They look at the buildings over 1,500 feet, all with completion dates between 2004 and 2020, a very short 16-year period. They estimate that one 5000 foot building every 40 years.
The 1000 meter (3268 foot) Kingdom tower is budgeted to cost US$1.23 billion and is part of a $20 billion project.
The Freedom tower is $4 billion and will be 541 meters tall (1776 feet)
The planned 202 story Sky City is to be 838 meters tall with a roof at 727 meters and will cost about $1.5 billion. It would be 3 times cheaper than the Burj Khalifa per square foot and ten times cheaper than the Freedom Tower.
China's Broad Group has architectural plans for a two kilometers (1.25 miles) high building. When asked to estimate the odds of this 636-floor skyscraper ever being built, Zhang responds without hesitation, "One hundred percent! Some say that it's sensationalism to construct such a tall building. That's not so. Land shortages are already a grave problem. There's also the very serious transportation issue. We must bring cities together and stretch for the sky in order to save cities and save the Earth. We must eliminate most traffic, traffic that has no value! And we must reduce our dependency on roads and transportation."
The cost of a 636 floor super-SkyCity would be about the same or less than the Freedom Tower.
A lot of Spire
Technically a skyscraper can have up to 50% of its height with unoccupied spire. So if there was maximum spire then the 202 story Skycity could have 1450 meters of height if they had a 723 meter spire.
A maximum spire on the super-Skyscity could allow the 636 story building to have about 4 kilometers or 2.5 miles of height.
One third of the Freedom Tower is spire. Its roof is about 400 meters high.
So if a skyscraper developer is motivated to get the height record they can build quite a tall building but add as much spire as possible. This adds a lot less to the project cost while "technically achieving" some new height record.
I and many other have forecast that China will
1. Increase urbanization from 50% to 80% over the next 2-4 decades
2. This will increase the size of China's largest cities
3. I believe the Skycity will be built and that Broad group will prove out lower cost construction of megatall buildings
4. China's per capita income will go up to 5 times or more on a exchange rate basis over the next 2-4 decades
Many chinese cities will definitely be able to afford a Freedom Tower $4 billion project and that would be super-Skycity class building.
China could also afford a $20 billion Kingdom tower project and could put more of it into one building.
China could even afford a $100 billion building project especially as the SkyCity model lets mixed use to (farming, living, working, hospitals, fire department, schools etc...) to all be put into one building.
There have been advances with the length of elevators with a carbon fiber for the elevator cable.
Improved elevators (perhaps systems without cables that were magnetically based) would also be needed for radically taller skyscrapers.
A 5 mile tall skyscraper with 5 miles of spire could become achievable.
Unoccupied inflated space towers could also be developed for 100 mile tall structures for launching payloads into space. They are more buildable and practical than space elevators.
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