ADU Laws in Maine (2026)
Maine state ADU law details, key provisions, preemption status, and recent legislative changes for accessory dwelling units.
Law Name
Maine LD 2003 — An Act To Implement Certain Recommendations of the Commission To Increase Housing Opportunities in Maine by Studying Zoning and Land Use Restrictions
Effective Date
2022-07-01
Preempts Local Ordinances
Yes — state law overrides local restrictions
Has State Law
Yes
Key Provisions
Requires municipalities with 2,000+ residents to allow at least one ADU on any owner-occupied single-family lot · Source
ADUs must be permitted as of right — no discretionary approval or public hearing required · Source
Municipalities may establish reasonable dimensional and design standards but may not effectively prohibit ADUs · Source
ADUs may be attached, detached, or created through conversion of existing space · Source
Municipalities may require owner-occupancy of either the primary or accessory dwelling · Source
ADUs must meet applicable building code and health and safety standards · Source
Municipalities with populations under 2,000 are not subject to the state mandate but may voluntarily permit ADUs · Source
Statewide building code standards apply to all new ADU construction · Source
Legislative History
Official Sources
What Does Preemption Mean for Local Cities?
Because Maine law preempts local ordinances, individual cities cannot impose restrictions stricter than the state standard. A city may still have additional administrative requirements, but cannot deny ADU applications that comply with state minimums.
Learn about Mainezoning preemption →Source: Maine LD 2003 — An Act To Implement Certain Recommendations of the Commission To Increase Housing Opportunities in Maine by Studying Zoning and Land Use Restrictions. Last verified April 5, 2026. View source