Why A Mile-High Skyscraper Is Almost Impossible | The Limit
This video explores the incredible engineering challenges and human ingenuity behind the world's tallest skyscrapers, questioning how high we can truly build. It delves into structural innovations, wind engineering, and the often-overlooked limitations of construction logistics and elevator technology. Ultimately, it reveals that the real limits to building a mile-high tower are less about technical feasibility and more about financial resources, political will, and human ambition.
1. The Sky's the Limit: Pushing the Boundaries of Height
The video kicks off by asking a fundamental question: "How tall can this really go?" 🤔 It highlights the relentless human ambition to build ever higher, starting with the historical record of the world's tallest buildings. For decades, structures grew incrementally, but the Burj Khalifa in Dubai dramatically changed the game, becoming twice as tall as the Empire State Building at a staggering 828 meters. Looking ahead, Saudi Arabia's upcoming Jeddah Tower aims to be three times as tall! Frank Lloyd Wright even envisioned a mile-high tower back in the 1950s, suggesting it was technically possible. The experts interviewed for this video agree that the Jeddah Tower isn't the ultimate limit, as "The sky's the limit." The journey to understand this limit takes us into the "hidden parts of the world's super talls" to explore the practicalities, costs, and ultimate value of reaching for the heavens. As the video intriguingly puts it:
"The higher the build, the stranger things get."
2. Buttressed Core: A New Era of Super Tall Structures
When it comes to building skyscrapers, there isn't just one right way to do it. From the classic steel frame of the Empire State Building to the modern outrigger systems in One World Trade, structural engineers see these systems as "different species, different animals" that operate at varying scales. However, a significant breakthrough came with the Burj Khalifa. Before it, most tall buildings relied on a single, central support structure, sometimes enhanced with "outriggers" to connect outer walls to the core.
The Burj Khalifa introduced a revolutionary "three-part design" or buttressed core, which ushered in a "new era of super tall structures." This innovative system, described as a "new species" and a "new animal," allowed the Burj Khalifa to shatter previous height records. It was over 60% taller than any building before it, a massive leap rather than an incremental gain. This tripod-like form is incredibly efficient:
"So, think of it as a three-legged stool. When you have four on a on a stool, if one's kind of a little off, you kind of feel it rock, but three is very efficient."
Surprisingly, this design also reduces the need for materials, with the Burj Khalifa actually containing less steel than the Empire State Building!
3. The Burj Khalifa Experience and "Vanity Height"
What's it actually like at the top of the world's tallest building? A producer's experience at the Burj Khalifa is described as "humongous" and "gigantic," with the structure dominating all surrounding skyscrapers. Getting to the top is an endurance test, involving a trek through the massive Dubai Mall and potentially a $500 VIP ticket for the full experience. The producer's awe-filled declaration, "I can see the infinity from here. Our producer may have enjoyed his trip," highlights the sheer scale.
This impressive feat of engineering raises a crucial question: Are these structures just "expensive tourist traps"? The numbers suggest they can be lucrative. The Burj Khalifa reportedly rakes in as much as $700 million a year from over 9 million visitors, making back its $1.5 billion construction costs in just three years from tourism revenue alone. It seems "it could be worth it to build tall just to stick a gift shop on top."
While the buttressed core has allowed us to build higher than ever, and a similar design is being used for the Jeddah Tower, it might not be suitable for a mile-high skyscraper. There's a "limit to how high this structural system is appropriate," perhaps around 1 to 1.2 kilometers. Beyond that, a "new species, a new animal, a new structural system" will be needed. Later in the video, we'll see a design for a structure ten times the height of the Eiffel Tower that looks nothing like the Burj or Jeddah Tower, overcoming these current height limits.
4. Confusing the Wind: The Ultimate Challenge for Super Talls
One of the biggest adversaries for super tall buildings is the wind. The video takes us to a meticulously calibrated wind tunnel at SOM (Skidmore, Owings & Merrill), where engineers use "good German very expensive styrofoam" models and even LEGO bricks to simulate wind effects accurately.
The main challenge comes from phenomena called vortices. When wind hits a round shape, it creates a "vacuum" on the other side, and as "wind vortexes come through each side alternately, they create kind of like a mini tornado that pulls on the building." This can be incredibly dangerous, especially if the building starts to sway at its own natural frequency. The classic example is the Tacoma Narrows Bridge, "Galloping Gertie," which collapsed due to resonance with wind speed.
