Planopedia

Zoning codes, in their simplest form, separate of land use into separate districts (or "zones"). Zoning codes, in effect, are the legal tool that cities use to determine what can be built, where. Zoning codes are also the implementation tool for the visions laid out by a variety of plans—including comprehensive plans, generals plans, specific plans, area plans, and more, depending on jurisdiction.

To understand the role of zoning in the context of planning practice, professional planners make a clear distinction between the process of planning, i.e., the process of defining a vision for the future, and the process of zoning, i.e., the regulatory tool by which those visions are achieved.

To achieve goals for the use of land, local governments in the United States use zoning codes to separate land under their jurisdictions into zones of allowable development. These zones are typically defined by three factors: 1) the use or activity taking place on the land or buildings built there, 2) the shape of buildings, e.g., height and relationship to the adjacent public right of way, and 3) the bulk of buildings, or the size of a building and how it orients on the property.

The first of those factors, the use of the land, is the fundamental concern of most, but not all, zoning codes in the United States, and thus will be the first consideration in almost every zoning designation. Zoning's concern with land use is responsible for the typical classifications that most people think of when they think of zoning: residential, commercial, industrial, agricultural, etc. There is no universal standard for zoning classifications, but many cities designate zoned uses with a familiar combination of letters and numbers—R for residential, R1 for single-family residential, C for commercial, I for industrial, and so on. 

Most zoning codes in the United States are described as Euclidean, named for the U.S. Supreme Court decision in Euclid v. Ambler (1926). That decision upheld the power of local governments to determine which properties or zones in towns are most suitable for specific uses—even if that control is potentially detrimental to the interests or desires of property owners. The separation of uses allowed by Euclid v. Ambler is the defining quality of Euclidean zoning codes, and it explains why most U.S. communities are defined by a uniformity of land uses, with residential areas of mostly single-family detached homes occupying most of the land in a community, while offices and retail areas are located in much smaller corners of the community. Exclusionary zoning is another frequently used term to describe the separation of uses enabled by Euclidean zoning (i.e., single-family residential developments are allowed while multi-family residential and retail and other forms of commercial development are excluded).

In recent decades, negative environmental and social effects from the country's tradition of Euclidean zoning have emerged, prompting reform of traditional zoning practices and inspiring innovative new land use control systems. In some cases, zoning reform uses the traditional tools of Euclidean zoning, but with far less restrictive prescriptions. Mixed use zones, where new buildings are allowed more than one use, have become popular, for example. Some cities, most notably Minneapolis, have ended zoning that only allows single-family zoning, allowing for forms of residential development, sometimes called Missing Middle Housing, that allow more than one unit to be included in a single building, or in accessory dwelling units located in separate buildings on the same property.

Zoning innovations that have also created entirely new systems for controlling the use of land and implementing local plans. Innovations include form-based zoning, which is probably the most widely adopted alternative to Euclidean zoning. Form-based zoning codes do as the name suggests by focusing on the form of buildings rather than their use, and thus represent a significant departure from U.S. planning tradition. Hybrid zoning combines elements of Euclidean and form-based codes. There is also Performance Zoning and Incentive Zoning. The Los Angeles Department of Planning provided an example of each of these zoning systems, and a few other approaches to zoning, in an article published in January 2014.

Zoning codes existed in their earliest form in Europe in the 19th century, but the first example of a zoning code in the United States was created by Los Angeles in 1908 to create districts prohibiting “nuisance” uses from mixing with residences. Credit for the first comprehensive zoning code in the United States goes to New York City, however. The 1916 Zoning Resolution addressed concerns about a new generation of high-rise construction blocking light and air from the streets. Zoning codes in the United States are a uniquely local power. While state laws can sometimes supersede local zoning laws, many U.S. municipalities retain total control over their zoning ordinance, and there is no federal law that controls urban land use.