Portland, ME Accessory Structures: ADU Rental Restrictions (2026)

Portland's short-term rental ordinance (Chapter 6 of the Code of Ordinances, administered by Permitting and Inspections) caps the number of non-owner-occupied STR registrations citywide and runs a waitlist for new registrations once the cap is reached. To incentivize ADU production after LD 2003 (30-A MRS §4364-B) took effect, the Council amended the STR ordinance to exempt newly constructed ADUs from the non-owner-occupied cap for the first five years after creation. During that window, a Portland homeowner may register a new ADU as a short-term rental (less than 30 days per stay) and rent it through Airbnb, Vrbo, or another platform without competing for a waitlist slot, allowing the owner to recoup construction costs. After the 5-year window expires, the ADU must compete with all other applicants on the STR waitlist if the citywide cap remains exceeded. All STR registrations are subject to Maine's 9% lodging tax under 36 MRS §1811, collected by the platform under the marketplace facilitator rule at 36 MRS §1754-B. Owner-occupied STRs (where the host lives in the principal dwelling on the lot) are subject to a different, less restrictive registration tier under Chapter 6. The state ADU statute at 30-A MRS §4364-B does not directly regulate short-term rental use, so Portland's local STR rules apply.