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Community Impact

Jul 21, 2017

Additional Dwelling Units to increase Boston's housing stock

Adu header

Images courtesy of BSA Staff.

On Thursday, July 13, 2017, 30 designers, developers, builders, and students joined the BSA Housing Committee for an informational session and charrette on the City of Boston’s Additional Dwelling Unit (ADU) pilot program.

This program was presented in partnership with the Mayor’s Housing Innovation Lab (iLab). Marcy Ostberg, director of the iLab, and Claire Summers, one of the iLab’s Summer Fellows, began the evening with a presentation explaining why there is City interest in the pilot program, as well as what does and does not qualify as an ADU under the pilot program guidelines. The pilot program is still in development, and input from BSA members at this charrette will help to shape the final guidelines for the program.

For the purposes of this pilot program, Additional Dwelling Units are defined as smaller, independent rental units created within the existing building envelope of homes with three or fewer units. There are three general typologies of acceptable ADUs in the pilot program: attic units, “carve out” units on existing living floors, and basement units. All units are required to have separate entries from existing units, a secondary means of egress, and conform to all existing City of Boston safety and building codes. To qualify for the program, a home must be owner-occupied and have three or fewer existing units. Short term rental of the ADUs created in the program (such as for Airbnb) is prohibited. Three neighborhoods in Boston will be eligible for the pilot program, though the specific neighborhoods have not yet been chosen.

The benefits of building ADUs range from increasing the number of naturally occurring affordable housing options in Boston’s neighborhoods, to supporting multigenerational family arrangements, to generating additional income for homeowners. The Boston Home Center will provide no-interest home equity loans to homeowners undertaking renovations as part of the pilot program, to help offset renovation costs. Additionally, the Department of Neighborhood Development will provide interested homeowners with an “ADU Creation Toolkit,” which will walk through the process of constructing a new unit. It will explain the details of the permitting process; provide examples, design ideas, and suggestions of designers to work with; and connect residents to financing, including the loan program mentioned above.

Attendees at the charrette were tasked with visualizing how existing single-family and three-family homes could make space for new, independent rental units. At five tables, designers worked together to carve out livable studio and one bedroom units in the basements, attics, and sides of existing sample floor plans. Three teams presented “carve out” units, and two teams presented basement units. Over the course of the charrette, many questions came up that forced designers to challenge their usual design processes in order to conform to the requirements of the pilot program. By the end of the evening, the five teams had demonstrated that a dedicated homeowner would have several options for fitting a new unit in their building, if they chose to take advantage of the pilot program.

All of the teams presented different variations on the “carve out” and basement unit types. One team separated out an existing office, kitchen, and bathroom at the front of a single-family home to form a new one bedroom ADU. Another split an existing unit front-to-back, creating two mirrored floor plans. A third split an existing unit side-to-side, creating two narrower one bedroom units without having to dramatically alter the existing floor plan. The basement unit floor plans were more straightforward, and could in many cases mirror the first or second floor layouts. Not all of these ideas would be viable for construction, though all were valuable test cases for the pilot program and sparked much discussion among the designers. Working from the ideas proposed in this charrette, the Housing iLab will continue to refine this policy and reduce the barriers presented to homeowners.

To learn more about the ADU pilot program, join the BSA Foundation on Tuesday, July 25 at 6:00 pm for a conversation with all of the Housing Innovation Lab Summer Fellows. Their work on ADUs, as well as other strategies for increasing housing affordability in the city, will be presented as part of a panel discussion.