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00:03Notre Dame de Paris, a treasured icon of gothic architecture and medieval construction.
00:10But on April the 15th, 2019, disaster strikes.
00:16A devastating fire rips through the cathedral, threatening to bring down the entire structure.
00:25For the second time, I've been given the most marvellous opportunity to visit the worksite here at Notre Dame,
00:33where a huge team of people are working away on the cathedral.
00:37They've rebuilt the walls, they've restored the interior, and now they're nearly at the end of their five-year adventure.
00:46I can't wait to see what's been happening inside.
00:53We'll meet the master craftspeople and engineers battling to bring Notre Dame back to life.
00:59There are five or six hundred people here every day. It's a huge adventure.
01:06Hundreds of workers are entering the final critical stage of an ambitious race to restore this medieval masterpiece,
01:13in time for a grand reopening.
01:17It's a gigantic puzzle, like no other.
01:21Historians and scientists work together to analyse and reproduce Notre Dame's architectural mysteries.
01:29This piece with this piece are together.
01:32They're revealing ancient technology, hidden for centuries.
01:36This mark is almost on every piece of wood in the carpentry.
01:40And battling to save the fragile structure of the building.
01:44Now in the final stage of this extraordinary five-year restoration project.
01:50This is the inside story of the race to save Notre Dame Cathedral.
02:05Paris, the city of lights.
02:11A destination for millions of visitors from around the world every year.
02:19On April the 15th, 2019, the 850-year-old cathedral of Notre Dame de Paris was undergoing an £8 million
02:28renovation of the spire
02:30when a fire broke out inside the oak framework of the roof.
02:35After 90 minutes, the 800-ton timber and lead spire gave way.
02:41It crashed through the stone vaulting below, creating gaping holes.
02:51Now, this old lady is looking very different from when I was last here.
02:57OK, there is still scaffolding.
02:59But look, there's a roof up there.
03:01And the spire is back.
03:04There it is, shooting up towards the sky.
03:08If you squint your eyes and pretend the scaffolding's not there,
03:12it's almost like that fire never happened.
03:17Back in 2019, the focus was to protect what had survived
03:21and begin the task of rebuilding the cathedral.
03:25Workers removed 40,000 burned and melted scaffolding poles
03:30left over from the spire restoration
03:32and erected a temporary roof that opened and closed on special rollers
03:37to keep the stonework and interior dry.
03:41During all this work, the medieval masterpiece has been closed
03:45used to worshippers and tourists alike.
03:50Around 13 million people toured Notre Dame each year before the fire.
03:56They came to marvel at a building that pushed the limits of Gothic architecture.
04:01Tragic as the fire was, I think it took something like that
04:07to make us understand just what an absolutely amazing work
04:13of collaborative genius that building was.
04:20It's still not known how the fire started, but five years later,
04:25the ambitious project to restore the cathedral is well underway
04:28and approaching completion.
04:31Donors have now contributed nearly £800 million towards this effort.
04:36It's been a colossal undertaking.
04:43The team has had to remove toxic lead dust,
04:47the remains of the old lead roof left over from the fire,
04:51then clean and restore the fragile stained glass windows.
04:55They must reconstruct the roof identically
04:58and fill the three gaping holes in the stone vaulting.
05:03Rebuild the timber framework from almost a thousand oak beams,
05:08cover it with 3,000 square metres of lead sheets
05:12and raise the iconic 65 metres fire.
05:16It's the largest cathedral restoration project ever undertaken in France.
05:33Notre Dame's chief architect, Philippe Villeneuve,
05:36has led the team tasked with resurrecting the world-famous cathedral
05:40since work began.
05:46Notre Dame's chief architect, Philippe Villeneuve,
05:49has led the team tasked with resurrecting the world-famous cathedral
05:51in the past.
05:56Notre Dame's chief architect, Philippe Villeneuve,
05:58has led the team tasked with working in the past.
06:04Notre Dame has been in a state of salvage and rebuild for nearly five years.
06:25The team needs to bring together many elements from all corners of France
06:29to complete Notre Dame's restoration.
06:33Quarries and stonemasons from outside Paris need to ship 2,500 tons of stone
06:40to repair the vaults and damaged statues.
06:442,400 oak trees felled all over France are being shipped to carpentry workshops
06:49to fabricate the beams for the roof and spire.
07:08They want to reopen the cathedral to visitors later this year.
