All language subtitles for How.Did.They.Build.That.S01E06.Arches.and.Opera.Houses.1080p.WEB-DL.DDP2.0.H.264-squalor_track3_[eng]

Narrator: How did
Dutch engineers

build a giant arch
full of apartments

on top of a swamp?

Woman: This one had
three stories' worth of mud,

to the point where the workers
actually had to wear wetsuits.

Narrator: What happened
when a rock-shaped opera house

was built using the most
modern and ancient techniques?

Woman: Anyone can build
a symmetrical auditorium.

But here they went
weird and wobbly

to build something exceptional.

Narrator: And how was
a piece of British history

re-engineered for
the 21st century?

Woman: That is 315 tons of
glass and 478 tons of steel.

Narrator: This is the
age of the extraordinary...

Man: This house always is
on the verge of falling down.

Narrator: Where
ingenious engineers

have unleashed
unchecked creativity...

Woman: Everything
in this building

pushes at the boundaries
of what's possible.

Narrator: Building
structures so outrageous,

they defy logic.

Woman: The forces on this thing

look like it should
be torn apart.

Narrator: Now their
secrets are revealed.

Discover the incredible
stories of their construction...

Woman: These are
extraordinary feats of engineering.

Narrator: To try and understand

how did they build that?

Rotterdam in the Netherlands

is one of the biggest
ports in the world.

Criss-crossed with
canals, rivers, and docks,

water is the
lifeblood of this city.

However, if you're a builder,
this water is much less welcome

and something for which
you'd better have a plan.

So when the city wanted to build

a massive new
horseshoe-shaped structure,

with four floors of
underground parking,

right by the docks,

Dutch engineers had to
use all the tricks in the book

to make it possible.

Corina kwami: This
building not only has

the visible engineering marvel
of a huge unsupported arch,

but equally impressive is that
they built this into a swamp.

Narrator: Specialist builders
had to dive deep down

in a muddy lake to
build foundations.

Clever concreters created an
incredible 12-story-high arch,

which engineers crowned
with extraordinary apartments,

apparently built on thin air.

These penthouses cover
dozens of buzzing market stalls,

restaurants, and shops.

And at each end are the largest
cable net windows in Europe.

This is Rotterdam's
markthal, or market hall.

So how did they build it?

Following German
bombing in world war ii,

Rotterdam's flattened city
centre had been redeveloped,

but somehow it
had lost its soul.

Jacob Van rijs: Rotterdam
was planned after the war

in a very functional way,

where they separated living

and working and shopping.

Nathalie De vries:
And business-like.

Jacob: Exactly.
So they realized,

hey, maybe we should combine it,

because it's not that
great to separate.

Narrator: To liven things up,
the city challenged architects

to design a permanent
covered market

with hundreds of new
homes on either side.

Winy maas: So the
program demands

for two slabs of housing,

and somewhere in
between a market hall.

I said to them, yeah,
but that's boring.

So instead of having
this, with the two slabs,

and then a market
hall in between,

I said, why don't we
turn it up, upside down,

so that you have
slabs on either side,

and you have more
penthouses here,

and you have a big hall,

like a space where
you can breathe,

and where you can
monumentalize good food.

Narrator: The final
approved design

was an ingenious merging
of housing and markets,

where not a square
inch of space was wasted.

It would all be built on massive
four-story-deep foundations

the size of two football fields,

dug out of waterlogged ground,
and waterproofed with concrete.

On top, 228 apartments,
cast in concrete,

would be stacked
like huge bricks,

creating the arch walls with
a final top floor of penthouses

that lock it all together
and create the roof.

Cladding inside the
huge 111-foot high tunnel

would create the largest
work of art in the world.

Finally, at each
end, a grid of cables

that would support
hundreds of panes of glass,

protecting the market stalls and
cafeés inside from the weather.

Joshua macabuag: They've
made an entire building

in this arched form,

and they've managed to
dot apartments and rooms

throughout it.

It's a really interesting andúquite
fun piece of engineering.

Narrator: Building the markthal

would require exceptional
engineering skills,

right from the beginning.

The ground is so
waterlogged here,

anything built
below ground level

acts like a boat on water.

Maurice hermens: The basementúis
actually like a bath at home,

and you would take a bucket,

@and try to push the
empty bucket into the water,

you have to
apply a lot of force,

and if you push it really
down, and you let it go,

it will jump upwards,
and the piles,

they have to
prevent the basement

actually jumping upwards.

