Research from JCHS at Harvard Compares ADU Issues in Massachusetts to Other States

Nov 21, 2023

New research by the Joint Center for Housing Studies at Harvard University (JCHS) examines policies and initiatives to promote the creation of accessory dwelling units (ADUs), which have been advanced as a housing solution for age-friendly communities.

ADUs are small, independent living units that are inside, attached to, or detached, but on the same property as a primary residence and have the potential to address a variety of housing-related challenges like affordability, equity, and environmental issues. As the JCHS research explains, because ADUs generally are small infill units, they can achieve these gains without significantly altering the character of existing residential neighborhoods.

The report, titled “ACCESSORY DWELLING UNITS: LESSONS FOR MASSACHUSETTS FROM AROUND THE COUNTRY,” holds up Portland, Oregon and several statewide approaches as examples to follow, but Massachusetts now has the Affordable Home Act to consider, which is a $4 billion plan that includes statewide ADUs by-right.

Three key insights emerge from the JCHS research:

  1. Efforts to significantly increase the production of ADUs are most likely to succeed if they include state laws requiring by-right local approvals of ADUs that meet statewide standards for ADUs’ size, massing, design, and use.
  2. In establishing such requirements, policymakers must decide whether to pursue a more ambitious and politically controversial “comprehensive” approach that also limits localities’ ability to impose restrictions on occupancy and require extensive new on-site parking or a less controversial “incremental” approach that requires by-right approvals but is silent on occupancy and parking.
  3. Taking these steps will spur others to address the non-legal barriers that limit the construction of ADUs such as providing homeowner education programs and offering new ways to finance ADUs.

More information is available in the full report that may be informative to communities working to become more age- and dementia friendly as well as proponents of statewide ADU legislation.