07:15Last time I was here, that felt almost ridiculously ambitious.
07:20So I'm keen to get inside and find out how things are looking.
07:26Oh, wow.
07:29It's so different from when I was last here.
07:33That was dark, it was intense, it was noisy, it was full of scaffolding,
07:37it was basically like hell.
07:39But now, it's beginning to look like a church again.
07:44It's still pretty noisy, but there's sort of serenity underneath.
07:51And there was that great big hole in the roof and it's gone.
07:55Things have really come on.
07:59Restoring Notre Dame to its former glory is a massive undertaking,
08:04demanding the unique skills and dedication of thousands of workers.
08:08The French National Heritage and Architecture Commission
08:11has ruled that Notre Dame be rebuilt exactly as it was before the fire.
08:17This means that the reconstruction must stay true to the techniques of the past,
08:23modern hands building to historic plans.
08:27This is just the fantastic thing about being able to watch
08:31such an extraordinary group of people at work,
08:34watching their curiosity
08:36and being able to follow that detective process.
08:40Since 2019, the team has successfully shored up this stone edifice
08:46and decontaminated the site.
09:01One of the team's challenges at Notre Dame was to fill the three holes in the stone vaults.
09:10First, they had to build a 33-metre-high network of scaffolding
09:16and erect temporary timber supports to prop up the remaining vaults,
09:20which were extremely fragile.
09:24Only with these in place could the team of highly specialized stone cutters
09:28then start to rebuild the collapsed limestone masonry.
09:48Notre Dame was originally built from 30 different types of limestone.
09:54Limestone is a strong and versatile material.
09:59The stone that makes up the cathedral's lower layers is heavy and tough,
10:05ideal for Notre Dame's monumental walls and pillars
10:08because it doesn't crush under its own weight.
10:13The softer and less dense stone from the upper layers
10:18is perfect for building massive-spanned ceiling vaults
10:21held aloft by limestone that's both light and strong.
10:30The teams had to repair, or completely replace,
10:34around a thousand cubic metres of stonework.
10:38Sourcing this much new stone to match the old is no simple task.
10:46When you look at Notre Dame, you can see that there are a lot of zones with small holes.
10:52These stones are marked by the presence of fossils.
10:56There are a series of holes in it.
10:57These stones are small holes in evolution.
11:03And in fact, after these holes, sometimes they part and they are empty.
11:06And it gives a particular texture to the cathedral.
11:13The limestone to rebuild Notre Dame comes from nine quarries across France.
11:19Benoit Orcholle runs one of these quarries.
11:22It produces a unique limestone that cannot be sourced from anywhere else in the country.
11:31Notre carrière soit quasiment la seule à pouvoir fournir cette qualité de pierre
11:36et surtout dans ces dimensions-là .
11:40Benoit's team must quarry and ship 670 cubic metres of stone for Notre Dame.
11:47It's the largest order his family-run business has ever received.
11:58This team has a huge job.
12:01They need to cut around 550 blocks in a very limited period of time.
12:14Cutting a block of stone calls for an expert eye and experience.
12:19They guide a 32-foot-long saw by remote control to precisely slice the stone.
12:51Once the block has been cut on both sides, Benoit uses a large,
12:56steel, steel, talon to lever it out of the bedrock.
13:00It takes skill to free the limestone and find the highest quality segments.
13:10They tie the blocks to the back of a truck and transport them to a workshop where workers give them
13:16a special wash.
13:22This sauce slices off the edge of the block to reveal the true quality of the stone inside.
13:28It's what will allow us to see the effects of the pierre, because it remains a natural material.
13:35So there are always little defects that can appear.
13:38So we can select the most beautiful blocks and have the lowest pertes possible.
13:47We choose blocks that will finally fit into the history and will not be eternally, but for us it will
13:54be eternally.
14:06Another daunting challenge that the team here face is to rebuild the roof's iconic 19th century spire.
14:13The cathedral's original spire rose 96 metres from the ground.
14:19It was clad in lead over a skeleton of oak beams.
14:23It was the most intricate element of the roof.
14:35Rebuilding this engineering masterpiece is no simple task.
14:42Workers must anchor the base of the spire on top of four stone pillars built around the ceiling vaults.
14:50From this rock solid base, they must assemble a wooden skeleton that weighs almost 500 tonnes, more than 65 metres
15:00above the ground.
