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Permit- Accessory Structures, Detached Garages and Sheds

  • Departments:Inspection
  • Divisions:Resident Services & Programs, Permits- Residential
  • Phone:(414) 766-7000

Accessory Structures Brochure

Accessory Building Permit Application


Accessory uses are those that are typically associated with the principal use of the property, and are located on the same parcel as the primary structure.
Accessory structures are buildings such as garages and sheds that are not attached to the principal structure on the property.


When thinking about building an accessory structure, there are several steps to follow. This brochure outlines the necessary steps that need to be taken to be in compliance with the City of Oak Creek Municipal Code.


  1. Determine the size and location of the structure, and the restrictions for building it.
  2. Obtain construction details for garages and sheds larger than 120 square feet. The details include:
    • Structure size
    • Structure height
    • Construction type
    • Walls
    • Foundation
    • Roof
    • Door header
    • Roof pitch
  3. Apply for a building permit. The applications are available at Oak Creek City Hall or from our website at through the Inspection Department page.


Up to two accessory buildings are allowed on any single-family lot.
No pole barns or block buildings are allowed on single family residential lots less than 21,780 square feet.


For structures bigger than 120 square feet, please complete, in detail, the Accessory Building Permit Application. Submit the application along with a copy of the plat of survey for your property showing the location of the accessory structure. For a shed more than 120 square feet, the fee is $50 plus a $5 administrative fee. The fee for a an Accessory Structure greater than 240 square feet is 20 cents per square foot plus a $50 plan review fee and a $5 administrative fee.

There is no permit required for sheds 120 square feet or smaller. However, they still must meet all requirements for accessory structures set forth in Sec. 17.0501. The structure must be at least 5 feet from any lot line, at least 10 feet from the residence, and may not be placed in any easement.

Please allow up to two weeks for the processing of your permit.

If you have any questions regarding the requirements, please call (414) 766-7000 between the hours of 7:30 a.m. to 4 p.m.


  • The maximum square footage of detached accessory buildings or garages on single family residential lots, less than 21,780 square feet (less than 1/2 acre), shall be the greater of 720 square feet or 75% of the square footage of the living area (excluding attached garages) within the principal building; but in no even shall the detached accessory building be larger than 1,000 square fee. No pole or block buildings will be permitted on single family residential lots less than 21,780 square feet)
  • The maximum square footage of detached accessory buildings or garages on a single family residential lot greater than 1/2 acre (21,780 square feet) shall be the greater of 720 square feet or 75% of the square footage of living area (excluding attached garages) within the principal building; but in no event shall the detached accessory building be larger than 1,200 square feet.


  • A building greater than 720 sq. ft. (up to 1000 sq. ft.) must be at least 20 feet from the house, and at least 15 feet away from any lot line.
  • A building 720 square feet or less must be at least 10 feet away from the house, and at least 5 feet away from any lot line.
  • If an accessory building 720 sq. ft. or less is constructed with a one-hour fire rating per ILHR 21.08, or Section 30.43 of the Municipal Code, it may be located a minimum of 5 feet away from the house.
  • An accessory building is not allowed to be located in the front yard or street yard



  • The floor in all accessory structures larger than 200 square feet must be concrete. They may be built with a continuous floating slab of reinforced concrete at least 4 inches thick. Reinforcement must be provided by 10-guage 6 x 6 inch wire mesh, or an approved fiber mesh system.
  • The slab must have a thickened edge all around, 8 inches wide and 8 inches below the top of the slab. The thickened edge must have two No. 4 horizontal reinforcement bars placed at the center. The lower reinforcement bar must be set 2 inches above the bottom of the thickened edge, and the upper reinforcement bar must be set 6 inches above the bottom of the thickened edge.
  • Exterior wall curbs are required not less than 4 inches above the finished ground grade adjacent to the garage. Six-inch bolts, 3/8 inches in diameter, with nuts and washers attached, must be embedded 3 inches into the concrete curb of detached garages, 8 feet on center.
  • Storage sheds with a floor area less than 200 square feet do not require a concrete foundation. However, they must be anchored to the ground by an appropriate method.


The concrete floor must be sloped toward the exterior garage door or opening. No openings or pits in the floor are allowed, except for drainage. A minimum of 3 inches of gravel or equivalent must be placed below the floor.


Studs may have a maximum spacing of 24 inches on center.
Diagonal corner bracing shall be installed on both walls at each corner. Diagonal corner bracing may be applied on the inside surface of studs.
Corner posts may be constructed with 2-inch by 4-inch studs,, or with a single 4-inch by 4- inch stud.
Collar beams at the top plate, and collar ties in the upper one third of the roof, must be installed with a maximum spacing of 48 inches on center. Collar beams may be 2 inches by 6 inches. Collar ties must be at least 2- by 4-inch for roof slopes less than 4 inches per foot. A 1 x 6 inch collar tie may be used for roof slopes 4 inches per foot or greater.
Garage roofs must be framed in accordance with the applicable requirements of section COMM 21.28.
Wall height of accessory buildings:
On lots less than 21,780 square feet (1/2 an acre), the height of any exterior wall of an accessory building shall not exceed 9 feet. The end walls of buildings with a gable or gambrel roof are an exception.
On lots 21,780 square feet or more, the exterior walls shall not exceed 12 feet, the end walls of buildings with a gable or gambrel roof being an exception. 


All open flame equipment must be effectively separated by not less than a one-hour fire-resistive wall, floor or ceiling. Suspended furnaces or direct fired units that are fired with liquid fuel or gas may be used without an enclosure, provided that they are at least 7 feet above the floor, and at least 6 inches away from any combustible wall or ceiling. All units must be supported by noncombustible brackets or hangers, or installed per manufacturer’s specifications.


Over 200 square feet:
  • Footing and foundation (Before installation of concrete)
  • Rough framing (if you plan to finish the inside walls)
  • Final
Less than 200 square feet:
  • Foundation (to determined how the structure is anchored to the ground)
  • Final

Please note: 

The contractor or owner should arrange for inspections 24 hours in advance by calling City Hall at (414) 766-7000.

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