The primary strategy for super tall buildings? "Confuse the wind." Engineers aim to disturb the organized vortices that could "wreck the building from side to side." This involves using "texture or form to confuse the wind." Sometimes, they even design buildings to "accept the wind," bringing it "through the body of the building" or utilizing "jump floors" – empty floors, like those in 432 Park, that allow wind to pass through and reduce shear forces. These empty floors also, ironically, make the upper occupied floors even more expensive.
Wind tunnel testing can lead to dramatic design changes. The Burj Khalifa's spiral was originally clockwise but was reversed to counterclockwise after wind tunnel results showed "the forces were too large, the motions were too large." This necessary change ultimately allowed the building to increase its height by 300 meters – the height of the Eiffel Tower!
5. Tuned Mass Dampers: Keeping Occupants Comfortable
Beyond structural design, modern skyscrapers employ a hidden trick to combat wind: tuned mass dampers (TMDs). These are "super heavy objects tuned precisely like a musical instrument," acting as giant pendulums that offset wind forces. Their main purpose isn't to prevent collapse, but to ensure the "comfort of people who are going to be living and working at the highest floors," preventing them from feeling the sway.
Every TMD is unique, calculated precisely for the building's size and structure. Examples include the beautiful spherical damper in Taipei 101, which is a sculptural element, and the electromagnet-controlled damper in Shanghai. Visiting the 500-ton TMD at One Vanderbilt in New York City, the speaker learns it's designed to withstand "110 mph wind hurricane actually hitting Manhattan." The engineer confidently states:
"I don't I don't think that building twice as tall as this is going to be an issue in the next 10 years. You heard it here first. Assume assuming somebody wants to pay for it and actually has a use for a building that tall."
Interestingly, the Burj Khalifa doesn't need a TMD because its buttressed core design with concrete at higher floors and its wind-confusing shape make it inherently stable. However, a mile-high skyscraper would likely need one, "or maybe more than one depending on how high up it goes." These mitigation measures, crucial for occupant comfort, can become "very, very expensive."
6. The Definition of "Building" and Uninhabited Structures
Sometimes, height is achieved through "vanity height" – uninhabited sections that add to the structure's overall stature. The Chrysler Building famously used a secret spire to claim the world's tallest title temporarily. On the Burj Khalifa, the spire alone is 244 meters tall, accounting for 30% of the structure, and is only accessible to technicians and a "few lucky celebrities." This spire itself would be the 11th tallest building in Europe!
This leads to a fascinating thought: if we're only trying to go as tall as possible, "why not just build one giant uninhabited spire?" If we "broaden the definition of the world's tallest building to the world's tallest human-made structure," the landscape changes dramatically. 45 out of the top 50 tallest structures are not buildings at all, but masts and towers, often radio towers.
The video takes us on a road trip to see a 400-meter-tall radio tower, taller than the Empire State Building but still not among the world's tallest masts. The tallest ever was the Warsaw radio mast, built in 1974, which stood at an incredible height until its catastrophic collapse in 1991 due to a guideline disconnection and gust of wind. These towers are "built for maximum height with the smallest footprint possible" and rely on fragile "guidelines" for support.
"If one of them fails, it could be catastrophic."
Antennas like these rarely exceed 2,000 feet due to aircraft risk, but could easily surpass the Burj Khalifa for a fraction of the cost and materials. Engineer Bill Baker, behind the Burj Khalifa, believes an uninhabited structure could easily reach 3,000 meters – almost two miles high! His design, a reboot of the Eiffel Tower, looks more like a broadcast mast, essentially hollow to let the wind pass through, making it highly stable.
This brings us to the "third rail" of skyscraper definition, as Daniel Safarik from the Council on Tall Buildings and Urban Habitat explains. They set the rules: antennas don't count towards a building's ultimate height. There are three criteria:
- Height to tip: The absolute tallest point, but unreliable as technology changes. The Willis Tower (formerly Sears Tower) is a prime example, with its antennas having varied heights over the years.
- Architectural height: The height to the top of architecturally integrated spires. This is the most common and accepted measure.
- Highest occupied floor: The highest floor regularly occupied by people.
For a structure to be considered a building, at least half its floors must be occupiable. So, a mile-high building could have 800 meters of habitable space topped with an almost equally tall spire.
7. The Rigors of Construction: Foundations, Materials, and Precision
Designing a mile-high building is just the beginning; the actual construction presents a host of "niche problems" that become "real sticking points" at such extreme scales.
