Maine ADU Rules Law: Statewide Accessory Structures Rules (2026)

Key Facts

Statute: 30-A MRSA 4364
Effective: July 1, 2023
Minimum allowance: 1 ADU per lot
Owner-occupancy: Cannot be required
Growth areas: Up to 4 units

Full Breakdown

Effective July 1, 2023, 30-A MRSA section 4364 requires Maine municipalities with zoning to permit one ADU per single-family residential lot, either attached, detached, or within the existing structure. Towns may not prohibit ADUs, require additional parking beyond what is required for the primary dwelling, mandate owner occupancy, or impose minimum lot size requirements that effectively block ADUs. Municipalities retain authority over reasonable dimensional standards, building code compliance, septic capacity, and shoreland zoning. Designated growth areas must allow up to four units per lot under the same statute.

Violations & Penalties

No criminal penalties. Property owners denied ADUs under non-compliant local rules may seek judicial review and damages under 30-A MRSA section 4482-A.

Frequently Asked Questions

Can my town require owner occupancy of the main house?

No. The 2023 statute specifically prohibits municipalities from requiring owner occupancy as a condition of ADU approval anywhere in Maine.

Does the ADU law apply in shoreland or rural towns without zoning?

It applies in all towns that have adopted zoning. Towns without zoning have no ADU restrictions to begin with. Shoreland zoning standards still apply on top.

Maine Statewide ADU Law Preempts Local Bans