The Boston Foundation: The 2024 Affordable Homes Act legalized accessory dwelling units (ADUs) across Massachusetts (except in Boston), taking effect February 2025. In the first year, municipalities received more than 1,600 permit applications and issued more than 1,200 permits—a clear increase over prior years, but still short of meeting the state’s target pace.
Our research finds that sustained ADU construction will require follow-up work on multiple fronts, including:
- The Commonwealth should set clear dimensional requirements for ADUs, such as minimum setbacks and maximum height, and allow municipalities to be more permissive with zoning requirements, but not more restrictive.
- State regulatory standards for ADUs should be reviewed and revised to support ADU production while protecting health, safety, and the environment.
- Permit review processes should be regionalized.
- Cross-departmental coordination at the local and state levels should be increased.
The report also discusses lessons from this early experience with ADU legalization that can help guide future housing reform efforts:
- Direct state-level legalization of housing production unlocks more new housing than one-off municipal efforts. State-level zoning reform accomplished more in one year than 50 years of local reform did.
- Zoning reform alone is insufficient. We need a comprehensive agenda to address other regulatory barriers spanning building, fire, energy, septic system, wetlands, and stormwater rules.
For much more, including recommendations for specific regulatory tweaks, read the full report: ADUs Turn One: Regulatory Barriers to production in Massachusetts and Ideas for Further Reform | Boston Indicators
