What is an accessory dwelling unit?

An accessory dwelling unit (ADU) is a self-contained residential unit that meets the requirements of the Minnesota State Building Code. ADUs are permanent homes that are legally part of a larger property that includes a standard single-family house. ADUs can be part of the principal building or they can be in a detached accessory building on the same property.

What is not considered an ADU?

  • A bedroom or living space that does not have its own kitchen (with large appliances) or bathroom.
  • A dwelling unit or mother-in-law suite that has full access to the living space in the main part of the house. If the dwelling unit doesn’t have its own lockable door, it’s not considered an ADU.
  • A second kitchen in the principal building that does not have an associated living space and full bathroom.

Use this checklist to determine if an ADU would be allowed on your property. City staff recommend answering “yes” to all relevant questions before applying for permits to construct an ADU.
  1. Do I own and live on the property where I would like to construct an ADU?
  2. Will my ADU include a kitchen with appliances, and a full bathroom, and be completely separate from the main house?
  3. If I want to construct an attached/interior ADU, will the ADU meet the following requirements:
    1. The ADU can be no more than 40% of the gross floor area of the principal building.
    2. Will the ADU be completely separate from the rest of the house (meaning a separate and lockable entrance)? Will the ADU share and have access to the living space in the main part of the house, and vice versa?
    3. Can I meet building code requirements, particularly fire separation requirements?
  4. If I want to construct a new detached ADU, will the ADU meet the following requirements:
    1. The ADU must be five feet from side interior lot lines.
    2. The ADU must be 15 feet from rear lot lines, unless the lot abuts an alley, then the ADU must be at least five feet from the lot line.
    3. The ADU must have a permanent foundation on footings.
    4. The ADU building must be no more than 15 feet tall, with a few exceptions.
    5. The ADU must be at least 200 square feet.
  5. A garage conversion to an ADU cannot happen unless the required parking for the single-family home can be located in a structure or behind the front face of the house. An ADU does not require additional off-street parking.

What is the city approval process to construct an ADU?

  1. Consult with staff on zoning and building code requirements. ADUs must meet the same requirements as any other apartment unit:
    1. Fire separation for attached ADUs: Floor, ceiling, fire wall between side-by-side units (like any other apartment unit).
    2. Egress & separate entrance.
    3. Water & sewer connections – whether separate from main house or not, lines must be sized to adequately serve the demand from all features and units.
    4. Tenant must be able to control their own utilities: hear/air, breakers (same as any apartment building), water shut-off, etc. The ADU does not necessarily need separate billing.
    5. All ADUs should follow the new residential construction handout.
    6. Converting existing garages: frost footings, slab/foundations for 2 stories, etc.
  2. Apply for permits:
    1. If demolition is part of the project, you will need a demolition permit.
    2. All ADUs will require a building permit, and may require electrical, mechanical, and/or plumbing permits.
    3. An erosion control permit is required if the project will disturb 5,000 cubic feet. See this handout for more details.
    4. Additions to the main house that add a second story or add five hundred square feet (500) or greater will require a construction management plan.
  3. Once all permits are finalized, a certificate of occupancy will be issued for detached ADUs.
  4. Apply for a rental license if the ADU will be rented out.

Background

In January 2019, the city council decided to discuss accessory dwelling units (ADUs). An ADU is a self-contained residential unit that meets the requirements of the Minnesota State Building Code. ADUs are permanent installations that are legally part of a larger property that includes a standard single-family house. ADUs can sometimes be referred to as: carriage or coach houses, accessory apartments, backyard cottages, secondary dwelling units, granny flats, mother-in-law suites, second suites or garden apartments. These units may be located inside the principal building on a lot, or may be located in a detached accessory building on the same parcel.

ADUs have the potential to meet some of St. Louis Park’s housing and land use goals in the 2040 Comprehensive Plan update. Permitting ADUs in the city also helps fulfill the following city council strategic priority: St. Louis Park is committed to providing a broad range of housing and neighborhood-oriented development.

Resources and documents