Narrator: To counter this
extraordinary upward force,

engineers had to rethink
the role of the foundations.

Rotterdam is
completely waterlogged

just 6 and a half feet
below the surface.

A four-story deep
basement car park

@the size of two football fields

creates vast water
pressure underneath it.

So long concrete foundation
piles would be built down

to grip into the soil below,

stopping the
structure from rising.

But there's also
pressure on the sides;

@to counter this, a huge
concrete grid would be built

to hold the walls back.

This extreme water pressure

and the sheer scale of
the building's footprint

meant these foundations would
be some of the most complex

ever built in the Netherlands.

Work began in 2009,
as the site was cleared

and a retaining wall was
created using a combination

of interlocking steel
sheets and tubes,

making a strong
waterproof perimeter.

Then, inside the perimeter,
the main foundation piles

were made by first
driving huge pipes

to a depth of 100 feet.

An impact hammer
slowly, but noisily,

pushed each pile
into the soft ground.

With over 2,000 piles needed,

it was a slow and disruptive
process for the locals.

Man: It takes about
2,500 concrete posts

to build the foundation,

and there was a lot
of noise, you know...

[Banging]

So they make a wall of, I think
it was about 200 containers,

to reduce the noise.

Cracks in the walls,
surrounding buildings,

it had a lot of troubles
before it got here.

Narrator: With the pipes
hammered the 100 feet down,

concrete was poured in,

giving the building
its strong, deep roots.

Once set, the tips of
these piles were revealed,

and a massive
concrete grid built on top.

This will perform a temporary
engineering function,

by bracing the retaining walls

against the huge
pressure from outside,

as the engineers dig
down a further 36 feet.

And this is when
building in the Netherlands

gets really difficult.

Maurice: As soon as you
dig like two meters deep,

in this location,
you will find water.

The whole basement, we're four
stories underneath ground level,

is like building
something underwater,

it's a kind of
underwater building.

Narrator: As the winter
of 2010 progressed,

the site became flooded,

but instead of being a disaster,
it was all part of the plan.

The huge grid, now underwater,

was supporting
the walls at the top.

But as they dug down,

the lower part of the walls,
which aren't supported,

could collapse.

This is where the
flood water comes in.

Maurice: The water
inside the basement,

it gives a kind of
counter-pressure,

actually it gives exactly
the same counter-pressure

as the pressure
from the outside.

Narrator: If the excavators
dug down without water inside,

pressure from outside
would have pushed

against the lower dam walls,

and eventually the sides
would have caved in.

The water stopped that,
but made for hard work.

For months, excavator
operators worked blind,

only computer screens
telling them where to dig.

Eventually, all 5.5 million
cubic feet of material...

The equivalent of 64
olympic swimming pools...

Had been excavated.

Now the engineers had to prepare
the bottom of the foundation pit

for waterproof concreting,

with 50 feet of muddy
water still in place.

It was time for a
very specialized team

to get involved.

Corina: They continued building,
but with builders in wetsuits.

This is the most unusual
but ingenious method

for building foundations.

Narrator: Highly skilled
construction divers swam down

to install steel at the
bottom of the lake.

The piles that formed
the foundations

needed reinforcing
steel attached.

This steel would knit
together all the piles

and the first layer of concrete.

Once this was set, it would
lock together with the grid above,

creating a super
strong waterproof box...

Rigid enough to resist the
water pressure from the sides.

Maurice: Construction workers

are putting that
reinforcement in place,

making the connections
between the underwater concrete

and the piles, and
doing all stuff like that.

They were specialized divers,

which could stay down
for a couple of hours,

and then had to come up
again, and be refreshed.

Narrator: Like the excavators,

the divers couldn't see
what they were doing.

Diver: We see very
little under the water,

a lot of our job
is done by feel,

so it's basically
touch and movement,

and generally we
have to navigate by,

it's a mental map in our mind

rather than using
points of reference.

Narrator: With the steel
reinforcement in position,

the next crucial step was to
pour the waterproofing concrete

so the site could be drained.

Extraordinarily,
this was achieved

by pouring wet
concrete into the water.

Hayley loren oakes: It
might seem surprising,

@but properly mixed concrete
can set just as quickly underwater

as it can on land, as
long as it's poured gently

and it's not agitated
during setting.