15:02They must carefully wrap this in lead to protect it from the elements.
15:08And reinstall 16 decorative copper statues that are being restored, to complete Notre Dame's famous spire.
15:21The team plans to rebuild the new spire so that it's identical to the original 19th century design.
15:37The spire is octagonal in shape. Its skeleton is clad with many decorative frames that a team of specialist carpenters
15:47must carve by hand.
15:52Floral motifs decorate each of the eight faces of the spire.
15:56They're known as trefoils and quattrofoils.
16:00They're inspired by a medieval aesthetic and they're being recreated by these 21st century artisans.
16:11Carpenters need to cut 1,000 timber sections and create 2,000 joints to form the skeleton of the spire.
16:22The base alone is made up of 110 separate pieces of timber that must interlock perfectly to give the structure
16:30strength.
16:36The spire will be assembled in four separate layers.
16:42To ensure each layer fits together, carpenters and engineers first assemble all the components off-site.
16:49It takes the team four weeks to complete the first layer, which will form the base of the spire.
16:59The test assembly at this workshop is a success. All these pieces fit together just as they should.
17:07Now workers dismantle and ship the pieces to Notre Dame.
17:12On site, workers reassemble the sections on the ground so that cranes can lift them into position.
17:19With the base of the spire complete, now the team can integrate the timbers around it that make up Notre
17:26Dame's roof, known as the forest.
17:38The fire devastated the wooden structure of the cathedral.
17:42The rebuild of the roof is the most crucial element to the success of the restoration.
17:52I really hate heights.
17:58I don't like this at all.
18:00Oh, look down there.
18:02But I think this will be worth it for what's at the top.
18:05In 2019, the fire started above the roof and this huge timber structure, known as the forest because of all
18:15the wood, got completely destroyed.
18:18But now I think the forest has sprung back to life.
18:34Teams of carpenters are working flat out to install the timber trusses that make up the roof across the length
18:40of the nave.
18:43They begin from the base of the spire and move outwards in all four directions.
18:49Each bay has two principal trusses and four secondaries, which are a bit smaller in section.
18:55In the coming weeks, you have pieces that will actually insert into the stone gable between the two towers at
19:00the western end of the building.
19:02Interestingly, in the Middle Ages, they actually started the carpentry there.
19:06We're working in reverse just because of the way the site is organized.
19:10There are five or six hundred people here every day, exchanging with the other craftspeople, the other carpenters, seeing every
19:17step of the cathedral.
19:18It's fascinating every day.
19:20It's just a huge adventure.
19:25Gosh, here's the forest, and it has its own smell. Smells like fresh-cut oak.
19:33And you can see that this hasn't been done by machines. That's been done by the human hand.
19:44I think that makes it all the more lovely.
19:52They use 1,200 oak trees, mostly felled in state-owned forests across France, to reproduce the Gothic roof trusses.
20:03On site, the roof trusses arrive thick and fast.
20:07There's no assembly manual for this process.
20:09The carpenters here share a secret coded language that's hidden beneath the interwoven structure.
20:17Look at this.
20:18They've even taken the trouble to reproduce the original numbering system that was used by the medieval craftsmen.
20:27This means that this was timber number four on the south side.
20:30Nothing has been overlooked to make it just like it was.
20:38They use Roman numerals and other traditional symbols to identify the positions of the beams and where they interlock.
20:46This is a really, really old technique, old marking technique, that is understood by carpenters all around France.
20:55Thanks to this mark, we know exactly where this piece goes.
20:59This can go nowhere else.
21:03This technique was also used by the medieval carpenters who built Notre Dame's original roof.
21:09These charred roof timbers recovered from the fire depicts the same special code.
21:16Here, you have a mark of carpenters.
21:19So they are sure that this piece with this piece are together.
21:26Some of these marks hold special messages. Today, just as they did centuries ago.
21:33This mark is a bit specific. It's almost on every piece of wood in the carpentry.
21:39If I use a little there, the bubble should be centered. Yeah, I'm fine with it.
21:48The coded messages are steeped in history and so are the techniques.
21:54Hank, can you tell me how these pieces of timber have been cut?
21:57The medieval carpentry specifically, we used green wood, which means it's unseasoned, fresh off the stump.
22:05Every other beam that you see here was hand-hewn, so with an axe.
22:11So that's the telltale surface that you see.
