Generally, zoning ordinances state that landowners may use their land for a principal permitted use and for activities that are accessory to that use. Accessory uses are uses of land that are found on the same parcel as the principal use but are subordinate and incidental. The term "accessory use" also applies to accessory structures. For example, a detached garage may be accessory to the residential use of a property because it reasonably related to the principal use as a place for a homeowner to store his automobile and subordinate to the principal permitted use of the house.
Zoning ordinances ordinarily specify a range of accessory uses that landowners have come to expect as customary when they purchase their property because they allow for additional beneficial use. Examples for residential properties include garages, storage sheds and fences, and, more recently, satellite dishes. At the same time, accessory uses that are not consistent with the expectations of surrounding landowners should be limited or prohibited altogether.
One common controversy associated with accessory use is the question of whether such a use can be built on a lot before a principal use is established. For example, can a garage or storage shed be built before the house; or can a dog house be built on a vacant residential lot? Without specific language permitting the accessory use to “stand alone,” an accessory use is considered unlawful until the accompanying principal use or structure is established.
Gary D. Taylor, Iowa State University