And that's because it's
nothing to do with drying;

it's actually a
chemical reaction

that naturally expels water.

Narrator: For 72
continuous hours,

1,500 loads of waterproof
concrete were delivered,

laying down a 5-foot-thick layer

to seal the floor of
the foundation tank.

Maurice: After
the concrete is set,

you can pump out the water,

then you have your
empty building pit.

Narrator: It took two weeks

to pump out the 3.6
million gallons of water.

Then, the four layers of
car park floors were poured,

and the massively strong
3-dimensional foundation grid

was complete.

Now the 12-story
markthal could be built.

Right at the start, the
architects had the vision

that a roof for the
market would be provided

by building a huge arch...

An idea that won approval
from the structural engineers.

Joshua: Arches are a
very efficient structure.

They span a gap,

and they convert whatever
load is on that arch

into pure compression
within the arch

and take it down to the ground.

Maurice: The romans
were already using that.

They made concrete and brick
arches for Bridges and domes.

When it's there, it
really works well,

the trick is how to make it.

Narrator: Building an arch
means creating a curved shape,

which is good for strength,

but bad when 228 apartments

have to fit neatly
inside the arch itself.

To start with, the engineers
took a conventional approach.

Maurice: In Holland, the
construction technique

used for apartment buildings

is often something called

a tunnel-form
construction technique.

It's a set of walls and floors,

in which you can
pour the concrete,

and thus realize the
walls and floors in one go.

Ellie cosgrave:
Tunnel shuttering uses

these large boxes
that act as molds,

what we call formwork.

And these molds, you
pour the concrete around,

and once the concrete is set,

you can just slide
these molds out,

and use them again
in another room.

So this means that
we're saving time,

we're saving money

not having to create new
pieces of formwork every time.

Narrator: To speed
things up even more,

the engineers use
technology to keep tabs

on exactly when they
could move the build forward.

Maurice: There is
a system monitoring

the setting of the concrete,

and you can read out
the results through Wi-Fi

or mobile network,

so the contractor could see
the setting of the concrete

from his office

and know when he could take
the next steps in the construction.

Narrator: This technology,

and the repeated shapes
of tunnel-form construction,

allowed the floors to
be built up very quickly.

But how did the engineers
make the arch walls curve out

and then in as they went up?

Maurice: We thought
of using the apartments

as kind of bricks in the arch.

Putting the bricks every step,
putting the bricks a bit closer,

closes they gap
already for a large part.

Narrator: The structural effect

of this stepped
stacking of apartments

is especially plain to see

for residents who live higher
up in the curve of the arch.

Woman: Yeah, you
cannot hang stuff

in particular maybe
on these things.

You always have
to kind of find a way,

so shelves are not
really working that well,

but pictures still do.

Narrator: By mid-2013, with
the sides of the arch complete,

the last apartments to be built

would be the
exclusive penthouses,

forming the flattest
part of the arch,

and the roof of
the covered market.

Up until now, the build had
relied on the apartment below

supporting the one on top.

But in order to create the
arch, engineers had to figure out

how to support these
penthouses while they built them...

120 feet in the air

and over the whole
390-foot length of the hall.

Maurice: Filling
this whole space

with a temporary structure,

would be a project on its own.

It would be very costly,
it would take a lot of time,

so that was, that was the
reason to try to eliminate it.

So the whole temporary
support structure

was put on wheels on a crane.

Ellie: This structure is
essentially a reinforced tower

set on some tracks.

This means that as the
roof sections are poured

and allowed to set,

we can move the
structure along the building.

Narrator: One at a time,
the floors were craned in,

and then concrete poured

to build up the
penthouse structures.

When complete, they made up
the most crucial engineering blocks

in the entire building.

Maurice: If you have
an old-fashioned arch,

you will have bricks coming up,

and then in the end you
have a kind of closing stone

filling that gap.

The penthouses are actually
that kind of closing stone.

Narrator: Today, the residents
of these roof-section penthouses

enjoy peerless city views

and can literally look
down on their neighbours.

Woman: It's very special

because you see all
the shops downstairs,

and you can see the people
around you, so, yeah, it's nice.

Hi there.

You see, he likes it.

Narrator: By early 2014,

the project had
reached its final stage.

