Fourteen terms you will meet at the counter, in the bylaw, and at the kitchen table, in plain English.
A self-contained housing unit with its own sleeping, cooking, and sanitary facilities on the same lot as a principal dwelling, with a separate entrance. The Massachusetts statutory definition caps by-right size at half the principal dwelling’s gross floor area or 900 square feet, whichever is smaller.
Allowed under zoning without requiring a discretionary special permit or variance. By right does not mean no permits: building permits and applicable reviews still apply.
The main residence on the lot that the ADU accompanies.
The measure of building floor area used in the size limit. How it is calculated can vary; ask how your municipality measures it.
A term some communities use for a smaller unit created within the existing footprint of the home. Definitions vary by community.
The minimum required distance between a structure and a property line. Setbacks vary by district and municipality.
The portion of a lot that structures may cover, usually expressed as a percentage. Limits vary locally.
A discretionary municipal approval some projects require. A by-right ADU under the state framework should not require one, but confirm how your municipality applies the rules.
The Massachusetts State Environmental Code governing septic systems. On unsewered lots, septic capacity is often the first feasibility question.
The municipal sign-off, after inspections, that a unit may lawfully be occupied.
Rental for brief periods. Municipalities may regulate short-term rental of ADUs even where the ADU itself is by right.
A rule requiring the owner to live on the property. The state framework limits owner-occupancy conditions for by-right ADUs; verify how your municipality applies them.
The state regulation implementing the ADU provisions of the 2024 law, administered by the Executive Office of Housing and Livable Communities.
Municipal review under wetlands and related environmental rules where a lot contains or borders protected resources.
Educational information only. This resource provides general education and is not legal, tax, appraisal, engineering, lending, zoning, or construction advice. Verify all requirements with the applicable municipality and qualified professionals.