The supertall skyscraper is just a few years away from its one hundredth birthday – that’s
a pretty big deal.
In 1928 work began on the Chrysler Building, the first manmade structure to soar more than
300 metres into the sky and claim “supertall” status.
Since its construction more than 170 supertalls have risen across the world (source) – and
there are currently well over 100 more under construction.
Now, we are finally beginning to see how these massive structures will age.
It’s easy to forget when looking at such monoliths that buildings are not permanent
things.
Afterall how many 200 or 300 year old buildings do you know that are currently still standing,
and being occupied?
The list isn’t that long.
Skyscrapers, like every other building, have a shelf life.
And as we build more and more of these massive structures it’s worth asking how long that
shelf life actually is.
We already have some very tall, very old buildings that have stood for centuries.
The 111-metre St Paul’s Cathedral has dominated London’s skyline for 347 years and remains
intact and in use to this day.
And arguably one of the world’s first skyscrapers, the Great Pyramid of Giza - which has eroded
now to a height of 139-metres - has been standing for 4,500 years.
But could we ever expect a modern-day skyscraper to stand for millenia?
Is that even possible?
Well surprisingly, the answer is: maybe.
In order for a building to survive that long it has to battle two things: the limits of
its materials and the elements.
To understand how that works in practice we need to look at how some of our oldest and
tallest skyscrapers are being kept upright today.
Structurally, most of them are likely to be safe.
But we need to keep adapting them, keep using them flexibly in order to keep them.
To put it simply, they just don’t build them like they used to.
When the Empire State Building was being constructed back in the 1930s engineers were still calculating
everything by hand, so they overcompensated.
Extra steel was added, just in case – and as a result the 92-year-old building is incredibly
robust.
(source)
Compared to a modern day skyscraper like the Burj Khalifa, which is more than double the
height of the Empire State Building, the Empire State weighs more than twice as much.
In 1945 a small B-52 plane even crashed into the side of it and the building was reopened
in a matter of days.
(source)
But this robustness wasn’t a certainty.
Not having enough real life examples at the time, engineers feared the steel beams inside
the building would not last more than 60 years if nothing was done to preserve them.
(source)
Of course, the Empire State wasn’t left to just erode into dust and over its lifespan
it has undergone many different retrofits and operations to keep it upright.
Starting in 2009 a decade-long retrofit costing more than $120M gutted and replaced much of
the building’s internal pipes, gauges and heat exchange machines to make them more energy
efficient (source) – and more than $550M was spent renovating the observation deck
and public lobby areas (source).
Retrofits like these are important to keeping the building in line with modern standards,
but it's what the building is made of at its core that could really keep it standing for
centuries.
So the structure of a high rise building is typically built from concrete, reinforcing
steel, and structural steel as well.
These are the big materials that we use to build skyscrapers.
if I break that down by a kind of material and an example of concrete, for instance,
is the pantheon in Rome that's almost 2000 years old now, and that's the oldest concrete
structure in the world.
It's been there for hundreds of hundreds of years, and there's no reason why we couldn't
have that in our skyscrapers these days.
The skyscraper’s steel skeleton is remarkably resistant.
In fact, nearly all modern skyscrapers are made up of steel beams.
These beams have a shelf life of about 100 years before needing to be replaced – and
it’s actually quite common for steel beams to be replaced piece by piece in old skyscrapers,
especially in New York.
As long as they are continually replaced, theoretically there is nothing stopping a
building like the Empire State from lasting for centuries.
Some engineers have argued that as long as there remain people to upgrade and improve
these buildings, skyscrapers could outlast the pyramids.
So when a skyscraper is in its planning stages, we we absolutely talk about the design life
of that building, how long it's built, what it's going to be used for in 50 years time,
in 100 years time and beyond.
And the crux of the matter is that that the structure of a high rise building is essentially
indefinite.
So if the materials are sturdy and easily repaired or replaced that just leaves one
enemy for the skyscraper to contend with: the elements.
Modern-day supertall skyscrapers now have the benefit of a hundred years of engineering
developments and breakthroughs.
The Burj Khalifa has been designed to withstand hurricane level winds that are predicted to
occur just once every two thousand years in the region.
It’s the building’s sleek aerodynamic design that tricks the wind.
