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Accessory Dwelling Units (ADU)

What is an ADU?

An Accessory Dwelling Unit (ADU) is a self-contained dwelling unit that can be occupied independently from the principal structure, typically a single-family home. The unit must include complete housekeeping facilities, meaning a kitchen and bathroom as well as the living and sleeping area. 

ADUs can be located within or attached to the principal structure, or detached as a separate structure.

Where are ADUs allowed?

ADUs are permitted anywhere residential uses are allowed. ADUs must adhere to the development and design standards required by the Town Zoning Ordinance.

Use the interactive Zoning Map to check what Zoning District your property is located in. Once you have verified your Zoning District, review that District’s requirements for setbacks and the following standards for ADUs.  

Be sure to check your property’s deed restrictions and/or subdivision plan for any additional restrictions.

Development Standards

  • No more than two occupants are permitted to reside in an ADU.
  • The minimum size is 190 square feet. The maximum size depends on the size of the principal structure as follows:

If the living space of the principal structure is:

The living space of the ADU shall not exceed:

Under 2,000 sq. ft.

40% or 750 sq. ft.

2,000 sq. ft. or more, but less than 3,000 sq. ft.

35% or 750 sq. ft.

3,000 sq. ft. or more, but less than 5,000 sq. ft.

30% or 1,050 sq. ft.

Over 5,000 sq. ft.

20% or 1,500 sq. ft.
 
  • Proper ingress and egress must be provided to the ADU. See Section IX.J(11) for more information on external stairways.
  • An external/detached ADU must be located within 100 feet from the nearest point of the principal structure.
  • Internal/attached ADUs must meet the dimensional and setback requirements of the principal structure.
  • ADUs permitted in an existing accessory building or secondary building/garage must adhere to the setback requirements as of July 1, 2023.
     

Required Permits

ADUs require a building permit. Use the online fillable application forms or access at Town Hall in the Planning & Codes Department.

If a variance is required to allow for the construction of an ADU, an applicant for an ADU permit may also apply to the Zoning Board of Appeals for a Limited Reduction in Yard Size.

Exemptions for ADUs

ADUs are exempt from density requirements or lot area requirements of the Zoning District in which they are constructed, as well as rate of growth permit requirements.

Design Standards

Attached/internal ADUs shall retain and respect the character and architectural style of the principal structure. Detached ADUs must be designed in the style of a garage, barn, storage building, carriage house, accessory cottage, or similar structure.

Utility Connections

The ADU and principal structure must be serviced by common utility meters. For water and wastewater, the owner of the ADU must provide written verification that the ADU is connected to adequate services.

FAQs

Benefits of an ADU

ADUs can provide a range of benefits, including generating rental income, providing flexible options for intergenerational living, increasing property values, and adding needed units to the housing market.

Before getting started, it’s always a good idea to reach out to the Planning & Codes Department first to discuss your project. 

Contact

For questions about ADUs and the application process, contact the Planning & Codes Department at planning@scarboroughmaine.org or (207)-730-4040.