Maine state law: ADU permitting under 30-A MRS § 4364-A and MUBEC (25 MRS § 2451)

Maine does NOT issue ADU permits at the state level. Permitting authority rests with the local municipal code-enforcement officer (CEO) under the building-code authority granted by 25 MRS § 2451 (Maine Uniform Building and Energy Code). MUBEC is adopted statewide and is mandatory in municipalities of 4,000 or more population; smaller municipalities may opt in. MUBEC incorporates by reference the International Residential Code (IRC), International Building Code (IBC), International Energy Conservation Code (IECC), National Electrical Code (NEC), and Maine state amendments. Plumbing inspection is performed by the state-licensed Local Plumbing Inspector under 22 MRS § 2491 et seq. While the local permit process governs construction standards (framing, egress, ceiling height, energy, electrical, plumbing, mechanical), the statewide ADU mandate at 30-A MRS § 4364-A constrains what conditions a municipality may attach: no owner-occupancy requirement; no more than one off-street parking space per ADU; no minimum-lot-size, minimum-floor-area, setback, or design standards more restrictive than those for the primary single-family dwelling. ADU proposals within the mandatory Shoreland Zone (38 MRS § 435 et seq.) require Shoreland review by the local Shoreland CEO and must comply with the 75-foot setback, vegetated-buffer, and impervious-surface limits of the DEP Shoreland Zoning Standards (06-096 CMR Chapter 1000). ADUs in mapped Special Flood Hazard Areas trigger floodplain-permit review under the local floodplain management ordinance adopted to maintain National Flood Insurance Program eligibility.

Constructing or occupying an ADU without required permits is a building-code violation enforceable by the local CEO under 30-A MRS § 4452, with civil penalties typically $100-$2,500 per day plus stop-work orders and injunctive relief in District Court.