High-rise buildings became possible with the invention of the elevator (lift) and cheaper, more abundant building materials. Buildings between and 491 feet (23 m to 150 m) high are, by some standards, considered high-rises. Buildings taller than 492 feet (150 m) are classified as skyscrapers. The average height of a level is around 13 feet (4 m) high, thus a 79 foot (24 m) tall building would comprise 6 floors.
The materials used for the structural system of high-rise buildings are reinforced concrete and steel. Most American style skyscrapers have a steel frame, while residential tower blocks are usually constructed out of concrete.
Although the exact definition is immaterial, various bodies have tried to define what 'high-rise' means:
High-rise structures pose particular design challenges for structural and geotechnical engineers, particularly if situated in a seismically active region or if the underlying soils have geotechnical risk factors such as high compressibility or bay mud. They also pose serious challenges to firefighters during emergencies in high-rise structures. New and old building design, building systems like the building standpipe system, HVAC systems (Heating, Ventilation and Air conditioning), fire sprinkler system and other things like stairwell and elevator evacuations pose significant problems.
High-rise apartment buildings had already flourished in antiquity: the insulae in ancient Rome and several other cities in the Roman Empire, some of which might have reached up to 10 or more stories, one reportedly having 200 stairs. Because of the destruction caused by poorly-built high-rise insulae collapsing, several Roman emperors, beginning with Augustus (r. 30 BC - 14 AD), set limits of 20-25 metres for multi-story buildings, but met with limited success, as these limits were often ignored despite the likelihood of taller insulae collapsing.
The 16th century Yemeni city of Shibam is made up of over 500 tower houses, each one rising 5 to 11 storeys high, with each floor having one or two apartments. The city had the first high-rise mudbrick buildings, with some of them being over over in height. These remain the tallest high-rise mudbrick buildings in the world. The tallest building in the city is the mudbrick minaret which stands at tall.