What does a jumbo pencil have in common with a skyscraper? John Jacob Raskob, an American financier, held up a pencil and asked architect William Lamb a simple question: “How high can you make it so it won’t fall down?” The Empire State Building was the result.
Skyscrapers are a global symbol of power and wealth. Going vertical is also preferable when dealing with metropolitan area population density and the price of valuable city real estate. Yet the question Raskob put to Lamb may be the real explanation behind our fascination with these tall structures: man cannot resist the challenge of exceeding boundaries.
The introduction of steel into building construction in the late 19th century paved the way for tall, taller, and tallest. Steel production was cheap and made structures more fireproof, with steel columns and beams far superior to heavy bricks and mortar for support…especially for designs over six stories high. Elevators evolved to make it far easier – and safer – to travel up and down tall structures. Concrete matched the durability and versatility of steel. Now that the steel skeleton supported the load and not the outer skin of the building, glass took on a more important role. It was weatherproof, allowed in natural light and was much lighter and cheaper than masonry or concrete.
What’s next for modern skyscrapers?
The Empire State Building was considered the tallest skyscraper in the world from 1931 until the higher of the “Twin Towers” (1 World Trade Center) at 1,368 ft.) surpassed it in 1972. Because of the heights we are achieving today, the term “skyscraper” has been joined by two new terms: supertalls and megatalls.
- Skyscrapers: At least 164 ft. (100m) high
- Supertalls: Over 984 ft. (300 m) high
- Megatalls: Over 1,969 ft. (600m) high
Between 1930 and 1995, supertalls were rare birds and only numbered 15. Since then, on average, one supertall has been completed annually. That figure is now moving into double-digit territory and continues to rise. It is projected that the number of megatalls - like Dubai’s Burj Khalifa, which rises 2,717 ft. (828 m), will reach the number of supertalls completed in the 90s. The majority of these supertalls and megatalls are in China, Southeast Asia and the Middle East. The US, at one time the home of the tall building, only has one supertall in the top 10 list of completed buildings: One World Trade Center) at 1,776 ft. ( 541 m). Five buildings scheduled for completion within the next five years will reach or surpass 1,864 ft. (568m), with the Jeddah or Kingdom Tower in Saudi Arabia the tallest at 3,281 ft. (1000m).
The risks of skyscrapers
Reaching these incredible heights has its issues. Considerations include: the efficiency and speed of elevators, safety measures and sprinkler systems; wind loads and fire; the delivery and distribution of concrete; the ability to crane and lift loads at extreme heights; and the effects of seismic and natural catastrophes. There are also increased insurance risks when a project employs as many as 10,000 workers and over 100 subcontractors. The Chicago-based firm of Adrian Smith + Gordon Gill Architecture (designers of the Kingdom Tower) makes this observation: “There will always be people who will want to go higher. We are reaching a point, however, where it is economically unfeasible, despite being technically possible.”
As a provider of mobile offices, trailers and storage containers to the construction industry for well over 50 years, we at WillScot are intrigued and amazed by these super structures. How high in the sky can we go? Only time, economics, and man’s ingenuity will tell.