As of February 2025, Massachusetts changed the rules. Under the Affordable Homes Act, accessory dwelling units under 900 square feet are allowed by right in single-family zoning districts across the state — meaning most homeowners no longer need a special permit or a trip to the zoning board.
No variance or special permit required for a qualifying ADU (≤900 sq ft or 50% of your home's size, whichever is smaller)
Local zoning rules that conflict with the state ADU law are no longer enforceable
You still need a standard building permit, septic/sewer sign-off, and a Certificate of Occupancy
A 2-minute eligibility checklist by lot type and town — including how Boston's Article 53 fits in.
What a realistic schedule looks like, permit to move-in.
Detached new-build, garage conversion, and attached/basement — with 2026 Massachusetts numbers.
What Massachusetts homeowners are actually using in 2026.
For designers and contractors alike — so you compare apples to apples.
We use your town only to check the rules that apply to your property. No spam, no sales calls.
