Zoning is a North American term for a system of land-use regulation. The word is derived from the practice of designating permitted uses of land based on mapped zones which separate one part of a community from another. Zoning regulations fall under the police power rights governments may exercise over real property. Theoretically, the primary purpose of zoning is to segregate uses that are thought to be incompatible; in practice, zoning is used as a permitting system to prevent new development from harming existing residents or businesses. Zoning is commonly controlled by local governments such as counties or municipalities.

Zoning commonly includes regulation of the kinds of activities which will be acceptable on particular lots (such as open space, residential, agricultural, commercial or industrial), the densities at which those activities can be performed (from low-density housing such as single family homes to high-density such as high-rise apartment buildings), the height of buildings, the amount of space structures may occupy, the location of a building on the lot (setbacks), the proportions of the types of space on a lot (for example, how much landscaped space and how much paved space), and how much parking must be provided.

Most zoning systems have a procedure for granting variances (exceptions to the zoning rules), usually because of some perceived hardship due to the particular nature of the property in question.

Types of residential zones would be R1 for single-family homes, R2 for two-family homes, and R3 for multiple-family homes.

Types of Zoning

Zoning codes have evolved over the years as urban planning theory has changed, legal constraints have fluctuated, and political priorities have shifted. The various approaches to zoning can be divided into four broad categories: Euclidean, Performance, Incentive, and Design-based.

Euclidean zoning

Named for the type of zoning code adopted in the town of Euclid, Ohio (and later challenged and upheld in the U.S. Supreme Court in 1926, see below), Euclidean zoning codes are by far the most prevalent in the United States, used extensively in small towns and large cities alike. Also known as "Building Block" zoning, Euclidean zoning is characterized by the segregation of land uses into specified geographic districts and dimensional standards stipulating limitations on the magnitude of development activity that is allowed to take place on lots within each type of district. Typical types of land-use districts in Euclidean zoning are: residential (single-family), residential (multi-family), commercial, and industrial. Uses within each district are usually heavily prescribed to exclude other types of uses (residential districts typically disallow commercial or industrial uses). Some "accessory" or "conditional" uses may be allowed in order to accommodate the needs of the primary uses. Dimensional standards apply to any structures built on lots within each zoning district, and typically take the form of setbacks, height limits, minimum lot sizes, lot coverage limits, and other limitations on the building envelope.

Euclidean zoning is preferred by many municipalities due to its ease of implementation (one set of explicit, prescriptive rules), long-established legal precedent, and familiarity to planners and design professionals. Euclidean zoning has been heavily criticized, however, for its lack of flexibility and institutionalization of now-outdated planning theory.

Performance zoning

Performance zoning uses performance-based or goal-oriented criteria to establish review parameters for proposed development projects in any area of a municipality. Performance zoning often utilizes a "points-based" system whereby a property developer can apply credits toward meeting established zoning goals through selecting from a 'menu' of compliance options (some examples include: mitigation of environmental impacts, providing public amenities, building affordable housing units, etc.). Additional discretionary criteria may also be established as part of the review process.

Performance zoning is known for its high level of flexibility. However, performance zoning can be extremely difficult to implement and may require a high level of discretionary activity on the part of the supervising authority. For this reason, performance zoning has not been widely adopted and is usually limited to specific categories within a broader prescriptive code when found.

Incentive zoning

First implemented in Chicago and New York City, incentive zoning is intended to provide a reward-based system to encourage development that meets established urban development goals. Typically, a base level of prescriptive limitations on development will be established and an extensive list of incentive criteria will be established for developers to adopt or not at their discretion. A reward scale connected to the incentive criteria provides an enticement for developers to incorporate the desired development criteria into their projects. Common examples include FAR (floor-area-ratio) bonuses for affordable housing provided on-site and height limit bonuses for the inclusion of public amenities on-site. Incentive zoning has become more common throughout the United States during the last 20 years.

Incentive zoning allows for a high degree of flexibility, but can be complex to administer. The more a proposed development takes advantage of incentive criteria, the more closely it has to be reviewed on a discretionary basis. The initial creation of the incentive structure in order to best serve planning priorities can also be challenging and often requires extensive ongoing revision to maintain balance between incentive magnitude and value given to developers.

Design-based zoning

Design-based zoning relies on inter-related schedules of rules to be applied to development sites according to both prescriptive and discretionary criteria. These criteria are typically dependent on lot size, location, proximity, and other various site- and use-specific characteristics.

Design-based codes offer considerably more flexibility than Euclidean codes, but can be very complex to create and administer. Design-based codes have not been widely adopted in the United States and are often criticized as overly-constraining and difficult to interpret where they have been used.

One example of a recently adopted code with design-based features is the Land Development Code adopted by Louisville, Kentucky in 2003. This zoning code created "form districts" for Louisville Metro. Each form district was intended to recognize that some areas of the city were suburban in nature, and some urban. Building setbacks, heights and design features vary according to the form district. As an example, in a "traditional neighborhood" form district, a maximum setback might be 15 feet from the property line, while in a suburban "neighborhood" there might be no maximum setback at all.

Constitutional challenges

There have been notable legal challenges to zoning regulations. In 1926 the United States Supreme Court upheld zoning as a right of U.S. states (typically via their cities and counties) to impose on landowners. The case was Village of Euclid, Ohio v. Ambler Realty Co. (often shortened to Euclid v. Ambler), 272 U.S. 365 (1926). The village had zoned an area of land held by Ambler Realty as a residential neighborhood. Ambler argued that it would lose money because if the land could be leased to industrial users it would have netted a great deal more money than as a residential area. Euclid won, and a precedent was set favorable to local enforcement of zoning laws.

The Euclid case was a facial challenge, meaning that the entire scheme of regulation was argued to be unconstitutional under any set of circumstances. The United States Supreme Court justified the ordinance saying that a community may enact reasonable laws to keep the pig out of the parlor, even if pigs may not be prohibited from the entire community.

Specific zoning laws have been overturned in some other U.S. cases where the laws were not applied evenly (violating equal protection) or were considered to violate free speech. In the Atlanta suburb of Roswell, Georgia, an ordinance banning billboards was overturned in court on such grounds. It has been deemed that a municipality's sign ordinance must be content neutral with regard to the regulation of signage. The City of Roswell, Georgia has now instituted a sign ordinance that regulates signage based strictly on dimensional and aesthetic codes, rather than an interpretation of a sign's content (i.e. use of colors, lettering, etc.).

Exclusionary zoning

Zoning has long been criticized as a tool of racial and socio-economic exclusion and segregation, primarily through minimum lot-size requirements and land-use segregation (sometimes referred to as "environmental racism"). Early zoning codes were often explicitly racist. Exclusionary practices remain common among suburbs wishing to keep out those deemed socioeconomically or ethnically undesirable: for example, representatives of the city of Barrington Hills, Illinois once told the Real Estate section of the Chicago Tribune that the city's 5-acre minimum lot size helped to "keep out the riff-raff.”

http://en.wikipedia.org/wiki/Zoning