A zoning ordinance is the formal codification of land use policies for a city, district, county, or other unit of government. The goal of a zoning ordinance is to establish permitted uses for land covered by the ordinance, and to distinguish between different types of uses which may be incompatible. In addition to defining specific types of land use, zoning ordinances also usually divide a region into “zones” where certain types of permitted use can occur, which explains the name.
Historically, once people bought land, they were largely allowed to do whatever they wanted with it. Someone could build a house, install a tannery, start a factory, or utilize an area for farming. Over time, cities began to put building restrictions in place for the purpose of protecting public safety, and by the early 1900s, several cities had specifically created zoning ordinances to address varied types of land use.
Within a zoning ordinance, the law usually distinguishes between residential, high density residential, commercial, light industrial, industrial, agricultural, and other types of land use. The law provides clear definitions, which usually include the amount of square footage which can be constructed within a specific zone, and the types of activities which may take place in each zone. In a conventional residential district, zoning is usually designed to create low to medium density, which might include duplexes and single family dwellings. By contrast, commercial or high density residential might allow for many more units within the same space.
When a zoning ordinance is formulated, it usually reflects the fact that people find certain types of activities conflicting. For example, a factory would not be a welcome addition to a residential neighborhood, while in a live-work district which included mixed commercial and residential zoning, an office tower might be viewed as a source of conflict. Zoning ordinances are designed to separate out different types of use to prevent conflict.
These ordinances may also preserve certain aesthetic ideals, such as a desire to keep structures in residential neighborhoods under three stories tall, and in some cases public safety issues may be addressed as well. For example, a zoning ordinance may mandate the installation of specialized street lights in commercial districts so that it will be safer to be out at night.
Zoning ordinances are constantly being changed to reflect shifting beliefs about how land should be used, and how communities should deal with changing social norms. The most current version is usually on file at local government offices, and as a general rule, the zoning of a piece of real estate can only be changed when the owner applies for a change of zoning, in which case the owner will usually need to present supporting evidence for the change at a public hearing.