Skyscraper

A skyscraper is a very tall, continuously habitable building. There is no official definition or a precise cutoff height above which a building may clearly be classified as a skyscraper. However, as per usual practice in most cities, the definition is used empirically, depending on the relative impact of the shape of a building to a city's overall skyline (even though at least 20 stories or more are required for a building to be considered a skyscraper). Thus, depending on the average height of the rest of the buildings and/ or structures in a city, even a building of 80 meters height (approximately 262 ft) may be considered a skyscraper provided that it clearly stands out above its surrounding built environment and significantly changes the overall skyline of this particular city.

The word skyscraper was first applied to such buildings in the late 19th century, reflecting public amazement at the tall buildings being built in Chicago and New York City. The structural definition of the word skyscraper was refined later by architectural historians, based on engineering developments of the 1880s that had enabled construction of tall multi-story buildings. This definition was based on the steel skeleton—as opposed to constructions of load-bearing masonry, which passed their practical limit in 1891 with Chicago's Monadnock Building. Philadelphia's City Hall, completed in 1901, still holds claim as the world's tallest load-bearing masonry structure at 167 m (548 ft). The steel frame developed in stages of increasing self-sufficiency, with several buildings in Chicago and New York advancing the technology that allowed the steel frame to carry a building on its own. Today, however, many of the tallest skyscrapers are built more or less entirely with reinforced concrete. In the United States today, it is a loose convention to draw the lower limit on what is a skyscraper at 150 meters. Elsewhere, though, a shorter building will sometimes be referred to as a skyscraper, especially if it is said to "dominate" its surroundings. Thus, calling a building a skyscraper will usually, but not always, imply pride and achievement.

Originally, skyscraper was a nautical term for a tall mast or sail on a sailing ship. A skyscraper taller than 300 meters (1,000 ft) may sometimes be referred to as a supertall.

The somewhat arbitrary term skyscraper should not be confused with the slightly less arbitrary term highrise, defined by the Emporis Standards Committee as "A high-rise building is a multi-story structure with at least 12 floors or 35 meters (115 feet) in height." . All skyscrapers are highrises, but only the tallest highrises are skyscrapers. Habitability separates skyscrapers from towers and masts. Some structural engineers define a highrise as any vertical construction for which wind is a more significant load factor than weight is. Note that this criterion fits not only highrises but some other tall structures, such as towers.

Pumps and storage tanks are used to maintain water pressure at the top of skyscrapers.