Maine LD 2003 / 30-A M.R.S. §4364 — Statewide ADU Mandate (ME)
Tracked preemption from the Maine overlay bundle.
Overview
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Effective
2023-07-01
Sunset
—
Authority
state
Scope
state:ME
Other Maine preemptions
Maine Short-Term Rental Framework — 30-A M.R.S. §4364 (2024 Amendments)Maine LD 2003 / 30-A M.R.S. §4364-A — 2-4 Unit Middle Housing FloorMaine LD 2003 / 30-A M.R.S. §4358 — Affordable Housing 2.5x Density BonusMaine 30-A M.R.S. §4358(2) — Manufactured Housing ProtectionMaine Growth Management Act — Comprehensive Plan Consistency RequirementMaine 30-A M.R.S. §4326 — Growth / Rural / Transition Area Tripartite DesignationMaine Mandatory Shoreland Zoning Act — 38 M.R.S. §§435-449Maine Land Use Planning Commission — Unorganized Territory Zoning Authority
Primary-source summary
**Last reviewed**: April 2026
**Activity level**: High — LD 2003 (Public Law 2021 Ch. 672, effective July 1, 2023) imposed a statewide ADU mandate, 2-4 unit duplex-by-right in designated growth areas, and affordable-housing density bonuses. Maine has continued to amend the Growth Management Act and short-term-rental authority in the 131st and 132nd Legislatures (2023-2026). The Land Use Planning Commission (LUPC) remains the zoning authority of record across Maine's vast unorganized territory.Trigger predicate
When this evaluates true for a parcel, the law's preempted fields take precedence over base zoning.
AND
city.has_zoning_ordinance==Truecity.in_unorganized_territory==Falseparcel.base_zone_category∈ {res_sf,res_mf,res_th,mu}
Preempted fields
7 fields on the base district schema are rewritten when the trigger fires.
| Field | Op | Value | Note |
|---|---|---|---|
base_districts[category=res_sf].allowed_uses | add | adu | At least one ADU per lot where SF dwelling is permitted or legally existing; internal, attached, or detached |
base_districts[category=res_sf].owner_occupancy_required_adu | waive | — | §4364 prohibits local owner-occupancy requirements |
base_districts[category=res_sf].family_relationship_restriction_adu | waive | — | |
base_districts[category=res_sf].min_lot_area_increase_for_adu | waive | — | Municipality may not require minimum lot size beyond the base lot |
base_districts[category=res_sf].parking_ratio_adu | cap_at | 1.0 | Max 1 off-street space per ADU |
base_districts[category=res_sf].parking_ratio_adu | waive | — | No parking requirement within 1/2 mile of transit |
review_type | waive_discretionary | — | Subdivision review does not apply to ADU creation |
Citation
Authority source
30-A M.R.S. §4364; Public Law 2021 Chapter 672 (LD 2003)
§ §4364 (Accessory dwelling units)
Research notes
Self-executing preemption — inconsistent municipal ordinances unenforceable to extent of conflict. Aggrieved applicants may seek Rule 80B review in Superior Court. Implementing guidance now sits at Maine Office of Community Affairs (MOCA) post-2024 reorganization (previously DECD Office of the State Planner). Federal conflict check enabled for Acadia NP boundary parcels and Indian Settlement Act lands where federal/tribal land use rules may control. LD 2173 (pending, March 2026) would push effective date to July 1, 2027.