Massachusetts ADU FAQ
Common questions about the new Massachusetts ADU law and permit requirements
What is the new Massachusetts ADU law?
The 2024 Massachusetts ADU law requires all 351 cities and towns to allow at least one Accessory Dwelling Unit (ADU) by right on single-family residential properties. This means you no longer need special permits or public hearings in most cases.
How big can my ADU be in Massachusetts?
Under the new state law, ADUs can be up to 900 square feet or 50% of the floor area of the principal dwelling, whichever is greater. Some towns may allow larger ADUs.
Do I need a special permit for an ADU in Massachusetts?
No special permit is required for 'protected use' ADUs under 900 sq ft that meet state requirements. However, each town may have specific building permit requirements and fees.
What are ADU setback requirements in Massachusetts?
Setback requirements vary by town but cannot be more restrictive than what's required for the main house or other accessory structures in your zoning district. Use our town search tool to find specific setbacks for your municipality.
How much does it cost to get an ADU permit in Massachusetts?
Permit fees vary significantly by town, ranging from $100 to $2,000+. Our database includes fee information for all 351 Massachusetts municipalities.
Can I rent out my ADU in Massachusetts?
Yes, you can rent your ADU. There's no owner-occupancy requirement under the state law, though some towns may have additional restrictions.
What towns are covered by the Massachusetts ADU law?
The law applies to 350 out of 351 Massachusetts municipalities. Only the town of Nahant is exempt due to its unique geographic constraints.
How long does it take to get an ADU permit approved?
Timeline varies by town. Most building departments process ADU permits within 30-90 days. Our database includes estimated timelines for each municipality.
Can I build an attached or detached ADU?
Both attached and detached ADUs are allowed under state law. The choice may depend on your property layout and local zoning requirements.
What utilities are required for an ADU?
ADUs must have basic utilities including water, sewer, and electricity. Requirements cannot be more restrictive than state building codes or what's required for the principal dwelling.
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