ADU Rules in South Portland, Maine

South Portland is a Cumberland County city of about 26,000 directly south of Portland, separated by the Fore River and Casco Bay. Maine's third-largest city, South Portland is home to large oil tank farms along Casco Bay, the Portland International Jetport (which the city borders), and significant commercial development. Despite being adjacent to Portland, South Portland is an entirely separate city with its own government and Land Use Code. Maine has no statewide ADU preemption law — South Portland's local code governs.

South Portland vs. Portland

• South Portland: South side of the Fore River/Casco Bay — use South Portland's permit process
• Portland: Separate city to the north — different Land Use Code, different permits
• The two cities are connected by the Casco Bay Bridge and other crossings but have completely separate governments

South Portland Land Use Code

The City of South Portland Land Use Code governs all land use within South Portland city limits.

Permitted ADU Types

Depending on the zoning district:

• Accessory apartments: Within or attached to primary structure
• Detached accessory dwelling units: In eligible residential zones

Verify current ADU provisions with South Portland's Planning Division.

Size Limits

Accessory dwelling units are subject to:

• Maximum floor area per zone
• Lot coverage restrictions

Setbacks

Per South Portland residential zone (typical):

• Rear: Minimum setback
• Side: Minimum setback

Maine Shoreland Zoning

Properties within 250 feet of Casco Bay (tidal), the Fore River, Stroudwater River, or other water bodies are subject to Maine's Shoreland Zoning Act (Title 38). South Portland has extensive coastline on Casco Bay — verify shoreland zoning for any coastal or waterfront property.

Tidal and Coastal Areas

South Portland fronts Casco Bay with tidal areas, wetlands, and marinas. Properties near tidal waters have additional restrictions under Maine's shoreland laws.

Coastal Flood Zones

Properties near Casco Bay and waterways in South Portland may be in FEMA coastal flood zones. Verify flood map status.

Portland Jetport Proximity

Portland International Jetport is located in South Portland. Properties near the airport may be in FAA airspace or noise overlay zones. Verify if your property is in an airport overlay zone.

Permit Process

1. Verify jurisdiction: Confirm your property is in South Portland (not Portland)
2. Verify zoning: South Portland Planning Division
3. Check shoreland zoning: If near Casco Bay or waterways
4. Check airport overlay: If near Portland Jetport
5. Check flood zone status: If near coastal areas
6. Submit plans: South Portland Building Division
7. Building permit and inspections
8. CO: Required before occupancy

Contact

City of South Portland Planning Division 25 Cottage Road, South Portland, ME 04106 Phone: (207) 767-7605 Website: southportland.org

Disclaimer: Maine has no statewide ADU law. South Portland and Portland are separate cities. Maine Shoreland Zoning applies near Casco Bay. Verify current ADU allowances with the City of South Portland before starting any project.