Cumberland County, ME Accessory Structures: ADU Rental Restrictions (2026)

There is no county ordinance restricting how an ADU may be rented in Cumberland County. The statewide ADU mandate at 30-A MRS § 4364-B treats the ADU as a residential dwelling unit, and 30-A MRS § 3001 home-rule analysis under LD 2003 means a municipal ordinance cannot prohibit long-term residential rental of an ADU — a flat ban would 'frustrate the purpose' of the LD 2003 mandate to expand housing supply. However, LD 2003 does NOT preempt short-term rental regulation. Several Cumberland County municipalities (most prominently Portland under its Land Use Code Article 6 STR ordinance) impose registration, occupancy caps, owner-occupancy requirements, or outright prohibitions on ADUs used as STRs (under 30 days). Statewide, every STR (including an ADU rented short-term) is subject to the 9% lodging sales tax under 36 MRS § 1811, collected by the platform under 36 MRS § 1754-B if booked through Airbnb/Vrbo/Booking.com once the marketplace facilitator's Maine sales exceed $100,000 in a calendar year. Tenancies in ADUs are governed by Title 14 landlord-tenant law (14 MRS § 6000 et seq. for FED, § 6021-A implied warranty of habitability, § 6028 security-deposit rules).