Cladding smoothed
the outside walls,

and the 4,000 aluminum
panels inside were each printed

with part of a giant mural.

The "horn of plenty" was created
by Dutch artist arno coenen

and at 118,000 square feet,

lays claim to being the
largest artwork in the world.

All that was left to complete

was to weatherproof it with a
wall of windows at each end.

The designers were determined

to retain the openness
of an outdoor market

and keep the incredible
artwork on show from outside.

The problem was,
Rotterdam's windy weather

meant traditional
windows this big

would need thick
frames to remain rigid

and prevent the
glass from shattering.

So the engineers found
another, more flexible way.

Winy: So, it has to be
closed, and, so no columns,

how can I do that?

I said, well, you
can make cables.

Narrator: An array of windows,
supported by a grid of cables,

is called a cable net facçade.

At 6,800 square feet each,

the ones they built here
are the biggest in Europe.

Hayley: The principle
of a cable net facçade

is very similar to
a tennis racquet,

where you have steel
cables that are like strings,

and then you have glass
mounted between them,

and this gives the strength
but also the flexibility

that's needed for covering
an area of this size.

Narrator: Like the strings
on a tennis racquet,

the cables in the facçade
must be extremely tight to work.

With the 48 cables in place,
they were then stretched tight,

so they could withstand
pressure from the wind.

Each 1-inch thick cable was
pretensioned by around 30 tons,

causing it to lengthen
by up to 6 inches.

Then, specialized
joints were mounted

onto the cable intersections.

Here the glass was
clamped on at the corners.

These joints, the cables,

and the silicone
between the glass panels

allow for an extraordinary
amount of flex

in this giant window.

Winy: I'm aware, it was
quite a work for the engineers,

to make the joint, because
when there is a storm,

say wind force 11
or something like that,

then it goes in, and out,
for more than a meter.

Narrator: In December 2014,

markthal's doors were
finally open to the public.

And they've kept on
coming ever since,

at a rate of around
20,000 people every day.

Jacob: It's now five years old,

and the amount of visitors
keeps more or less steady,

around at 8 million,

which is actually more
than the Eiffel Tower,

I can tell you.

Narrator: By making
this multi-purpose

market hall possible,

its builders have helped start
something big in Rotterdam.

Man: It's a real piece of art
that they've put here together,

and we really like it.

Nathalie: It's an amazing
piece of construction work.

It's also an
amazing civic place,

because it's for everybody.

Narrator: It may have taken
five years to rise from the mud,

but markthal now stands
as rock-solid evidence

of how great
engineering and design

can be a powerful
force for change.

♪

75 miles northwest of Hong
Kong, in southern China,

the brand-new mega
city of Guangzhou

wanted to get noticed.

It decided the answer was
an incredible new building

that would draw the
attention of the world.

They turned to a
legendary architect

with a reputation for
designing the impossible.

Zaha hadid didn't disappoint...

Dreaming up one of the
most advanced buildings

in the world...

Building a gigantic steel frame

with techniques that
are millennia old...

Mimicking natural forms
with mathematical wizardry...

And redefining the traditional
shape of a concert hall

that has gone
unchallenged for decades.

Corina: Anyone can build
a symmetrical auditorium,

but here they went
weird and wobbly

@to build something exceptional.

Narrator: This radical design
is the Guangzhou opera house.

So how did they build it?

The city of Guangzhou is
a giant metropolitan centre,

home to 25 million people...

Over three times the
population of New York.

In 2002, the regional government
commissioned a new centrepiece

that would hold its own

amongst the city's
gleaming skyscrapers...

A $200 million opera house.

It was designed by
the late zaha hadid,

an architect whose visions

pushed the boundaries
of engineering.

She found her inspiration
just a stone's throw away,

on the banks of the Pearl river.

Simon yu was the
project architect

overseeing its construction.

Simon yu: We had this concept
of these two pebbles by the river,

almost like placed
on the riverbanks,

and with a sort of water
that sort of washes over it

or these pebbles which are
dragged along the riverbank.

Narrator: The inspiration
may have been simple,

but it meant creating

one of the most advanced
buildings in the world.

Corina: When you're
emulating a natural shape,

the first things that
go out of the window

are symmetry and repetition.

Narrator: The complex would
be made up of two auditoriums...

A smaller 400 seater,

and next door, the
larger opera house,

able to seat 1,800 people
in its acoustically perfect hall.

