Massachusetts Statewide Rule

Massachusetts Statewide ADU Zoning Reform Law

Few RestrictionsApplies statewide across Massachusetts (2026)

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.

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

Source: Massachusetts General Court

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?

No. Under the amended Chapter 40A Section 3, ADUs up to 900 square feet must be allowed by-right in single-family zones. Special permit requirements are preempted statewide.

Does the Massachusetts ADU law allow short-term rentals?

The state law allows municipalities to prohibit short-term rental use of protected ADUs. Many local bylaws restrict ADU use to long-term tenancies of 30 days or more.

Sources

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Full Breakdown

Frequently Asked Questions

Can a Massachusetts town still require a special permit for ADUs?

No. Under the amended Chapter 40A Section 3, ADUs up to 900 square feet must be allowed by-right in single-family zones. Special permit requirements are preempted statewide.

Does the Massachusetts ADU law allow short-term rentals?

The state law allows municipalities to prohibit short-term rental use of protected ADUs. Many local bylaws restrict ADU use to long-term tenancies of 30 days or more.