22:13The sort of rippling, undulating signature of the axe.
22:17They're not at all cured or dried or seasoned in any way.
22:20And that's the way this carpentry was done initially.
22:27Medieval carpenters had access to vast areas of forest to select the best trees to build Notre Dame's roof.
22:35Back then, timbers were used unseasoned, shortly after felling.
22:40This green oak was soft and easier to work with than seasoned timber that had been dried.
22:47Today, the team follows the same process.
22:53Using green timber creates unique challenges.
23:00Moisture in the timber means that as it dries, its shape can slowly change over time.
23:07The market town of Chesterfield in the United Kingdom bears witness to the perils of building with green timber.
23:15It's false that the 660-year-old crooked spire at the parish church could be due to beams that have
23:23warped as they've dried.
23:25For Notre Dame's roof and spire, this precarious twisting must be avoided at all costs.
23:33The main advantage is that the wood will exert a decrease.
23:36These dimensions in these sections will be reduced, both in length and in large sections.
23:42So, the experts don't agree on that.
23:45The problem with Notre Dame is the monumentality of the structure.
23:50We are on a length of 1 mm per mètre, about on the wood.
23:55When we are on a mètre, 1 mm per mètre is not very serious,
23:59but when we are on a 10 mètre, a powder makes 10 mètres,
24:03that makes us a length of 1 cm.
24:04And then, we can see pathologies that are prejudicial to the structure.
24:12To investigate the risks of any potential warping,
24:16Emmanuel is conducting a unique experiment in the heart of rural France.
24:22Three years ago, he joined forces with timber scientists and college students
24:27to build this huge replica section of Notre Dame's roof.
24:31These green oak beams are bristling with hundreds of sensors and surveying targets.
24:39Data from the sensors so far reveals that the quality of the joints and the assembly itself,
24:45rather than the amount of moisture in the timber,
24:47is key to creating a robust structure that won't warp.
24:52Further data should allow restorers to anticipate problems
24:55and intervene long before twisting or splintering occurs.
25:02As the roof has started to settle down, has it done anything that surprised you?
25:06Yeah, invariably, as the green wood dries, it will check and twist and shrink,
25:12and that's just the way, I mean, that's life, that's the way it is.
25:15But green wood, if you're working specifically, as we were, with hand tools,
25:19green wood is much easier to work with hand tools.
25:22It's a bit like cutting a ripe fruit. As the wood dries, it becomes brittle and less amenable to hand
25:28tool work.
25:29So the wood is easier to work, but then you have to predict how it's going to behave once you've
25:34put the roof up.
25:35There are certain tensions in the wood that we've noticed that we've had to adapt to during the raising of
25:40the frame here.
25:41We've had to pull things in and hold them tight as we set them in place, because there are certain
25:47pieces that have a tendency to spring out.
25:49And so, yes, we have had to adjust a little bit as the wood is dried.
26:00As the timber roof takes shape, the team must also take precautions to protect it.
26:06It's a great work that we have to finish.
26:08We have to finish a completely rebuilt fire protection.
26:13It's thought that the 2019 fire began inside the roof.
26:17So today, they're installing a state-of-the-art fire detection and suppression system to guard against future fires.
26:25There's a whole panoply of new means, such as fires in the flames, such as a fire security security system
26:33with alarm bells, such as we've improved the water consumption of the cathedral.
26:43Workers are engineering a pioneering safety system into the rebuilt cathedral.
26:49They're erecting special fire-resistant compartments. These prevent fires from spreading quickly.
26:57They're installing heat-sensing cameras to spot fires the second they break out.
27:04And automated fire extinguishers will use a fine, high-pressure water mist to douse flames, creating next to no water
27:13damage.
27:18We realized that in a case of an incendie, like that of the 15th of April,
27:21with a fire extremely developed on the whole heart,
27:23we created a tampon, and so we avoid this effect of inflammation of the gas, just by rayonnement.
27:28We proposed to build what we call a travée coupe-feu.
27:31In fact, it's two grand murs coupe-feu at each time.
27:34So here, you have two grand murs coupe-feu, which are reliés between them and which are auto-stables.
27:49A network of sensors in the roof detect heat as well as smoke.
27:54If they detect a fire, the new system should be able to extinguish it before it spreads.
28:20The innovative system should protect Notre Dame's great forest from future threats of fire.