Both buildings would
be cloaked in a net

of 12,000 tons of
steel-framed triangles

joined together by 59 huge
specially designed connectors,

creating a strong enough frame

for the building's
exterior coat.

Each is then covered

in over 75,000 unique
hand-cut granite triangles,

completing the stunning vision
of two pebbles on a riverbank.

The engineers started
with the simple part...

Making the two
concrete structures

that would house
the concert halls.

These went up quickly using
tried and tested techniques.

The first major obstacle came

in the form of the
giant steel enclosure

that wraps the
cement structures...

A vital part in creating
the building's shape.

Nehemiah mabry: The Guangzhou
opera house is very clever,

because it feels like
something that's fluid, light,

very free flowing,

much like its
pebble inspiration.

But underneath its
curvy skin, it's packing

some very, very sophisticated
geometry and engineering.

Narrator: The answer to
building the extraordinary

140-foot-tall, 390-foot-wide,
pebble-shaped shell

lay in the humble triangle.

Nehemiah: Despite
competition from circles,

triangles are actually
the strongest shape.

They're able to
distribute a load evenly

throughout all three sides,

and so because of this,
here is really the best shape

for evenly
distributing the load,

carrying it all the way down
to the ground of the structure.

Narrator: To create
these triangles,

the engineers needed
to design and build

59 unique star-shaped
joints, called knuckles.

The incredibly complex design

relied on the power
of the computer.

But for manufacturing them,

they turned to an
ancient technique

called sand-casting.

Simon: The way they were made

was actually quite
old-fashioned.

It was very, very
simple in the sense

that they actually would
make a 1-to-1 version

of the steel members in wood.

Narrator: To create steel
joints using sand-casting,

the engineers first made
the exact shape out of wood.

In a foundry, this wooden shape

is sandwiched between
two layers of sand,

the wood is then removed,

leaving a perfect imprint
and creating the mold.

Then, molten steel is
poured in, it hardens,

and when the sand is removed,

a steel version of the
wooden shape is revealed.

Simon: These knuckles were
actually all absolutely unique,

and they have a
very, very tough job

of keeping and
bracing all these,

a lot of the steel
together, you know,

they all work together.

Narrator: All the
knuckles combine

to form the
super-strong outer shell.

Ellie: Sand casting, it sounds
like really old-fashioned,

right, but in this
instance, it really is a case

of if it ain't
broke, don't fix it.

The shang dynasty were
using this technique in 1300 bc,

and it's still in use today
to make one-off pieces.

Narrator: With
the frame in place,

the next challenge was
creating the pebble-like exterior.

The solution lay in
yet more triangles,

each individually cut to cover
the 12,000-ton steel frame.

It would be an
impressive effect,

but an engineering nightmare.

To mimic the natural shape
of a river-washed pebble,

every triangle had to be
cut to exact specifications

that changed constantly.

To make things even harder,

the clients loved the idea
of the pebbles so much,

they wanted the building clad in
super heavy, super hard granite.

Ellie: The total granite
facçade cladding area

is 24,700 meters squared,
with 75,422 separate pieces.

That is essentially the
Jigsaw puzzle from hell.

Narrator: The engineers
had all 75,000 pieces of stone

cut to size off site.

Every tile had a
tolerance of 5 millimetres,

and lasers were used to make
sure each was precisely placed.

With the outer shell complete,

the engineers turned their
laser sights on the sky lobby...

An area between
the concert halls

and the outer shell,

where the designers wanted
to create a futuristic space

with floating walkways
with no visible support.

The solution hidden inside
these impossible balconies

are a secret collection
of steel boxes,

anchored to the building's
sturdy concrete core,

that support the structures,

giving the illusion
of weightlessness.

They are covered with
white organic cladding,

created in huge
computer-designed molds

that were filled with
white gypsum plaster,

and anchored to the steel and
concrete frame, piece by piece.

Ellie: These two
separate structures,

this self-supporting outer ring

and the inner
concrete structures,

creates this space in the middle

that appears to be
completely unsupported,

and this allowed the
architects to play around

with these floating staircases,

and these cantilevered levels

that appear to
completely defy gravity.

Narrator: The real challenge

lay in creating the
concert hall itself,

to create perfect sound,

concert halls are traditionally
perfectly symmetrical.

