Tower block

• 1. Introduction

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  A tower block can rise so high that a city must rewrite its rules around it. In the United States, the National Fire Protection Association draws the line at 75 feet, about seven stories, the point where height starts to seriously affect how people escape a fire. Most building engineers, inspectors, and architects settle on that same figure, about 23 meters. Yet there is no clean border between a tower block and a skyscraper. A building of forty or more stories, taller than 150 meters, is generally counted as the latter. The terms multiply depending on where you stand. The same kind of building is a high-rise, an apartment tower, a residential tower, a block of flats, an office tower. In British English it is a tower block, sometimes shortened to MDU, for multi-dwelling unit. How did so much of humanity end up living stacked vertically? Why do these towers inspire both glossy luxury and bitter stigma? And what does it take to keep people safe so far above the ground?

• 2. Built On Two Inventions

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  The elevator, or lift, is what made the tall building possible. High-rise construction also depended on cheaper, more abundant building materials. Reinforced concrete and steel form the structural backbone of these buildings. Most North American-style skyscrapers use a steel frame, while residential blocks tend to be built of concrete.

  Height invites a particular set of dangers, especially in seismically active regions. Soils carry their own geotechnical risk factors, such as high compressibility or bay mud, which complicate the work of structural and geotechnical engineers. Firefighters face serious challenges in any high-rise emergency. The building standpipe system, HVAC for heating, ventilation and air conditioning, fire sprinkler systems, and the question of how to evacuate by stairwell and elevator all become problems of life and death.

  Wind shapes the form of these towers. Studies are often required to address pedestrian wind comfort and wind danger near the base. To reduce wind exposure, to let more daylight reach the ground, and to look more slender, many high-rises are designed with setbacks. That density pays off where land is scarce. Apartment blocks hold more people per unit of land and lower the cost of municipal infrastructure, which is why they appear in virtually every densely populated city on earth.

• 3. Towers Of The Ancient World

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  Ancient Rome stacked its poor into the sky long before the elevator existed. The insulae of Rome and other cities of the Roman Empire might reach ten or more stories, with one reportedly served by 200 stairs. Poorly built insulae collapsed often enough that several emperors, starting with Augustus, set height limits, though the rules were frequently ignored. Shops or wealthy families occupied the lower floors, while the upper stories were rented to the lower classes. Surviving Oxyrhynchus Papyri record seven-story buildings even in provincial towns, including third century Hermopolis in Roman Egypt.

  Fustat, the early capital of Arab Egypt, held high-rise residential buildings of around seven stories said to house hundreds of people. Writing in the 10th century, Al-Muqaddasi compared them to minarets. In the early 11th century, Nasir Khusraw described some rising up to 14 stories, topped with roof gardens watered by ox-drawn wheels. By the 16th century, Cairo had apartment buildings where the two lower floors held commerce and storage while the floors above were rented to tenants.

  Medieval skylines bristled with urban towers built for defense and display. The residential Towers of Bologna once numbered between 80 and 100, the tallest still standing at 97.2 meters. A Florence law of 1251 capped urban buildings below 26 meters and took effect at once. Even the medium-sized town of San Gimignano is known to have had 72 towers, some reaching 51 meters.

• 4. Vertical Living, Many Cultures

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  The Hakka people of southern China built communal homes designed to be defended. The weilongwu and the enclosed, fortified earth buildings called tulou, often shortened to yuanlou, rose between two and five stories and could house up to 80 families. The oldest surviving tulou dates from the 14th century.

  Shibam, in Yemen, raised its towers from mud brick in the 16th century. About five hundred of its houses are tower houses, climbing five to sixteen stories, with one or two apartments per floor. The technique protected residents from Bedouin attacks. Though Shibam has stood for roughly two thousand years, most of its houses date from the 16th century. Some of its mud buildings rise more than 30 meters, the tallest of their kind in the world, earning the city the nickname "Manhattan of the desert" and praise as one of the oldest examples of urban planning built on vertical construction.

