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ADU Town Regulations

Portland, ME

Apr 24, 2024

Last Updated

About

Portland, Maine, is an energetic coastal city known for its rich history, scenic beauty, and thriving cultural scene. Located on the southern coast of Maine, Portland offers a perfect blend of urban sophistication and New England charm, with its bustling Old Port district, renowned restaurants, art galleries, and picturesque waterfront. Portland is the most populous city in the U.S. state of Maine and the seat of Cumberland County. Portland's population was 68,408 in April 2020. The Greater Portland metropolitan area has a population of approximately 550,000 people. Historically tied to commercial shipping, the marine economy, and light industry, Portland's economy in the 21st century relies mostly on the service sector.

ADU Rules

  • Accessory Dwelling Units (ADUs) shall be permitted on all lawfully conforming and nonconforming lots with legal residential uses. ADUs shall comply with all dimensional standards of the underlying zone unless otherwise provided below:

  • Up to two ADUs shall be permitted per qualifying property.

  • An ADU shall be limited to a gross floor area of 2/3 of the gross floor area of the principal unit(s). In no circumstance shall the height of detached ADUs on a lot exceed the height of the primary structure. Additionally, the aggregate square footage of detached ADUs on a lot shall not exceed the gross floor area of the primary structure

  • At the time of an ADU’s initial construction or legal creation, the owner(s) of the property on which the accessory dwelling unit is created must occupy at least one of the dwelling units, with the exception of legally nonconforming lots on Peaks Island.

  • When an ADU is significantly visible from public ways, the building design shall:

    • Be clearly subordinate to the principal structure(s) in scale and position in relationship with the street and principal structure(s).

    • Not include outside stairways or fire escapes above the ground floor.

  • Under circumstances where an existing nonconforming structure is converted to an ADU, the design of the ADU shall take into consideration to the extent practicable the privacy of adjacent properties.

  • The developer of an ADU shall record a deed restriction requiring that the ADU and at least one other non-accessory unit on-site remain under common ownership.

  • ADUs shall comply with all dimensional requirements of the underlying zone except lot coverage and lot area per dwelling unit requirements.

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