This, however, is anything but.

The key lay in controlling

how the sound bounces
around inside the hall.

Hayley: The art of acoustics

is getting the
reverberation just right.

If there's too little a gap,

then everything
sounds quite flat,

but if there's too long a
gap, then you get echoes,

and it sounds quite muddy.

Narrator: They turned
to one of the world's

leading acoustic
engineers to pull it off.

Peter fearnside: Getting the
reflection sequences right...

That's the sound that hits
the wall or hits the ceiling

and ends up at the audience...

Is vitally important,

because it adds to the
strength of the sound.

It can add to the
clarity of the sound.

Narrator: The way you do that

is by building what's
called a shoebox shape.

The sound bounces off the
walls and back to the audience.

The problem is the
bigger the auditorium,

the further the audience
is from the stage

and the worse the view.

But if you fan the audience out,

the quality of
sound deteriorates.

With an 1,800-seat capacity,
this space would be huge.

So the team had to find a way

to keep the audience
close and the sound perfect.

Peter: One of the
alternatives is asymmetry,

where you can use the side
walls of the asymmetrical hall

to reflect the sound in a way
that is similar to a shoebox,

that you enforce
the lateral reflections.

Narrator: So the
plan was to create

curved walls and surfaces
within the auditorium,

to direct the sound exactly
where the engineers wanted.

But figuring out how to
do this was so complicated,

they decided to build
a model of the hall,

where the team
could test it out.

Peter: In the scale model,
you can't test at every seat,

but you use dummy heads and
microphones to test at a sample,

and also you test

where you think you potentially
are going to have a problem.

Narrator: By analyzing the sound
recorded on the tiny microphones

in the different positions,

the team was able
to build up a picture

of exactly how to shape
the inside of the hall.

Peter: What we were
looking for in the model

was strong, focused reflections,
from concave surfaces,

but also the presence
of multiple reflections

which will give you
the effect of an echo,

and such complex space,

that this was the only
way we felt at that stage

we could do it.

Narrator: By bending
and curving the walls,

the team was able to
create an amazing sound

and not compromise the view.

The result of all these
complex solutions

of engineering problems

is a building inspired by nature

that is truly out of this world.

Ellie: This building for
me is a perfect example

of what happens when
architects and engineers

and all sorts of other experts

work together to challenge
the ordinary and the simple.

Narrator: In the
heart of London,

engineers and architects
faced a problem...

How to help a
180-year-old building

find its place in
the modern world.

The solution was a
breathtaking revamp,

which meant demolishing
two acres of the old structure

and, using
mathematical precision,

replacing it with an 800-ton
roof of steel and glass.

This is the great court
of the British museum.

So how did they build it?

At the turn of the century,

the British museum was in
dire need of modernization.

The centre of the museum

was a cluster of small
and confusing rooms,

and with nearly 7
million visitors a year

struggling to see
its 50,000 items,

the time had come for change.

But transforming a building
that's almost 200 years old

is a very different proposition
from building one from scratch.

Corina: Working with an old
building can be a nightmare.

You never know
what you're gonna find

or what problems
you might run into.

Narrator: The man
tasked with the challenge

was one of the world's
leading architects,

responsible for the
millennium bridge

and the millau viaduct.

Lord foster: To get from
one gallery to another,

you would have to
plow through a gallery,

so it was a
constant traffic jam,

and it wasn't very pleasant.

Narrator: Lord foster's
solution to this maze

was to knock it down and
create an enormous open space

between the exterior facçades
and circular library in the middle.

Over that would go a
show-stopping glass roof

to create the largest
covered square in Europe.

Lord foster: If you then
imagine, kind of surgically,

you take all that stuff around
the great circular library,

and you've suddenly
got breathing space.

You've got a vast space.

How do you put
this glass umbrella

so it will evaporate, and
it's like an artificial sky?

Narrator: The plan?

To demolish the mass of rooms

filling the area outside
the central round library,

then, to reinforce
its foundations

before building a protective
shell around the reading room

and strengthening
the exterior walls.

Then it could receive
the 800-ton roof,

made up of almost
5,000 pieces of steel

and over 3,000 panes of glass.

No two would be the same.

In 1998, with the exhibits
moved into storage

and the books from
the reading room

moved to the British library,

work began on demolition

and shoring up the
180-year-old foundations.

