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Expanding ADU Access in Boston

We want to streamline the process for homeowners looking to create an additional unit.

The Additional Dwelling Unit (ADU) is a self-contained residential living unit. They can provide additional income for homeowners and flexible, separate living arrangements for families to age in place, or support relatives or children while still maintaining their privacy. 

To demonstrate what is possible and learn what barriers residents face, we conducted pilots and demonstration projects. This work led to zoning relief for ADU 1.0 (building an ADU within the footprint of your home). We are continuing work to expand ADUs to include backyard units. To stay up to date on the future of the ADU program, sign up for our email list.

ADU Program Background

Program Background

Lack of affordable housing is a significant concern for many Boston residents. ADUs provide an opportunity to add housing without changing the character of the residential fabric. 

In addition, ADUs help homeowners remain in their homes by generating steady rental income, support multigenerational family arrangements, and provide opportunities for aging in place. 

Our goal is for ADUs to:
  • Increase affordable housing options in Boston neighborhoods
  • Use existing infrastructure to achieve the City’s housing goals
  • Support homeowners to remain in their homes by generating steady rental income 
  • Support multigenerational family arrangements 
  • Provide opportunities for aging in place

The Housing Innovation Lab and Mayor’s Office of Housing have launched a few pilot and demonstration projects that have expanded the public discourse about ADUs in Boston, helped uncover barriers for residents that want to create an ADU, and created opportunities for streamlining the process. 

ADU 1.0 (Nov 2017- May 2018)

The ADU 1.0 Pilot allowed owner-occupants of 1-, 2-, and 3-family homes in East Boston, Mattapan, and Jamaica Plain to carve out space within their home to build an ADU. 

In under 12 months, the pilot program worked with over 50 eligible applicants as they moved from ADU design to construction. ADU pilot applicants ranged in age, income, race, and ethnicity. 

Within the first year of the pilot, 12 applicants received building permits and two residents completed construction. The success of this Pilot led to expansion of the Zoning Amendment to the remaining Boston neighborhoods. 

Read more about the ADU 1.0 Pilot

Plugin House (May 2018)

The Plugin House, an easily assembled compact unit, was placed on City Hall Plaza in May 2018. The exhibit welcomed over 2,000 visitors in a one week period. Comments collected from visitors overwhelmingly supported allowing this type of housing in Boston. 

Read more about the Plugin House

ADU 2.0 (2021-2022)

The ADU 2.0 Pilot provided support to homeowners interested in turning existing exterior structures—like carriage houses and underutilized garages—into livable space. 

In 2021 and 2022, we hosted two cohorts with eight residents each. We worked with these homeowners to understand the barriers, gaps, and opportunities to create ADUs in existing exterior structures. 

Over the course of four months, participants were offering technical assistance through three workshops to help them through the process of preparing and submitting a long form building permit with Inspectional Services, and requesting variances (if needed) from the Zoning Board of Appeals. Learnings from these cohorts are helping to push regulatory change to allow backyard ADUs by right in Boston

We frequently hear from residents who want to build ADUs external to the main building, either as attached (additions) or detached structures (backyard cottages). 

The current zoning relief only applies to internal ADUs (mostly basements and attic renovations). We are working to expand ADUs zoning relief, financing tools, and development support to help more homeowners access this opportunity.

Sign up to stay up to date

To learn how to move forward with the process of adding an interior ADU to your property and how to apply for a 0% loan to build your approved design, visit the ADU Program webpage.

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