Its steeped form reduces in size and tops out unevenly around a central spire.
This deflects the air currents and prevents them from forming vortices that would shake
the tower from side to side.
(source)
Many tall buildings around the world employ this technique.
The Shard uses jagged edges, the Willis Tower has a steeped profile, and the Petronas Towers
taper to their summits..
These modern day structures are built to withstand centuries of battering by high winds, rain,
earthquakes, and whatever else mother nature might hurl at them.
Earthquakes are extremely rare events and extreme earthquakes are even rarer than the
usual earthquakes that we're used to feeling.
So we might design a building for an earthquake in one in every two and a half thousand years,
for instance.
And what's quite interesting now is that as we see the effects of climate change, as we
see more storms, as we see higher winds, that we're able to transfer this performance based
approach from seismic design into these extreme weather events that we're starting to see.
But not every skyscraper is the Burj Khalifa or the Empire State.
Rapid urbanisation around the world has created a second tier of skyscraper – one that won't
be city-defining or icon-creating, but that’s built purely to be functional and very, very
tall.
These buildings don’t seem to have longevity in mind.
They’re built as quickly as possible for as many people as possible.
So what happens to these buildings and how long will they last?
To find out we have to travel to the Chinese city of Shenzhen.
It’s exploded from a little known fishing village with fewer than 30,000 people in the
1980s to a megacity that’s now home to 12M.
This hub of innovation and ideas has become dubbed the country’s Silicon Valley - and
it’s probably where your mobile phone was made.
To accommodate such growth a massive construction blitz had to be undertaken.
But that meant that some buildings were constructed quickly to meet the immediate needs of the
city without future-proofing in mind.
Shenzhen is now left with some massive concrete structures that are nearing the end of their
relatively short lifespans and there’s only two options left: demolition or regeneration.
This 100-metre high concrete tower has opted for regeneration and perhaps provides a blueprint
for how these buildings will be dealt with in the future.
“it is surprisingly recent as it was completed in 1994 and came into use in 2002.
So it is really emblematic of the first period of shenzhen's explosive growth, let's say.”
“So when we first visited it about a couple of years ago, we saw an edifice which was
either partially abandoned or in, in heavy stages of decay”
This is what the office building looked like, and this is what it will soon become: the
Shenzhen Women and Children’s Centre.
“The building I think is representative of the of the time when it was built…”
“So it was in this very first rapid, spur, rapid growth of the city.
And so I don't think.
Possibly at that moment, enough attention was paid, you know, to the needs of a building
that needs to serve women and children specifically, and the public at large.”
Instead of a costly and wasteful demolition process, the building’s core will be preserved
and reused, finding new life and a new purpose.
“Retaining and refurbishing a building is more sustainable than demolishing it and building
anew.”
: “We are happy to be part of such a process, which is so different from what usually happens
in China.
We were able to salvage 80% of the original concrete structure, which amounts to approximately
24,000 cubic metres,
As Shenzhen continues to expand there isn’t room for these old buildings to sit there
and become disused.
Space is valuable, and many in the city are looking to this project as a case study.
“We will see for sure more large scale retrofitting of highrises in the future.
It is inevitable that many of the high rises that were quickly built over the past 30,
40 years around the world and particularly in China, will need a refurbishment over the
next ten, 20 years,So replacing all of them with newer buildings will not always an option
and in most cases will not be a sensible and sustainable option.
So I think we need to think in different terms about existing contemporary architecture as
less disposable and more recyclable.”
Skyscrapers are ultimately highly functional buildings.
They create huge amounts of space on small, urban sites.
We build them to house us, shelter us and give us a place of work.
Every skyscraper in the world has a purpose and we’ll continue repairing and maintaining
them as long as that remains true.
So if the infrastructure is properly maintained, properly inspected and properly surveyed.
There's no reason why the structure of a building couldn't last for many hundreds of years.
So what's really interesting is that in the past 12 years, we've built more skyscrapers
than the rest of human history combined.
So we have a huge stock of tall buildings that are being used well today.
But they need to be adapted and they need to be retrofitted, extended and changed over
time so that we can keep them, use them flexibly and maintain their long life.
Will we ever see a 500-year-old skyscraper?
Well probably, yes.
These buildings will continue standing as long as we need them to.
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