How Did They Build That - First Season

How does this incredible skyscraper

defy the laws of physics?

This house always is on the verge of falling down.

What happens when one of the world's richest men

and its most extreme architect

create the impossible?

Obviously we know that levitation of buildings

hasn't been invented yet.

And how do you build a 1,000-foot-high elevator

in an area so remote,

heavy machinery can't be used?

This is the age of the extraordinary...

Where else can you swim from one skyscraper to the other

300 feet in the air?

Where ingenious engineers

have unleashed unchecked creativity...

Everything in this building

pushes at the boundaries of what's possible.

Building structures so outrageous,

they defy logic.

The forces on this thing

look like it should be torn apart.

Now their secrets revealed.

Discovering the incredible stories of their construction...

These are extraordinary feats of engineering.

To try and understand

how did they build that?

New York's Manhattan island,

where the skyscraper rules the roost.

Ever since the first one went up over a century ago,

the drive has been to push towers taller and cheaper.

But the resulting demands on engineers

have created repetitive, predictable shapes.

Creative flair and groundbreaking design

were rare exceptions.

That was until 2017,

when in Manhattan's Tribeca district,

a spectacular new tower was unveiled.

This is 56 Leonard street,

where a team of engineers and architects

stepped over the cutting edge,

ripping up the skyscraper rule book.

The shapes are extraordinary...

Boxes stacked on one another.

And some of them are slid out.

The whole thing looks so precarious.

At Leonard street,

56 stories of unique apartments

are stacked ever more daringly right up to its 820-foot summit.

Here at the top,

engineering logic seems to have been recalibrated

to defy the laws of gravity.

It all just looks a bit scary.

Unique apartments with sky-high impossible overhangs

created a complex and expensive construction.

So, how did they build it?

Even more than most cities,

Manhattan is space-hungry,

resulting in tall buildings with simple layouts

that are a compromise between the engineering challenge

of building a skyscraper

and the practical economics of doing it at a price.

Most skyscrapers and tall buildings

are either rectangular or tubular

because those are really efficient shapes

when it comes to supporting themselves.

For construction purposes,

developers like to have buildings be fairly regular

and columns going straight down, et cetera,

so that every floor is the same

and they can just build it nice and quickly.

These uniform layouts are now so efficient to build

that a conventional high-rise with over 50 floors

can be completed in just weeks.

But the results are often a little underwhelming.

Imagine, you wanted to change things up a bit.

You could put this cantilevered section

in there...

This box section in there.

And you might want to even like take out bits...

Oops.

Changing it up

in the world of skyscraper construction

means taking risks.

But that wasn't going to stop developer izak senbahar.

We knew this was gonna be a very tall structure

and very visible from almost every angle in the city.

So we said, OK,

we have a responsibility to do something iconic.

We didn't want something repetitive,

some just straight up building.

We wanted something more interesting,

more sculptured.

When izak bought the site in 2008,

Tribeca was not one of Manhattan's

glamorous residential districts.

But building something special anywhere in New York

is expensive,

so these apartments would have to command top dollar.

Needing a design that would attract the uber rich,

izak headed to Europe

and world-renowned Swiss architects

herzog & De meuron.

We felt that izak was ready

for a new approach,

a more radical approach.

Herzog & De meuron's portfolio

includes some truly incredible buildings,

like bayern Munich's arena stadium

and London's Tate modern extension.

But no skyscrapers.

Even if we had done a building before,

a tall building,

we would always look at it from a different angle

and would give him something unexpected.

We want it to be a stack of apartments

but not an anonymous one.

The building could be understood as a pile of individual pieces,

even in the middle part,

and then the top,

which would have even more exclusive apartments

which we decided could become like stacked private homes.

And I think that's really new

and hadn't been done before anywhere.

There's good reason it's never been done before.

In order to make a strong, stable building,

irregular spaces are normally built

into the super stable lower floors,

with smaller structures at the top.

The architect concept that the higher the apartments are,

the more off-balance they appear,

flipped conventional high-rise engineering on its head.

To pull this trick off at the top,

they needed to reduce

structural complexity lower down,

while still making the floors appear to be different.

To do this, they hatched an ingenious plan.

The first 46 floors would be built in the conventional way,

using continuous outer columns and inner walls

to provide support for the floors above.

The floor layouts would also repeat,

but they'd be made to appear different

by changing the size and position of balconies and edges.

The 46th floor would be unoccupied

and so could be packed with load-bearing walls,

creating a 47th floor plate

that would be super-strong, super-stable platform.

Skyscraper specialist hezi mena

was the structural engineer tasked with making it happen.

We tried to stiffen up the building enough

up to the 46th floor.

So when we reach the 47th floor,

the first sky villa,

the building will have sufficient stiffness

that we can have the flexibility

of doing whatever we want structurally

and give the architect the freedom

to do whatever he wants with the space.

And what the architects wanted

was to create an extraordinary visual effect.

If you make this upper box,

let's say, hover to a certain degree,

you don't make it hover so it collapses.

You can push it to an extreme, you know,

like in chaplin's movie, you know,

where this house always is on the verge of falling down.

Together with the structural engineer,

you find the right moment between something fragile,

something even dangerous.

The vision for off-balance apartments

that still had wraparound views

meant pushing structural concrete engineering

right to the edge.

The lower floors

used conventional skyscraper engineering,

where continuous columns share the load.

But because the top nine floors are all offset,

that same system wouldn't work.

Each of these floors has to be stiff enough

to support huge cantilevered overhangs,

some over 23 feet.

And they had to do that

without compromising the view from within.

To pull it off,

engineers turned to a 125-year-old idea...

The vierendeel truss.

A regular truss uses diagonal cross members

to create triangles

that make it very strong both laterally and vertically.

But the views from within would be ruined.

A vierendeel truss

connects the two floors using only vertical columns.

So it's just as strong vertically

and it keeps its lateral strength

through the massively strong central lift shaft column

that also connects the floors.

So the vierendeel truss allows huge openings,

and the apartments above can be offset with crazy overhangs.

A vierendeel truss is actually a brilliant solution

for a long cantilever.