The primary purpose of zoning is to segregate uses that are thought to be incompatible. In practice, zoning is used to prevent new development from interfering with existing residents or businesses and to preserve the “character” of a community.
Zoning is commonly controlled by local governments such as counties or municipalities, though the nature of the zoning regime may be determined or limited by state or national planning authorities or through enabling legislation.
The United States and other federal countries are similar. Zoning and urban planning in France and Germany are regulated by national or federal codes. In the case of Germany this code includes contents of zoning plans as well as the legal procedure.
Zoning may include 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, such as how much landscaped space, impervious surface, traffic lanes, and parking must be provided. In Germany, zoning usually includes building design, very specific greenspace and compensation regulations. The details of how individual planning systems incorporate zoning into their regulatory regimes varies though the intention is always similar. For example, in the state of Victoria, Australia, land use zones are combined with a system of planning scheme overlays to account for the multiplicity of factors that impact on desirable urban outcomes in any location.
Most zoning systems have a procedure for granting variances (exceptions to the zoning rules), usually because of some perceived hardship caused by the particular nature of the property in question.
Basically, urban zones fall into one of five major categories: residential, mixed residential-commercial, commercial, industrial and special (e. g. power plants, sports complexes, airports, shopping malls etc.). Each category can have a number of sub-categories. In Germany, e. g., each category has a designated limit for noise immissions (not part of the building code, but federal immissions code). In the United States or Canada, for example, residential zones can have the following sub-categories:
- Residential occupancies containing sleeping units where the occupants are primarily transient in nature, including: boarding houses, hotels, motels
- Residential occupancies containing sleeping units or more than two dwelling units where the occupants are primarily permanent in nature, including: apartment houses, boarding houses, convents, dormitories.
- Residential occupancies where the occupants are primarily permanent in nature and not classified as Group R-1, R-2, R-4 or I, including: buildings that do not contain more than two dwelling units, adult care facilities for five or fewer persons for less than 24 hours.
- Residential occupancies shall include buildings arranged for occupancy as residential care/assisted living facilities including more than five but not more than 16 occupants.