Massachusetts Statewide Rule
Massachusetts Statewide ADU Zoning Reform Law
Key Facts
- Statute
- MGL Chapter 40A Section 3
- Maximum Size
- 900 square feet
- Approval Type
- By-right, no special permit
- Owner Occupancy
- Cannot be required
Summary
The 2024 Affordable Homes Act amended MGL Chapter 40A to require all Massachusetts municipalities to allow accessory dwelling units by-right in single-family zoning districts, preempting restrictive local rules.
No zoning ordinance or by-law shall prohibit, unreasonably restrict or require a special permit or other discretionary zoning approval for the use of land or structures for a single accessory dwelling unit, or the rental thereof, in a single-family residential zoning district; provided, that the use of land or structures for such accessory dwelling unit under this paragraph may be subject to reasonable regulations, including, but not limited to, 310 CMR 15.000 et seq., if applicable, site plan review, regulations concerning dimensional setbacks and the bulk and height of structures and may be subject to restrictions and prohibitions on short-term rental, as defined in section 1 of chapter 64G. The use of land or structures for an accessory dwelling unit under this paragraph shall not require owner occupancy of either the accessory dwelling unit or the principal dwelling; provided, that not more than 1 additional parking space shall be required for an accessory dwelling unit; and provided further, that no additional parking space shall be required for an accessory dwelling located not more than 0.5 miles from a commuter rail station, subway station, ferry terminal or bus station.
Full Breakdown
Section 3 of MGL Chapter 40A, as amended by the Affordable Homes Act of 2024, requires that ADUs of up to 900 square feet be allowed by-right on any lot zoned for single-family residential use. Municipalities cannot impose owner-occupancy requirements, additional parking minimums beyond one space, or special permit requirements on these protected ADUs. Local zoning may still regulate dimensional setbacks, building code compliance, and short-term rental use. The law took effect in February 2025 and was implemented through Executive Office of Housing and Livable Communities (EOHLC) regulations at 760 CMR 71.
Violations & Penalties
Municipalities denying compliant ADU applications face Land Court reversal and potential housing appeals committee orders; property owners face standard zoning enforcement only for actual violations of permitted dimensions.
Frequently Asked Questions
Can a Massachusetts town still require a special permit for ADUs?
Does the Massachusetts ADU law allow short-term rentals?
Sources
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