Portland, Maine

Portland, ME Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 10/10

Last Updated: 7.1.2024

Image source: Town of Cape Elizabeth

What You Need To Know

ADUs are permitted in Portland on all legal lots, and on qualifying lots, you can build up to two ADUs.

Type of ADU Permit Required

ADUs are permitted by right through the building department.

ADU Rules

  • Up to two ADUs are permitted per qualifying lot.

  • At the time of construction or creation, the owner of the property must live in at least one dwelling unit.

  • When an ADU is visible from public streets it must be clearly subordinate to the principal structure, and there may not be any exterior fire escapes above the ground.

  • If an ADU is created by converting a nonconforming structure, the privacy of the adjacent properties must be taken into consideration. 

  • ADUs are required to meet all dimensional requirements except for lot coverage and lot area per dwelling requirements.

  • ADUs are limited to 2/3s of the gross floor area of the principal dwelling(s).  

    • The height of the ADU cannot exceed the height of the primary structure.

Resources:

City of Portland Land Use Code- Article 6/Page 31

https://content.civicplus.com/api/assets/a5dcd1dc-4117-40b3-b3da-74a56919e14b

Attached ADU, Convert Existing Space, Detached ADUChris LeeFriendliness Score: 10/10, Portland, Maine, Greater Portland