28:3550 metres below the carpenters constructing Notre Dame's new roof,
28:39another team of experts is unearthing the cathedral's ancient past.
28:45Every week we discover a new hidden corner of the building,
28:48where we go into a place that we haven't seen before.
28:51We see what the archaeologists have uncovered, skeletons everywhere.
28:54The work to restore the structure's historic footings offers an unprecedented portal into the past.
29:04Archaeologists have uncovered a treasure trove of findings hidden beneath the cathedral floor.
29:20They include 400 burials, dating back nearly 800 years, and at least 10 preserved sarcophagi, including a 14th century clergyman.
29:36Their work is also revealing ancient engineering secrets.
29:51The
29:52engineers are now using the historic heating ducts to house modern electrical cables.
30:09The building of the modern cathedral requires an enormous amount of supplies.
30:13The building of the modern cathedral requires an enormous amount of supplies.
30:29Delivering materials to the centre of Paris is one of the team's most complex logistical challenges.
30:43To avoid creating gridlock in the city, they make use of the waterway that surrounds Notre Dame, the river Seine,
30:51and deliver the stone by barge.
31:03Notre Dame sits on an island in the river.
31:17Notre Dame sits on an island in the river.
31:29The
31:45Docking the barge safely at the congested delivery point requires a steady hand.
31:50We are here. Notre Dame is here.
31:54Skills like this have guided materials to Notre Dame
31:57for hundreds of years.
32:00When Notre Dame has been built,
32:04it was a ship ship.
32:06And we reproduced exactly what the old ones did,
32:10but with more modern materials.
32:13Yes, I'm going to slow down.
32:18Eric can dock his barge right next to the work site,
32:23where Notre Dame's cranes can unload the stones.
32:39The four of us are under the sea.
32:39The barges like Eric's are delivering more than 55 tonnes of stone,
32:43alongside shipments of lead,
32:45to complete this historic rebuild.
32:48The B4. Thank you.
32:50And then the B4 is on the road.
32:52The B4 is on the road.
32:52It's good to work on a boat.
32:55Well, it's good to work on a ship.
32:56You can't see it, it's good to work on a ship.
32:58We can see it.
33:08Eric will make dozens of journeys like this over the next eight months.
33:13It's a symbol for France.
33:21It's a strong state. There's a fierté, enthusiasm, a unity, a union of all.
33:27We're all united to the goal of giving the cathedral to all those who love it.
33:33We're proud of the history of Notre Dame.
33:47Back up on the roof, the team is gearing up for the next critical stage of construction.
33:53They must cover the roof and spire with protective sheets of lead.
34:00Plomb is a mode of coverage that is frequent in the great historical monuments.
34:06It's important for authenticity reasons.
34:09It's a metal of great quality because it's very durable and because it's durable.
34:17To acquire the quantities of lead they needed, the team had to look outside France,
34:24across the English Channel, to this factory in Leicester.
34:30Workers here produce special sheets of lead cast on a flatbed of sand.
34:36It's a technique that's been used for centuries.
34:39Sand's been used from the Roman times to produce lead sheets
34:42and there's only a small number of manufacturers in the world that manufacture sandcastle lead.
34:49The process today is pretty much as it was originally.
34:54This method of casting lead on sand was developed by medieval engineers
34:59but has almost died out across Europe today.
35:02It requires expert skills.
35:10All the skill and knowledge is within the person manufacturing the lead.
35:14The first step is to lay down a bed of fine moulding sand on top of the casting table.
35:24Down to the bottom there, it's only a timber board and that's got holes in to allow the steam to
35:29come through.
35:30When the molten lead goes on top, the steam needs to escape
35:34because otherwise if the steam comes up and we've only got a small layer of molten lead on top,
35:38it will force the steam out of the lead and causes splits in the lead.
35:41So it's quite important to get everything perfectly done.
35:47The team packs down the sand to even out the surface so the molten lead sets smoothly on top.
35:56The guys have pressed it down so it's a nice consistency all the way along.
36:01Copper flame is used just to give that perfect finish on top without any blemishes or marks.
36:07The sand, if it's left not quite perfect, it could pick up a small bit of sand
36:12which might leave a small pinhole or impurity in the lead.
36:15So making sure this bit's perfectly smooth and that we've got a consistency of the lead sheet all the way
36:20through.
36:24Next step is to load the furnace with lead ingots.
