ADU rules in Lewiston

A detached backyard ADU is allowed by right. Appendix A, Article XII, Section 11 permits one ADU on any lot holding a single-family, two-family, or multi-family dwelling or a mobile home, and says the unit may be attached to or detached from the principal dwelling so long as it sits on the same parcel on a permanent foundation. Ordinance No. 26-05, effective March 5, 2026, widened this from single-family-detached lots only. The Article XI land use table replaced by Ordinance No. 26-10 on June 4, 2026 marks 'Accessory dwelling units in accordance with the standards of Article XII' as P, permitted, in all sixteen mapped districts from Rural-Agricultural through Mill, never as a conditional use. Siting rules are ministerial: a detached ADU goes to the side or rear of the principal dwelling with a front setback at least equal to the principal dwelling, unless the lot exceeds one acre and the house sits back at least twice the required front setback.

Attached and internal ADUs are allowed by right on the same terms as detached ones, since Section 11 lets the unit be 'attached to or detached from the principal dwelling'. An attached ADU meeting the Section 11 standards counts as part of the single-family dwelling and is not treated as a separate dwelling unit for Article XI space and bulk purposes, so no extra lot area or frontage is required and the unit does not count against the district's net lot area per dwelling unit. The one design condition that bites is entrances: an attached ADU and the principal dwelling may have only one main entrance on the front of the building, and any other entrance must be designed to look subordinate.

The habitable area of the ADU may not exceed 900 square feet and may not contain more than two bedrooms, with a floor of 190 square feet that matches Maine's statutory minimum. There is no percentage-of-primary-dwelling cap and no ADU-specific height limit, so the district's ordinary space and bulk standards in Article XI, Section 23 govern height and setbacks. No additional lot size or street frontage is required for the ADU, and it does not count toward the zoning district's net lot area per dwelling unit requirement, though structure setbacks still apply.

Article XII, Section 11(3) requires that either the ADU or the primary dwelling be owner-occupied, so the owner has to live on the property, though not necessarily in the main house. The city's ADU fact sheet spells out the consequence: the owner may not rent both dwellings. This requirement is lawful and enforceable today. Maine's ban on municipal owner-occupancy rules, 30-A M.R.S. section 4364-B(4)(E), was enacted by PL 2025, chapter 385, section 17, but that Act's application clause was rewritten by PL 2025, chapter 733, section 25 (LD 2173, approved April 16, 2026), which struck the July 1, 2026 branch outright and left the Act applying to all municipalities beginning July 1, 2027; section 26 of the same Act makes that change retroactive to September 24, 2025, so no 2026 window ever took effect. Expect this field to flip to no on July 1, 2027 unless Lewiston repeals Section 11(3) sooner.

Article XII, Section 11(6) states flatly that no additional parking is required for the ADU, which matches the state floor in 30-A M.R.S. section 4364-B(4)(C) barring parking requirements beyond those for the single-family dwelling on the lot. The real access constraint is the driveway rule rather than a space count: the ADU must share the same driveway opening that serves the principal dwelling, no new curb cuts or driveways may be created for the ADU, and any new or expanded driveway entrance curb cut on the property is capped at twenty-four feet wide.

An ADU is a permitted use reviewed administratively, not a conditional use. The Article XI land use table shows P rather than C for ADUs in every district where they are listed, and Article V, Section 5(a)(1) requires only a permit from the code enforcement official for construction or alteration of a structure, with a certificate of occupancy under Section 7 at the end. The city's own guidance says new ADUs 'may be constructed with a building permit'. Planning board development review does not attach, because Article XIII, Section 2(b) exempts single-family and two-family construction and Section 2(a)(5) triggers review only when a modification nets three or more dwelling units. One extra step comes before occupancy: Section 11(7) requires evidence recorded in the Androscoggin Registry of Deeds that the ADU conforms to Article XII, Section 11, and the city publishes a recordation form for it.

Renting the ADU long term is allowed, but not renting out the whole property: Section 11(3) requires the owner to occupy either the ADU or the principal dwelling, and the city's fact sheet states that the owner shall not be permitted to rent both dwellings. That constraint holds until Maine's owner-occupancy ban reaches all municipalities on July 1, 2027. The ownership rule is separate and has no sunset: the principal dwelling and the ADU must remain in common ownership, so the ADU cannot be sold off or condominiumized, and a deed record proving conformity must be filed with the Androscoggin Registry of Deeds and given to the city before the occupancy permit issues. Lewiston has no short-term rental ordinance: the zoning code contains no short-term or vacation rental use, and the Chapter 22, Article XVII lodging house licensing program (Ord. No. 23-21, 9-14-23) expressly excludes vacation rentals from the definition of lodging house. The city's rental registration program reaches only buildings with three or more dwelling units, so a house plus one ADU is outside it.