Accessory Structures in Portland, ME (2026)
2 verified accessory structures rules for Portland, Maine, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Portland's Land Use Code lets homeowners build up to two accessory dwelling units per qualifying property, by right, on any lawfully conforming or nonconforming lot with an existing legal residential use. A detached ADU tops out at 18 feet, 25 feet if built over a garage, and its floor area can't exceed two-thirds of the largest principal unit's gross floor area, effective under the Land Use Code that took effect July 1, 2026.
Portland ADU Size, Height & Permit Rules
Some RestrictionsPortland Code of Ordinances § 6.6.2(A) (Land Use Code, eff. 7/1/2026)
1. Accessory Dwelling Units (ADUs) shall be permitted on all lawfully conforming and nonconforming lots with legal residential uses. ... 3. Up to two ADUs shall be permitted per qualifying property. ... 5. An ADU shall be limited to a gross floor area of 2/3 of the gross floor area of the largest principal unit on the lot. The aggregate square footage of detached ADUs on a lot shall not exceed ...
Shed & Carport Rules
A small shed or detached accessory structure of 250 square feet or less can sit as close as 5 feet to the rear lot line in Portland's RN-1 through RN-4 zones (3 feet in RN-6), with interior side setbacks as tight as 3 feet in RN-3/RN-4, and its height is capped at 18 feet under Land Use Code Table 7-A.
Portland ME Shed and Accessory Structure Rules
Some RestrictionsPortland Code of Ordinances, Land Use Code, Article 7 § 7.3, Table 7-A (eff. 7/1/2026)
TABLE 7-A: RESIDENTIAL NEIGHBORHOOD ZONE DIMENSIONAL STANDARDS. Rear setback (min.), Detached accessory structures (≤250 SF footprint): RN-1 5 ft.; RN-2 5 ft.; RN-3 5 ft.; RN-6 3 ft. Side setback, interior (min.), Detached accessory structures (≤250 SF footprint): RN-1 5 ft.; RN-2 5 ft.; RN-3 3 ft.; RN-4 3 ft. Detached accessory structure height (max.): RN-1 18 ft.; RN-2 18 ft.; RN-3 18 ft.