36:28These are made from lead recycled from scrap yards and discarded batteries.
36:32The ingots are refined to 99% pure lead.
36:37The furnace is tapped to allow the lead to pour into the head pan.
36:42The temperature of the lead now will be around about 360-370 degrees.
36:48And that allows it to cool down. We're looking to get to about 327 degrees.
36:54You can see it's slightly setting as they actually move the lead.
36:57That literally is because we are just above the melting point.
37:00Once that's all clear, we're ready to pour.
37:03This head pan is controlled by a hydraulic ram.
37:06The hydraulic ram has a speed sensor on it so it can actually speed up the way the lead tips
37:11or slow it down.
37:12Which also helps with achieving better thicknesses and a more even consistency of the sheet on the table.
37:23The lead is actually poured down the sand at about 327 degrees.
37:27As it hits the sand, it instantly sets.
37:37As you watch the strickle run forward through the molten lead,
37:40it's physically set in behind creating a brand new lead sheet.
37:57Every throw is different. It's a handmade product.
38:00What we're looking for on a lead sheet is small pinholes.
38:05Looking for potential cracks, small things you wouldn't notice with the untrained eye.
38:14You can see the guys are now rolling the finished sheets, still be warm.
38:17They roll pretty easy whilst they're nice and warm.
38:20And the craftsmanship and skill of the guys making the lead is really important.
38:24They've been doing it for many years now, the skill they've got in manufacturing the lead.
38:28You can't actually physically teach it, you can't give anybody a manual and say this is how you do it.
38:32It's a case of getting involved and basically having the skills just to do the process over and over again.
38:37The team here has six months to make more than 280 tons of lead for Notre Dame.
38:44Workers can now cut, bend and mould these sheets over the timber framework to make the cathedral's roof and spire
38:52watertight.
38:57There's now just 11 months to go until Notre Dame's doors are due to open to the public.
39:05Teams are working around the clock to assemble the timber work and lead for the roof and spire.
39:11Cut and install the limestone for the vaults.
39:14And clean and restore the cathedral's ornate windows.
39:20It's a unique and complex tapestry.
39:26The architecture, the engineering, the art, the stained glass, those amazing gargoyles just come together collectively to make that miraculous
39:36building.
39:42One of the most intricate tasks for the team of stonemasons here is to repair and restore the statues and
39:49friezes high up on Notre Dame's roof and walls.
39:53These gargoyles and chimeras have overlooked the city and protected the cathedral for hundreds of years.
40:03Medieval architects designed the gargoyles to help channel rainwater away from the building's walls and prevent the stone from eroding.
40:16The chimeras are purely decorative features.
40:20They're shaped in the form of mythical beasts created to evoke a sense of mystery and ward off evil forces.
40:30Many of these sculptures were designed and installed by master architect Urgen Viollet-le-Duc who oversaw a major restoration
40:38of Notre Dame in the 19th century.
40:50Many of the detailed features on these iconic sculptures have been eroded away by the elements over time.
40:57Today, as part of Notre Dame's grand 21st century restoration, teams are removing all of the sculptures.
41:10They're taking them to this special 200 square meter workshop at the foot of the cathedral.
41:25Oh, my goodness.
41:29This place is a treasure trove.
41:32It's absolutely stuck with sculptures.
41:39The restored statues are being used as a template to carve a brand new family of limestone sculptures.
41:54The new sculptures must be identical in size and shape to the original for installation in the cathedral.
42:11They must adopt different techniques to restore and re-sculpt depending on how damaged the stonework is.
42:19We discovered that it was a thousand pieces.
42:23We had, naturally, images.
42:26We did a little study to see what we had.
42:31We did a whole work of research.
42:37We tried like a puzzle.
42:39We tried the small pieces.
42:42It went there, it went there, it went there, and it went there.
42:44It was a pretty fun work.
42:47I'm going to preserve and restore what was existing.
42:53So I'm going to look for the best way to restore the sculptures.
43:00Viollet-le-Duc's original 19th-century statues will be treasured for future display.
43:11Some sculptures, like this gargoyle, have missing features.
43:16Restoring the lost details to help them make identical modern replicas requires detective work.
43:38They need to repair the old damaged sculpture before they can create its replica.
43:45The first step is to apply layers of special stone mortar.
43:49So this is a statue to apply the mortar.
