ADU rules in Augusta

Augusta allows one accessory dwelling unit, detached or attached, on any parcel where a one- or two-family dwelling is the only residential use on the lot. The rule sits in the Land Use Ordinance at § 300-524E, added by Ord. No. 25-192 adopted 12-4-2025. The Table of Land Uses in the Base Zoning Districts (300 Attachment 4) lists 'Accessory Dwelling Unit' with an X, meaning a permitted use requiring a permit from the Code Enforcement Officer, in all 23 base districts that allow dwellings; the only district with no entry is Government Services (GS), which covers publicly owned institutional land. A detached ADU is built as an accessory structure and only has to meet the accessory-structure setback, five feet from side and rear lines in the RA, RB1 and RB2 residential districts. Density standards, lot size and on-site parking expressly do not apply to it.

The same section covers ADUs inside, attached to, or detached from the house. § 300-202 defines an ADU as 'a self-contained dwelling unit located within, attached to, or detached from a one-family dwelling located on the same parcel of land,' so a basement, upstairs or internal conversion qualifies, and § 300-524E(2)(c) sets the rule for a 'building addition ADU, attached to the principal structure,' which must meet the setbacks of the primary structure rather than the looser accessory-structure setbacks. Attached and internal ADUs get the same exemptions from density standards, lot size and on-site parking as detached ones, and the same permitted-use status in the land use table.

§ 300-524E(2) sets a floor and a proportional ceiling rather than a flat number: minimum floor area at least 190 square feet, matching the state minimum in 30-A M.R.S. § 4364-B(6), and maximum floor area not exceeding the floor area of the primary structure on the property. On a large house that is a generous cap; on a small cottage it is the binding constraint. 'Floor area' is defined in § 300-202 as the sum of the horizontal floor areas enclosed by exterior walls plus unenclosed porches and decks. There is no ADU-specific height limit and no ADU-specific lot coverage rule; a detached ADU takes the accessory-structure setback (five feet side and rear in RA, RB1 and RB2) and an attached one takes the principal-structure setback (ten feet side and rear in those districts).

Augusta imposes no owner-occupancy requirement. § 300-524E(2) is an exhaustive list of the standards that apply to an ADU (minimum and maximum floor area, setbacks, water and sewer, other applicable codes) and contains no residency condition, and a full-text search of the Augusta Code turns up no owner-occupancy language for dwellings. The state ADU statute has been silent on owner occupancy throughout the period Augusta has had to comply. Maine did enact an explicit ban at 30-A M.R.S. § 4364-B(4)(E) in PL 2025, c. 385, § 17, but PL 2025, c. 733, § 25 (approved 4-16-2026) struck c. 385's staged application clause and, retroactive to 9-24-2025, pushed that whole act to apply to municipalities beginning July 1, 2027. The ban is therefore future law; Augusta already satisfies it.

§ 300-524E(1) states that on-site parking standards 'SHALL NOT apply' to an ADU, and the parking schedule in § 300-513 (Table 300-513-B) lists 'Accessory dwelling unit (ADU): None required' under its Residential heading, in contrast to the one space per dwelling unit required for a dwelling generally. The primary house keeps its own requirement; the ADU simply adds nothing. This matches 30-A M.R.S. § 4364-B(4)(C), which has barred additional ADU parking requirements since Augusta's implementation date of January 1, 2024. § 300-513 was itself amended by the same 12-4-2025 ordinance (Ord. No. 25-192) that added § 300-524E.

An ADU is a by-right, administratively permitted use. The key to the Table of Land Uses reads 'X = Permitted Use (requires a permit from the Code Enforcement Officer)' and distinguishes CU (conditional use, Planning Board review and a public hearing), PB and SE; 'Accessory Dwelling Unit' carries a plain X in every base district except GS, with no footnote. In practice the applicant files the city's Residential Building Permit Application with the Bureau of Code Enforcement, which does the zoning, setback and CEO/local plumbing inspector sign-off. Two overlays can escalate this. Inside a locally designated historic district, § 300-316.5I(3) requires a historic preservation certificate from the Augusta Historic Preservation Commission for new construction of a principal or accessory structure visible from the street. Inside the Shoreland Overlay an ADU is reviewed as a 'structure accessory to allowed uses,' a Code Enforcement Officer permit in the Limited Residential, General Development and Limited Commercial Districts but a Planning Board permit in the Resource Protection and Stream Protection Districts.

Chapter 300 places no limit on renting an ADU: § 300-524E imposes no occupancy, tenure or family-relationship condition, and § 300-202 defines a dwelling unit to include 'rental units that contain cooking, sleeping, and toilet facilities regardless of the time period rented.' A full-text search of the Augusta Code returns zero hits for 'short-term rental,' and there is no rental registration or lodging license: Chapter 221 (Rental Property) covers only bedbug abatement, and the license list in Chapter 190 (bottle clubs, waste facilities, massage, tattooing, cannabis, liquor, taxis, homeless shelters) has no lodging or short-term rental category. Nightly renting can still trip a zoning use test if it grows into a business: a bed-and-breakfast/tourist home, defined as a place advertising itself as a bed-and-breakfast serving at least one meal a day, is a separate use needing conditional-use approval in the residential districts, and 'hotel' is defined as more than 16 rooms of transient lodging. The ordinance says nothing about selling an ADU separately from the house; carving off a lot would go through Part 4, Subdivision and Site Plan Review.