Under Land Use Code §6.6.2, the owner of a Portland lot must occupy at least one of the dwelling units at the time an ADU is initially constructed or legally created, with a Peaks Island legally-nonconforming-lot exception.
Portland's Land Use Code §6.6.2 requires that, at the time of an ADU's initial construction or legal creation, the owner(s) of the property must occupy at least one of the dwelling units on the lot. The principal unit and the ADU need not share an interior; the owner may live in either unit. A narrow exception applies to legally nonconforming lots on Peaks Island. The ordinance additionally requires the developer to record a deed restriction at the Cumberland County Registry of Deeds providing that the ADU and at least one other non-accessory unit on the site remain under common ownership — this prevents the ADU from being subdivided off and sold as a separate property. Importantly, the state statute at 30-A MRS §4364-B was amended in 2025 to prohibit municipalities from requiring continuing owner-occupancy after creation: subsection 2-B permits ADU construction 'even if the owner of the lot where the accessory dwelling unit is located does not reside in a dwelling unit on that lot.' Portland's ordinance accordingly applies the owner-occupancy requirement only at the moment of initial creation, not as a continuing condition of the ADU's use. Once the ADU is built and a Certificate of Occupancy issued, the owner may move out and rent both units to non-owner tenants, provided the common-ownership deed restriction is honored.
Building an ADU on a lot where the applicant is not an owner-occupier (outside the Peaks Island exception) is grounds for denial of the building permit by Portland Permitting and Inspections. Failure to record the required common-ownership deed restriction blocks issuance of the Certificate of Occupancy. Attempting to subdivide and sell the ADU separately from the principal unit in violation of the deed restriction creates a private cause of action under Maine deed-restriction law (Title 33 MRS) and a zoning violation enforceable under 30-A MRS §4452 with civil penalties up to $2,500 per day.
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