03/24/2026
Many people ask me about ADU's (Accessory Dwelling Units). Here's MA info for anyone wanting to buy an eligible property or who wants to build an ADU on current property:
Effective February 2, 2025, Massachusetts’ Affordable Homes Act legalizes one "by-right" accessory dwelling unit (ADU) on single-family lots, removing the need for special permits. ADUs are restricted to 900 sq ft or 50% of the primary dwelling's size, whichever is smaller, and owner-occupancy cannot be required.
Definition & Size: ADUs are secondary units (attached, detached, or interior) limited to 900 sq ft or half the primary home's floor area.
Permitting: Allowed "by-right" (no special permit) on single-family lots, allowing faster approval.
Occupancy: Owners are not required to live on-site in the primary unit.
Parking: Municipalities are limited in the number of additional parking spaces they can require.
Restrictions: While municipalities cannot ban them, they can regulate them and restrict ADUs from being used as short-term rentals.
Purpose: The legislation aims to increase housing supply, allowing for more housing for families, elderly, or rentals.
These rules apply statewide, overriding most local restrictive zoning, and are designed to facilitate easier development of backyard cottages, basement apartments, or garage conversions.
I hope this helps! If you have questions, or are thinking of buying or selling a home, contact me!
Christine. [email protected]
Berkshire Hathaway Homeservices Commonwealth Real Estate
508-341-6454
Licensed in MA & RI