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Add an Accessory Building to Your Property

storage shedAn accessory structure is a detached building that is incidental to and dependent upon the main building on the property. Examples of common accessory structures include a garden shed, play house, shop building, or detached carport or garage.

The following issues need to be determined before adding an accessory structure to your property:

  • What is the maximum size allowed?
  • What is the height of the structure?
  • Is a building permit required?
  • Where can the structure be located?

Distance between the Structure and Property Lines

Accessory structures like garden or tool sheds, garages, and playhouses must meet maximum height and size and minimum setback requirements. You may also need a building permit.

You can only build an accessory structure when there is a main use building on your property. For residential uses, this typically means there needs to be a dwelling on the property. Generally, you cannot build an accessory building by itself on an otherwise vacant lot.

The outside wall of the accessory building is also required to be set back a specific distance from your property lines. The table below lists the minimum setback required for an accessory building based on its location on the property and its height.

Minimum Distance Required between a Fire-Rated Structure and the Property Line

Structure Height of accessory structure
0′–4' 4–9' 10' 11' 12' 13' 14' 15'
Rear yard 0 0 1' 2' 3' 4' 5' 6'
Rear yard next to an alley in the rear yard 1' 1' 1' 2' 3' 4' 5' 6'
Any yard next to a local street 0 12' 12' 12' 12' 12' 12' 12'
Any yard next to a collector or arterial street (generally carries more traffic than local streets) 0 20' 20' 20' 20' 20' 20' 20'
Interior side yard 5' 5' 5' 5' 5' 5' 5' 5'
Interior side yard and the accessory structure is part of a fence 0 0 0 0 0 0 0 0

Building code requires accessory structures that do not have a fire rating to be a minimum of three feet from the property line regardless of the structure’s height or location.

Maximum Size

All accessory structures in a rear yard can only cover up to 25 percent of that rear yard area.

In addition, the square footage of the main building determines the maximum size of an accessory building in residential zones (except Residential Agriculture zone) as follows:

Main building gross floor area Maximum accessory building size
1,200 square feet or less 600 square feet
More than 1,200 square feet 1,000 square feet or 50% of main building, whichever is less

Height

Accessory structures are limited to 15 feet in height. Any structure over 10 feet in height requires a building permit.

For building permits, height is measured from the finished floor level. For determining size and location on the property, the height is generally measured from the ground.

Height of a structure with a pitched roof is measured to halfway between the peak and the eave of the pitched roof as shown below.

12-foot-tall building
Example of how to measure the height of a structure

Building Permit Exemption

You need a residential building permit for your structure unless it meets all the following criteria:

  • It is used as a tool shed, storage shed, playhouse or similar use which do not include vehicle storage or residential occupancy.
  • The floor area is less than 200 square feet.
  • The height is less than 10 feet.

You will need to submit building plans as part of the permit process. The City provides pre-approved building plans for you to download.

Front yard, side yard, back yard definitions
Example of the definition of front yard, side yard, and back yard in relation to the street, house, and property lines