  The modern engineer's definition of a high-rise grew out of the fire truck. Magirus showed the first cogwheel sliding ladder in 1864. A horse-drawn turntable ladder reaching 25 meters arrived in 1892, and Magirus motorized the extension ladder in 1904. A maximum of 22 meters for the highest floor was a common limit in building regulations then, and it still holds in Germany today. Turntable ladders later reached 32 meters, so a 30-meter limit appears in some regulations, such as Switzerland's. Any building taller than a city's usual ladders must install extra fire safety equipment, which is why high-rises occupy their own section of building codes worldwide.

• 5. The Modernist Dream

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  Le Corbusier's Unité d'Habitation gave the residential tower block its signature concrete form. He repeated the design in several European cities, beginning with his Cité radieuse in Marseille between 1947 and 1952. With steel for framing unavailable in post-war France, it was built from béton brut, rough-cast concrete. These towers became the standard tool for rehousing urban populations displaced by slum clearances and urban renewal.

  After the Second World War, high-rise projects rejected the classical look of early skyscrapers in favor of a uniform international style. Many older skyscrapers were redesigned or demolished, among them New York's Singer Building, once the world's tallest. Then, from the 1980s, Postmodernism, New Urbanism, and New Classical Architecture brought a more classical approach back to skyscraper design. The field today spans many movements, from organic and sustainable to neo-futurist, deconstructivist, blob, streamline, Art Deco, and revivalist.

  The tallest high-rise apartment building in the world now stands on Billionaires' Row in Midtown Manhattan. Central Park Tower rises to 1,550 feet, with its highest occupied floor at 1,417 feet.

• 6. Streets In The Sky

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  Britain in the 1960s and 1970s tried to lift the city street into the air. The style called streets in the sky replaced run-down terraced housing and added modern improvements like inside toilets, along with shops and community facilities inside high-rise blocks. London examples include Trellick Tower, Balfron Tower, Broadwater Farm, Robin Hood Gardens, and Keeling House, with more in Leeds, Sheffield, and Runcorn. Alison and Peter Smithson designed Robin Hood Gardens. In 2005 a 20-year program was set to demolish and replace the Aylesbury Estate in south London, built in 1970. The Hulme Crescents in Manchester were the largest social housing scheme in Europe when built in 1972, yet lasted just 22 years and gathered one of the worst reputations in British social housing.

  The ideal rarely worked in practice. Unlike a real street, these walkways were not thoroughfares and often dead-ended several stories above the ground. They lacked a steady flow of passers-by, and the walkways and stairwells could not be seen from anywhere else, so nothing deterred crime. There were no "eyes on the street" of the kind Jane Jacobs called for in The Death and Life of Great American Cities. The Unité d'Habitation in Marseille worked better, its fifth-floor walkway holding a shop and a café.

  A related idea placed the tower not on the street but within green space. Towers in the park surrounds a high-rise with landscaped land so the building does not directly front the street. The concept drew on Le Corbusier's Plan Voisin, an outgrowth of the Garden city movement meant to ease urban congestion. It spread across North America, Europe, and Australia, peaking in the 1960s alongside prefabrication. By the early 1970s, critics including urban planners were calling these projects "ghettos." A neighborhood like St. James Town, first meant for young single middle-class residents, lost its appeal and grew poorer fast. The layout was blamed for making residents feel unsafe and for hampering essential services, especially law enforcement. The older idea of the microdistrict ran differently. It dates to the 1920s, when rapid Soviet urbanization favored compact residential complexes with schools, shops, entertainment, and green spaces, seen as a way to build a collective society.