Mike cook: At the time,
the great court project

was a complete rebuild
inside of the courtyard.

Narrator: Pulling this
off was full of risks.

They had to strengthen the
almost non-existent foundations

by pumping concrete two stories
underneath the reading room,

creating a reinforced
slab for it to sit on

and excavating a new
basement underneath.

Mike: The reading room is a
very early, delicate cast iron frame

with a very beautiful and
listed papier-maâcheé ceiling.

Papier-maâcheé's dry
and very, very delicate,

very prone to
cracking, so, as we dug,

you didn't want any movements,

or you could easily
have cracks appear.

Narrator: The library sat
on shallow foundations

that would never take
the weight of the roof,

so stage one was to underpin it

by pumping in thousands
of tons of concrete.

Even this was a
delicate operation.

Knowing the work could
disturb the structure above,

alarms were installed.

And it turns out,
for good reason.

Mike: I remember the
message coming back, you know,

oops, the alarms have gone off,

we seem to be lifting
the reading room,

we'd better stop,

and the pumping had
got a bit carried away

and started moving the
reading room upwards.

Joshua: Can you imagine
being the engineers at this point,

where you've got a precious
piece of English history

that's stood there
for hundreds of years,

and now it's at risk of being
quite seriously damaged.

Narrator: The next major
engineering challenge

was that the very delicate
central reading room

was nowhere near strong enough

to carry the weight
of the new roof.

Mike: In order to
keep the heavy weight

off the central reading room,

we didn't want to load the roof
onto the central reading room,

so we had put in
a ring of columns.

They had never got a proper
skin on the reading room.

It was very ordinary brick.

It was never designed to be
seen, so it needed a new skin.

What foster's cleverly
did was leave a little gap

between the new stone
and the existing brick,

and in that gap, we
put 20 new columns,

and a whole load
of cross-bracing

to stabilize those 20 columns.

And that gave us
a beautiful place

to take the weight of the roof,

and by putting the
cross-bracing in,

it also wasn't gonna
wobble sideways,

so it was a really stable core,

and nobody even
knows it's there.

It's all hidden
behind the stone.

Narrator: So with the
foundations in place,

the engineers were able to
build a hidden steel structure

around the central library

that would carry the
weight of the roof.

The library itself
would sit safely inside,

with the steel structure hidden
in the new external finish.

Finally, the old building
was ready to take the weight

of the new glass roof.

However, designing
a curved glass roof

that would join the
square outer walls

to the circular library

was a serious
mathematical headache.

Mike: I think you have
to go and see the roof

to kind of understand
why it's complicated.

Ellie: It looks floaty,
light, effortless,

but that is 315 tons of
glass and 478 tons of steel.

Narrator: The team needed
help to realize the design.

They turned to computer power.

Mike: At a time when we were

only just getting used to our
computers, you know, really,

in terms of defining
complicated geometries,

you know, now, 20
years on, it's pretty easy,

but it wasn't then.

Lord foster: The
computer, it enables you

to see the implication of
one or several variables,

making it possible
to create something

that is at one and the same time

extraordinarily complex,

but to make it look
incredibly simple

and, in the end, poetic.

Narrator: With the
geometry of each piece

of glass and steel calculated,

the engineers got
to work transferring it

from the computer
to the courtyard,

starting with building the
two acres of steel mesh.

Lord foster: So,
it's a new structure

at the circular heart of this,

and then all that very delicate
tracery of steel members,

11 kilometres in total length,

making over 3,000,
3,300 triangles,

and that whole thing can move,
it can expand, it can contract,

it can absorb snow
loads, it can move,

and it's only
delivering vertical loads

onto the historic fabric.

Narrator: The
team then installed

the 3,312 panels of glass.

With no two pieces the same,

it was an enormous
Jigsaw puzzle to complete.

Lord foster: It's
like an iceberg...

You are seeing the tip.

What you're not seeing is
that extraordinary body of work

by so many individuals,
the people who made it.

Narrator: Finally, on
December 6, 2000,

the great court
opened to the public.

Corina: It's the largest
covered public square in Europe,

an incredible piece
of engineering.

Narrator: The new courtyard
with its floating glass roof

is the result of
thousands of man-hours

from lord foster's team

of designers, builders,
and engineers.

The result is an
extraordinary modern structure

that has transformed

one of London's most
important buildings.