Foundations
A strong foundation is paramount. It's not just about digging deep but finding the right location. Cities, often in river valleys or near ports, frequently have "terrible soil," making foundation work complex. The Petronas Towers hold the record for the deepest skyscraper foundations, requiring 104 concrete piles stretching 114 meters deep, meaning 25% of the structure's height is underground.
Materials
The strength of concrete has been a major limiting factor, but innovations since the 1950s have dramatically improved it, making it "almost 10 20 30 times stronger." This includes "super plasticizers" that reduce water content, leading to "ultra high performance concrete" theoretically capable of supporting a mile-high structure if thick enough. For the Burj Khalifa, extremely high-pressure pumps were needed to get concrete to extreme heights. Due to desert heat, concrete could only be pumped at night and required ice chips to prevent premature setting.
Logistics and Margin for Error
Building super tall demands meticulous planning and coordination. For the kilometer-high Jeddah Tower, "the logistics or strategy around getting that concrete up to over a kilometer...needs to be extremely well coordinated." Errors are exponentially magnified:
"We often kind of embed in our guys that, you know, on these projects when you make an error, you can multiply that error by a thousand times across the scale of this building."
Retrofitting an already built skyscraper is immensely expensive, as evidenced by the billion-dollar modernization of the Empire State Building. Furthermore, skyscrapers are typically designed to last only about a century, yet the average age for demolition of 200-meter buildings is a "pathetic" 41 years. This raises questions about the long-term future and maintenance costs of structures like the Burj Khalifa. Therefore, firms like Gil's ensure they use "best-in-class vendors for everything on their upcoming project."
8. The Elevator Challenge: The True Limiter for Super Talls
While structural issues might seem like the biggest hurdle, it's actually elevator technology that often lags behind in the race for height. In an 800-meter-tall building, stairs are not an option, making elevators the "most important technology."
The traditional problem lies with the sheer weight of steel elevator ropes. In a 500-meter shaft, there can be 27,000 kg of rope, and beyond that, the elevator simply cannot support its own weight and the rope. The current solution involves "multiple elevators and sky lobbies," where passengers switch cars to reach higher floors. However, this consumes vast amounts of valuable space and would be frustrating for residents of a mile-high building needing to change elevators two or more times.
A promising innovation is Ultra Rope, a carbon fiber elevator rope that will be used in the Jeddah Tower, allowing elevators to reach a kilometer high. But for a mile-high structure, even newer technologies will be needed. Frank Lloyd Wright's 1950s design for The Illinois, a 528-story tower, featured outlandish "76 five-story high elevators that could travel a mile per minute and be atomic powered," running on vertical rails like trains.
Once the "elevator challenge gets solved, designs can veer into the fantastical." Concepts like the X-Seed 4000 (4 km tall, housing a million people) and the Tokyo Tower of Babel (10 km tall, housing nearly the entire population of Tokyo) have been proposed. While some, like the X-Seed, were never meant to be built, they illustrate what's possible in theory. The true "limit is going to be set by... time as much as any time and political will and and financial resources." The Tower of Babel's estimated cost of three quadrillion yen ($22 trillion) highlights this perfectly – "basically a madeup amount of money."
9. The Ultimate Limit: Economics and Ambition
Ultimately, "more than wind, materials, and technology, it turns out that the real limit will always boil down to the bottom line." The world's top three tallest buildings average $2.6 million per vertical meter. While there are many practical reasons not to build extremely tall, and developers can profit from regular-height buildings, these super tall projects are often about much more than economics.
They are about "putting your city on the world stage." Like the Eiffel Tower, which is a "placemaker" that tells the world, "we're here," tall buildings serve as powerful symbols:
"If you're in a country or a city which has a lot of ambition and you're highly optimistic, a a distinctive good tall building is one way to to do it, you know, to to kind of plant your flag."
The speaker admits to initial skepticism about buildings getting much taller, but after speaking with the builders themselves, concludes:
"The question of a mile high tower isn't if, it's a matter of when."
The final question posed to the viewer is, "how much would you be willing to pay to buy a ticket to go to the top?"
Conclusion
This video masterfully demonstrates that while building a mile-high skyscraper presents immense engineering hurdles – from innovating structural systems and confusing the wind to developing advanced elevator technologies and ensuring robust foundations – these technical challenges are increasingly surmountable. The ultimate constraints aren't purely physical or technological, but rather economic, political, and a reflection of human ambition. Super tall buildings are often vanity projects that serve as iconic symbols, placing cities and nations on the global stage, making the pursuit of extreme height a perpetual quest of "when," not "if."
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