43:52And this is a stonework to apply the mortar.
43:59To recreate the most fragile and shattered stone sculptures, engineers have developed pioneering techniques.
44:08The team scans the damaged sculpture and creates a three-dimensional computer model.
44:17They then 3D print this model, life-size, in a soft foam.
44:23They then use plaster of Paris to precisely reconstruct features that have eroded or been destroyed.
44:31Only then can the sculptors get to work.
44:34To carve out the brand-new replica statue from hard limestone.
44:50The new sculptures must be carved from the hardest variety of limestone, to make sure they're strong enough to hang
44:57unsupported and to withstand the elements outdoors.
45:01With their craft and ingenuity, these talented sculptors are carving hundreds of different decorative elements, which will permanently adorn the
45:12restored cathedral.
45:14When the project is finished, will you feel sad?
45:17Sad? No.
45:18Sad? No.
45:22Sad? No.
45:24Sad? No.
45:25Sad? No.
45:26Sad? No.
45:26Sad? No.
45:26Sad? No.
45:28Sad? No.
45:31Sad? No.
45:32Sad? No.
45:33Sad? No.
45:35Sad? No.
45:35Sad? No.
45:36Sad? No.
45:36Sad? No.
45:36Sad? No.
45:38Sad? No.
45:39Sad? No.
45:39Sad? No.
45:40Sad? No.
45:40Sad? No.
45:40Sad? No.
45:40Sad? No.
45:41Sad? No.
45:42Sad? No.
45:42Sad? No.
45:43Sad? No.
45:44Sad? No.
45:48what they've done they've really matched in the new stone to the old and given
45:54the old a magnificent queen too they were aiming for you to get the idea that
46:00the cathedral was just finished yesterday a full-on restoration and they
46:04have achieved that it's remarkable the care that's been taken
46:13it's taken the dedication of nearly 1 000 workers to restore notre dame
46:18on a sur ce chantier des entreprises d'une d'une compétence et d'une qualité incroyable
46:26tant technique d'ailleurs que humaine on est tous tendu pour la réussite de cette catenale qu'on
46:31aime tous je viens sur ce chantier travailler sur une magistrale merveille que j'aime tant
46:36avec des gens que j'adore et ça c'est formidable
46:50at the timber workshop in western france the carpenters have cut hundreds of beams over six
46:57months now they're facing a challenging task they must create the framework for the most complex
47:04section of the roof the curved apps that crowns the rear of the cathedral
47:15the first step is to draw a precise outline of each truss on the ground this allows the team to
47:26assemble
47:26the whole frame inside the factory to ensure that all the timbers and joints precisely interlock
47:49it takes two months to erect the apps in the workshop
48:05once dismantled trucks can ship it to notre dame where it will be reassembled on a souvenir d'atelier
48:31on site it's taken carpenters four months to install nearly a hundred trusses across the
48:43whole roof the whole roof the trusses cover almost all of the transept as notre dame's iconic forest bursts
48:53back to life valentin and his team need a head for heights working 60 meters above the ground to make
49:05their task even tougher they're now installing the most complex part of the roof the curved apps that crowns
49:12the rear of the cathedral
49:20the biggest challenge on the apps which is just behind me because this is a part where a lot of
49:27wood
49:27pieces are coming together and the joints are particularly complicated to do we can see some
49:33that are not typical so that's what is most complicated for me to complete the curved roof
49:42framework over the apps valentin's team must assemble two tiers of wooden beams that radiate out like the
49:50spokes of a huge umbrella then they must install a frame with a spike on top that'll hold up the
49:59cross
50:00over the apps finally they must attach the 20 rafters which taper precisely at the top and fit together
50:13tightly to form a perfectly curved half cone at the rear of the roof this is a big test the
50:27timber work for
50:28the apps fitted together in the workshop but will it work up here
50:38it takes valentin and his team seven days to fit this giant jigsaw together
50:51today they reach a milestone the final laughter needs slotting into place
51:00the detailed planning and hard work of the carpenters has paid off
51:09Notre Dame has a roof once more
51:13it's a unique project we know that we won't see this view ever again we are really proud of what
51:19we produce
51:29over on the central section of the roof inside this tower of scaffolding workers are now gearing up
51:36to install the uppermost sections of the spire the decorative frames that make up the octagonal spire slot
51:45into place in december 2023 the reconstruction reaches its peak the team gathers to install the top of the spire
51:57to crown this monumental achievement
52:01the metal cross lands on top and the skyline of paris welcomes the new Notre Dame
52:16with the timber spire and roof frames in place the team must now prepare the lead covering for installation
52:26they mold the rolls into individual sheets that will cover the roof and spire
52:33they trim them into angular pieces that will protect the body of the spire
52:39some of the more complex shapes such as the gargoyles and delicate ornamentation must be cast from molten lead
52:49altogether they must tailor make over 3 000 lead pieces a real feat of heavy metal haute couture
53:11julienne must fit 120 tons of 3.5 millimeter thick lead sheets to cover the entire surface of the spire
53:20the sheets should fit over the spire like a jigsaw
53:42the malleable quality of the lead allows the team to bend and shape the material to cover the intricate angles
53:49and corners
53:53I want to mark the angle at the interior and the first time with a bat.
