By Jones Osborn II

The term "non-conforming use" is often used indiscriminately to refer to a zoning violation. This is actually a misuse of the word. In zoning law, a "non-conforming use" is a term of art with a very specific meaning.

Definition. A non-conforming use is a use that was legal when established but which later fails to conform because of a change in the law. This can occur when (a) new zoning is imposed on property which is previously unzoned, (b) the property was rezoned from an old zoning category to a new zoning category, or (c) the zoning category is not changed but the uses allowed in that category are changed. The term is normally not used to describe a run-of-the-mill zoning violation.

A non-conforming use can be legal or illegal, depending on the specifics of the law in the particular jurisdiction. As a general rule, however, a use which was legal when commenced remains legal after a change in the law. For example, suppose a gasoline service station was legally established under county zoning. If the land is later annexed into the city and rezoned for residential purposes, the gasoline station is normally permitted to continue to operate as a legal non-conforming use, even though it is located on land zoned for residential uses, because the use was legal when commenced. Billboards are another frequent non-conforming use because they are usually legal when constructed, but may later become non-conforming because of changes in the law designed to eliminate the perceived visual blight caused by billboards.

Laws allowing the continuation of non-conforming uses are based on ideas of fairness and equity, but they also have a Constitutional underpinning. Terminating an existing land use as a result of a change in the law raises the issue of a "taking" which might require the government to compensate the landowner. The U.S. Constitution, of course, provides that "private property shall not be taken for public use, without just compensation." Closing down an existing business because of a change in the zoning laws is often thought to be such a "taking."

This does not mean the property is completely exempt from the zoning laws, though. There are certain limitations.

Abandonment. The first limitation is that the non-conforming use must be continuous. If the property owner fails to use the property for the non-conforming use for a specified period of time, usually about six to 24 months (depending on the jurisdiction where the property is located), the use is considered abandoned and cannot be reinstituted. In the City of Phoenix, this period is 365 days. Under the Phoenix ordinance, if the use is discontinued for a year it cannot be started again.

Change in Use. Most ordinances provide that one non-conforming use cannot be changed into another non-conforming use. This means that the service station in the above example could not be converted into a bar or a factory.

On the other hand, some limited changes in use may be allowed. In the City of Phoenix, for example, one non-conforming use may be changed into another non-conforming use so long as the new use is "no more deleterious" to nearby properties and a use permit is secured from the City. This might allow a shoe repair shop to be converted into a flower shop, or something similar.

Expansion. Most jurisdictions impose limits on the amount of expansion a non-conforming use can undertake. In the City of Phoenix, for example, a non-conforming use cannot expand its floor area or the square footage of the lot devoted to the use by more than 50% of what it was when the use became non-conforming.

Conclusion. A non-conforming use is not just an ordinary zoning violation--it is a use which was legal when established but which later fails to conform because of changes in the law. Non-conforming uses are generally legal as long as they operate continuously, are not expanded beyond specified limits, and are not changed into another prohibited use.