districts, such as Manhattan in New York, front walls of buildings at the street line may be limited to a specified height or number of stories. This height is also called base height which is only required if the building will exceed maximum base height. Above that height, the buildings are required to set back behind a theoretical inclined plane, called sky exposure plane, which cannot be penetrated by the building's exterior wall. For the same reason, setbacks may also be used in lower density districts to limit the height of perimeter walls above which a building must have a pitched roof or be set back before rising to the permitted height. In many cities, building setbacks add value to the interior real estate adjacent to the setback by creating usable exterior spaces. These setback terraces are prized for the access they provide to fresh air, skyline views, and recreational uses such as gardening and outdoor dining. In addition, setbacks promote fire safety by spacing buildings and their protruding parts away from each other and allow for passage of firefighting apparatus between buildings. In the United States, setback requirements vary among municipalities. For example, the absence of sky exposure plane provisions in Chicago's Zoning Code makes the Chicago skyline quite different from the skyline of New York where construction of tall buildings was guided by the zoning ordinance since 1916. The New York City Zoning Ordinance also provided another kind of setback guideline, one that was intended to increase the amount of public space in the city. This was achieved by increasing the minimum setback at street level, creating in each instance an open space, often referred to as plaza, in front of the building. See also Height of Buildings Act of 1910 (Washington DC) Urban canyon References Further reading Alexander, Christopher. A Pattern Language. Oxford University Press, 1977. Koolhaas, Rem. Delirious New York. Monacceli Press, reprint 1997. External links NYC Zoning History Architectural elements Real property law Urban studies and planning terminology de:Geschoss (Architektur)#Staffelgeschoss el:Ρετιρέ