54:03I have a second bat, which we call a bourseau. It's a bat that forms an angle a bit more
54:08vif and it comes with the finishing. It's the cover that we know from the
54:13modern age. It's about the same technique. It's just that after that it evolved,
54:16we didn't have any caoutchouc. We didn't have any resin in the middle. It was a baton wood.
54:22The lead sheets must fit tight to the timber work to create a watertight protective cladding.
54:28This is really the last pass.
54:34Once the cladding is fitted, they can install the spire's decorative features.
54:40It takes Julien and the team two months to cover the top half of the 96-metre spire.
54:46with the lead that will protect it for centuries to come.
54:50It's something that's not a tradition. It's the main piece of the cathedral.
54:56There's a certain certainty to say, when it's finished, we've been there and we've done it.
55:11With the main construction works reaching completion, teams prepared the final elements to restore Notre Dame's legendary beauty.
55:20It's true that every time I come here, it's extraordinary.
55:24These 16 copper statues from the spire were miraculously spared from the fire, having been removed for restoration only days
55:32before the inferno broke out.
55:34We were going to dismantle these statues on November 11th of 2019.
55:39And unfortunately, four days later, there was an explosion.
55:42We had the chance.
55:45Coppersmiths have painstakingly restored the statues, which are now ready to regain their rightful place on Notre Dame's spire.
55:55And to say that there are millions of tourists who will pass in front, wow.
56:02Inside the cathedral, the final touches are taking place.
56:06The decorative plaster walls, vaults, and shrines are painted by hand to a luster that hasn't been seen in generations.
56:15To match expectations, every detail must be perfect.
56:20Our family of Paris is a monument classed, a world heritage of humanity.
56:28For the whole team here, rebuilding Notre Dame has been the challenge of a lifetime.
56:36It's an immense element of particularly savant and extraordinary, of wood, of steel, of metal, of glass.
56:43There is an alchemy that is created, and that's why I work.
56:47Over the course of the rebuild, teams have cut and carved more than 2,500 tons of stone, shaped and
56:55interlocked more than 2,000 pieces of timber.
56:58To say it's the chance of a lifetime is a huge understatement.
57:02Just to be here on site every day, it doesn't get old for me.
57:07Cleaned and reassembled 3,000 square meters of stained glass.
57:11It's magnificent, the beauty of this beautiful, look at it, it's incredible, for me it's incredible.
57:20And rebuilt more than 50 statues.
57:25It's been such a privilege to spend time in the cathedral, and what dedication from the architects, the restorers, the
57:33carpenters, all the craftspeople who've worked so hard to put it all together.
57:38And on such a tight deadline too.
57:41But it does seem like their dream of reopening in 2024 will be a reality.
57:49I think it's a stunning success.
57:51This project will have its critics, but nobody can deny the determination, the skill, the will that's gone into bringing
58:01the cathedral back from the ashes.
58:08I think Notre Dame is part of their humanity, their history, their memory and their memories.
58:18It's like the tower Eiffel, it's like the statue of freedom, it's like the Taj Mahal.
58:23Notre Dame is part of us.
58:25We all...
58:26It's like a nightmare, everyone.
58:39Remote tribes facing extreme challenges.
58:42Bruce Parry immerses himself.
58:44Press red to watch now on BBC iPlayer.
58:47And what happens when you find a Banksy on your wall one morning?
58:50The Banksy story, when Banksy comes to town.
58:53On the new podcast, on Sounds.
58:55.
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