebook is a fantastic starting point for anyone looking to add another unit to their home, and we hope it will inspire people to see ADUs as an expedient and unique way to add to our housing stock,” said Chief of Planning Kairos Shen. “I look forward to working with the community on new complementary zoning that will make the process of adding an ADU more flexible and affordable.” 

These initiatives align with the City’s broader zoning reform efforts to enable more housing options across Boston. By updating zoning regulations, the City aims to break down barriers and foster flexible housing solutions. ADUs not only help increase the housing stock but also offer residents opportunities to age in place, provide extra space for growing families, or generate rental income. ADUs can help residents stay in their neighborhoods, adapt their homes, and address their evolving needs. By allowing various forms of ADUs, the City aims to help homeowners fully utilize their properties, create more space, or unlock new income opportunities.