An ADU (Accessory Dwelling Unit) is a self-contained living space located on the same property as your main home. Think of it as a complete, independent home—just smaller. To qualify as a "Protected Use ADU" under Massachusetts law, it must have:

• Its own kitchen (cooking facilities)
• Its own bathroom (sanitation facilities)
• Its own bedroom (sleeping area)
• A separate entrance (independent access)

It's essentially a fully functional home on your property—whether it's a converted basement, an addition to your house, or a detached cottage in your backyard.

In most cases, NO. This is the game-changer.

Under the Affordable Homes Act (signed August 2024, effective February 2025), ADUs are now allowed "by-right" in all single-family zoning districts across Massachusetts. This means:

No special permit required for standard ADU projects
No discretionary hearings before Zoning Boards
No neighbor approval needed
Municipalities cannot unreasonably prohibit ADUs

You still need:

• Building permit (standard process)
• Compliance with building codes
• Health department approval (septic, if applicable)

Bottom line: The state has removed the biggest barrier—arbitrary zoning restrictions.

Massachusetts law sets a clear maximum:

Your ADU cannot exceed the SMALLER of:
1. 900 square feet, OR
2. 50% of your main house's gross floor area (GFA)

Example:

• Main house: 2,400 sq ft → Max ADU: 900 sq ft (because 50% = 1,200, but 900 is the cap)
• Main house: 1,600 sq ft → Max ADU: 800 sq ft (because 50% = 800, which is under the 900 cap)

What counts as GFA?

• Finished basements (if ceiling height ≥7 feet)
• Main floors
• Finished attics/lofts

What doesn't count?
• Crawl spaces
• Unfinished attics
• Open porches
• Garages (unless converted into living space)

No. This is a major change under the new law.

Previous Rule (Pre-2025): Many towns required owner-occupancy.

New Rule (2025+): Towns are prohibited from requiring owner-occupancy of either the main house or the ADU.

What this means:
• You can live in the main house and rent the ADU
• You can live in the ADU and rent the main house
• You can rent BOTH if you move but keep the property
• Maximum investment flexibility

This makes ADUs attractive for:
• Investors
• People who may relocate for work
• Families planning future moves

Be careful here. The answer is: It depends on your town.

State Law: Allows municipalities to regulate short-term rentals.

Most Towns: Ban short-term rentals (typically defined as less than 30-31 days) for ADUs.

Examples:
• Lowell: Requires minimum 30-day rentals
• Natick: Similar short-term rental restrictions
• Boston area towns: Most prohibit short-term ADU rentals

Long-term rentals (30+ days) are protected and allowed statewide.

Why the restriction?
The state wants ADUs to provide stable, long-term housing—not hotel-style accommodations.

Our Advice: If you're planning to rent, plan for long-term tenants (6-12 month leases). This also provides more stable income.

Good news: Under the new law, neighbors cannot block your ADU.

Legal Reality:
• ADUs are "by-right" in MA (no special permit needed)
• No public hearing where neighbors can object
• Municipalities cannot require neighbor approval