Zoning › State preemptions › Maine

Maine LD 2003 / 30-A M.R.S. §4364-A — 2-4 Unit Middle Housing Floor (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 — Statewide ADU MandateMaine 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 == True
  • city.in_unorganized_territory == False
  • city.state_approved_comp_plan == True
  • parcel.base_zone_category ∈ {res_sf, res_mf, res_th, mu}
  • parcel.served_by_public_water_sewer == True

Preempted fields

6 fields on the base district schema are rewritten when the trigger fires.

FieldOpValueNote
base_districts[category=res_sf].allowed_usesaddduplex2 dwelling units per lot allowed everywhere housing is a permitted use
base_districts[category=res_sf].max_units_per_lotfloor_at2
base_districts[category=res_sf].allowed_usesaddtriplexUp to 4 units per lot in designated growth areas
base_districts[category=res_sf].allowed_usesaddfourplex
base_districts[category=res_sf].max_units_per_lotfloor_at4
base_districts[category=res_sf].min_lot_area_sfwaive—Municipal minimum-lot-size rules may not defeat the density floor

Citation

Authority source
30-A M.R.S. §4364-A; Public Law 2021 Chapter 672 (LD 2003)
§ §4364-A (Multi-unit dwellings by right in designated growth areas)
https://legislature.maine.gov/legis/statutes/30-A/title30-Asec4364.html

Research notes

Density floor applies only on lots served by (or with capacity for) adequate water and wastewater. 4-unit tier requires the municipality to have a state-approved comprehensive plan with §4326 growth-area designations. Per the May 2026 dossier, LD 2173 (pending) would double the non-growth-area minimum-lot-size floor from 5,000 sf to 10,000 sf. Confirm growth-area shapefile per city. MOCA (post-2024) custodies the comp-plan registry.