• 7. A Region By Region Atlas

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  Hong Kong's land is so expensive that more than 60 percent of residents live in apartments, many of them condominiums. In 2020, some 2,112,138 people were identified as residents of public housing, 28 percent of the total population. Residential tower complexes are common across high-density Asia, from China and India to Singapore, Japan, and South Korea. Writing in 2012, Sarah Williams Goldhagen praised firms like WOHA in Singapore, Mass Studies in Seoul, and Amateur Architecture Studio in Hangzhou for turning residential towers into "vertical cities in the sky," though she noted none of these humane buildings are affordable housing.

  The 2012 Pritzker Prize went to the Chinese architect Wang Shu. His Vertical Courtyard Apartments in Hangzhou are six 26-story towers, designed so that every third story opens into a private courtyard, giving each resident the illusion of living on the second floor. In South Korea, where tower blocks are called Apartment Complexes, the first rose after the Korean War to house a growing urban population. Roughly 80 percent of Seoul's residents now live in apartment complexes, which make up 98 percent of recent residential construction. Samsung Tower Palace in Seoul is the tallest apartment complex in Asia.

  The Eastern Bloc built tower blocks in vast numbers to house postwar populations, mostly through the 1950s, 1960s, and 1970s. Many follow the socialist realist style, and the blocky buildings of that era are known colloquially as Khrushchyovka. The longest examples are striking, like the falowiec in Gdansk's Przymorze Wielkie district, 860 meters long with 1,792 flats, the second longest housing block in Europe. In Romania, standardized blocuri spread under the systematisation programme of Nicolae Ceausescu, while in Czechoslovakia the panelak emerged from postwar housing shortage and party ideology. Across the former Warsaw Pact states of the European Union, most people live in flats in Latvia at 64.4 percent, Estonia at 60.6 percent, and Lithuania at 59.5 percent, according to Eurostat.

  In North America, Toronto holds the second largest concentration of high-rise apartment buildings on the continent, after New York. Some of the first residential towers were the Castle Village towers in Manhattan, finished in 1939, whose cross-shaped design was copied in Parkchester and Stuyvesant Town. The wealthiest urban neighborhood in the United States is the Upper East Side, full of high-rise apartments. In Australia, high-rise living was limited to the Sydney CBD until the 1960s, when public housing tenants were placed in new towers in Sydney and Melbourne.

• 8. When The Towers Fell From Favor

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  Ronan Point collapsed in 1968, and British attitudes toward tower blocks never fully recovered. First built after the Second World War as a cheap way to replace 19th-century slums and war damage, the blocks were once seen as desirable. They quickly fell out of favor as they drew rising crime and social disorder. Lack of proper regulation left some posing a significant fire risk, and modern safety upgrades can be prohibitively expensive to retrofit. The Grenfell Tower fire in 2017 was partly blamed on council ignorance, after a local action group had complained about fire hazards years earlier without remedial work being done.

  Dublin tells a parallel story. The Ballymun Flats, built between 1966 and 1969, comprised seven 15-story towers along with nineteen 8-story and ten 4-story blocks. They were the "seven towers" of the U2 song "Running to Stand Still," and they have since been demolished. A heroin epidemic struck working-class areas of Dublin in the 1980s and early 1990s, hitting these flats hard. In Northern Ireland, the first tall council housing blocks on the island were a pair of point blocks in East Belfast's Cregagh estate, completed in 1961. Divis Tower, built in 1966, still stands and was for decades Ireland's tallest residential building, until the privately owned Obel Tower surpassed it.

  The American experiments fared no better. Government efforts in the 1960s and 1970s to house the poor in high-rises broadly failed. Built in the tower in the park style, projects like Cabrini-Green and Robert Taylor Homes in Chicago and the Desire Projects in New Orleans fell to ghettofication and are being torn down or replaced. The former Pruitt-Igoe complex in St. Louis was demolished in the 1970s. Where the public projects collapsed, commercial high-rises flourished, driven by high land prices and the housing boom of the 2000s. Newer forms now reach toward the green tower block, fitted with living plants, green roofs, or solar panels, suggesting the next chapter is being written on the rooftops.