Massachusetts ADU Laws 2026
Primary statutes: Mass. Gen. Laws ch. 40A § 3A (Affordable Homes Act, 2024)
Massachusetts passed historic statewide ADU legislation in 2024 as part of the Affordable Homes Act, allowing ADUs by-right on single-family lots in most municipalities.
At a glance
Full summary
The Affordable Homes Act of 2024 requires Massachusetts cities and towns to allow ADUs by-right on single-family residential lots. Owner-occupancy requirements are prohibited. Maximum size is 900 sqft or half the gross floor area of the primary dwelling, whichever is smaller.
The law also created a $25,000 homeowner grant program to help offset construction costs for income-eligible owners. Local zoning amendments to comply with the new law were due in February 2025; some towns have lagged in implementation.