Zoningdivision of an area into sub-areas, called zones.
Zoning is a system of land use regulation which designates the permitted uses of land based on location. One purpose of zoning is to prevent new development from harming existing residents or businesses.
Zoning commonly includes regulation on 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 (low density housing such as single family homes to high density such as apartment buildings), the height of buildings, the amount of space structures may occupy by limiting how close a building may be from the edge of the lot, 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.
Arguments against zoning generally center around the concept of regulatory taking. In the United States, takings are forbidden by the Fifth Amendment, unless there is due process and compensation. The Supreme Court has ruled that this eminent domain process is unnecessary unless the owner would lose "substantially all" of the use of the land, which generally means that the land must be taken outright for this to be invoked.
Land use zoning was once considered an important tool in the treatment of certain social ills, a part of the larger concept of social engineering. Some jurisdictions attempting to manage growth have turned to comprehensive planning to coordinate the growth of housing, industry, commercial with the impacts growth has on issues such as transportation, utilities, recreation, schools, fire protection and police protection.
New York City adopted the first zoning regulations to apply city-wide in 1916 as a reaction to construction of The Equitable Building (which still stands at 120 Broadway). The building towered over the neighboring residences and cast long shadows that diminished the quality of life for the people in the affected area. These laws written by a commission headed by Edward Basset and signed by Mayor John Purroy Mitchel became the blueprint for the rest of the country (partly because Edward Basset headed the group of planning laws that wrote The Standard State Zoning Enabling Act, which was accepted almost without change by most states) and by the late 1920s most of the nation would have developed a set of zoning regulations that met the needs of the locality. New York went on to develop ever more complex set of zoning regulations, including floor area ratio regulations, air rights and others according to the density-specific needs of the neighborhoods.
There was a notable legal challenge to zoning regulations. In 1926 the 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. Amber), 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.
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 billboardss was overturned in court on such grounds.
Other uses of the concept of zoning
In many cities, fares for public transport depend on the number of zones in which a rider travels. London has recently zoned the central city for a high toll called the London Congestion Charge (£5 GBP) to reduce traffic.
Telephone service may be zoned so that calls to the immediate area are free, calls to adjoining zones incur a small toll and calls to the other side of the metro area incur a somewhat higher toll even though they may all be considered a "local" (non-long-distance) call.
Zoning may be implemented in air conditioning systems so that heating and cooling go where they are needed. For example, a house may be fitted with two thermostats,one for upstairs and one for downstairs. Residential HVAC zoning is most often used in radiant heating systems in the floor or ceiling, or with regular radiators.
Irrigation sprinklers are almost always zoned, so that water pressure does not drop when the entire system is turned on at once. It is also extremely useful for controlling flow rates to areas with plants that need more or less water, or frequency of watering.
Burglar alarm systems are often zoned as well, expecially in the case where different people will have different access levels to different rooms. Fire alarms are also sometimes done in this manner, though only in particular situations where fire cannot spread beyond a firewall or other method of containment.
See also: variance (land use)