Massachusetts ADU Law: What You Can Build By Right
Published on: 05/08/2026
Massachusetts allows one ADU by right on most single-family lots. Here is what the law permits.
Additions & ADUs
Straight answers on what projects cost, what permits you need, and what Massachusetts law allows. Written by Andrew Mercurio, a fourth-generation builder working in Worcester County. Most homeowners start a project with the same handful of questions and get vague answers to all of them. These guides give you the real ones. What an addition actually costs in Central Massachusetts, what changed when the state legalized accessory dwelling units, when you need a permit and when you do not, and what to check on your property before you get attached to a plan. If you have a question these do not cover, call us at (774) 249-0221.

Massachusetts allows one ADU by right on most single-family lots. Here is what the law permits.