The Notre Dame has been scarred by fire. As the extent of the damage becomes clear, it is time to think about how to rebuild this sacred monument that has seen so much history. A design competition has been announced, and close to a billion euros has been donated. We propose a strategy to rebuild Notre Dame in a modern way, that maintains the soul and layered history of the building.
President Macron has pledged to restore Notre Dame fully. The idea floated by Mr. Macron seems to be to restore the church exactly like it was, and use carpenters and stoneworkers to remake to church to its exact origins. Ideally reconstruction finishes before the summer olympics of 2024, which is 5 years from now.
That’s not an easy task. There are several issues with rebuilding a cathedral that involved such skill and materials, most of which are long gone.
Jean-Claude Bellanger, secretary-general of Les Compagnons du Devoir, an organization that provides training in manual trades estimated to Associated Press that at least 400 craftsmen need to be trained. These are master stone-cutters, woodworkers, quarrymen, roofers, sculptors and other craftsmen. The specialized labour simply isn’t available in France and he estimates it would take a decade to train a crew.
Notre Dame was built out of wood and stone. The oak wood comes from old forests that were cut in the 13th century. These forests do not exist in France anymore according to Bertrand de Feydeau, vice president of preservation group Fondation du Patrimoine in his interview with France Info Radio. Oak trees of that size are long gone, and will need to be imported, if they can be found at all. Most likely craftsmen will need to resort to finding different trees or use modern techniques such as laminating.
The stone is a typical Parisian stone, a local material called Lutetian limestone, which was dug from now abandoned mines. Almost the entire city is built in this stone. It’s the material that gives the city its uniform, warm creamy grey look and contributes to its nickname the City of Light. Haussman’s grand renovation of Paris relied on this Lutetian limestone, just like the builders of the Louvre and the Place de la Concorde.
Now the main old mine is underneath the 5th, 6th, 14th and 15th arrondissement, and the smaller mines are also covered by the city’s expansion over time. Some mines are used as the ‘Ossuaire Municipal’, also commonly known as the catacombs of Paris. The mining industry has moved out of Paris since, and the quarry is deserted.
And even so, if there is access to the best craftsmen, trees are imported from New Zealand, Paris stone is mined from new quarries, then there is the philosophical question: is a reconstruction as good as the original? Isn’t a copy just a fake? Simply copying, pretending there never was a fire, would be a historical forgery.
Currently there is a big hole in the roof and the spire is gone. There is a big pile of rubble on the floor of the nave and the crossing. It consists of pieces of Paris stone, charred wood, ash and dust.
The original design of the church is saved, as now deceased American professor Andrew Tallon did a full 3D scan of the cathedral back in 2000. The video below shows the incredible detail that is visible in this 3D scans.
Why not use that?
What if we reuse what is left? What if we take the remains of the Notre Dame and use them to build her up again? What if we take the stone that has seen so much history and not simply discard it but reuse it, and with that maintain the soul of the building?
Our proposal is to combine old materials and new technologies. We propose to take the rubble and turn it into a new stone of Paris. We can collect the ash, the dust and damaged stone and turn them into a 3D printable powder. The powder will have the colour of the Parisian stone yellowish grey, mixed with the charred remains of the wood. We can then use this powder, together with the existing 3D scans, and directly 3D print the lost parts of the Notre Dame.
This is not just a dream. For the last couple years we have been creating stone 3D printing materials at our company in Rotterdam. The image below shows Le Stryge, the famous demon originally created by Viollet Le Duc in the 19th century, who watches over Paris. We reprinted Le Stryge using a 3D scan, and using a material that is a combination of lime stone and ash, the exact materials that are available on site.
We can create a modern interpretation of a traditional workshop, a modern fabrica ecclesia, on the site of the church itself. A workflow can be created where rubble is crushed and mixed, directly 3D printed and then installed by the craftsmen. It can be a living, interactive and growing space of creation, culture and religion that can be visited by people all over the world. People can contribute directly to the restoration by adopting statues and building parts, and see new parts come to life before their eyes.
We would crush and mix the stone and ash into a fine powder, that is loaded into a large inkjet 3D printer. The printer deposits thin layers of the powder and prints an ink on top of each layer, solidifying the powder to each other. Prints are then depowdered, and can immediately be put into the building.
The closeup below shows what a mixed material of ash and Paris stone could look like in more detail, based on experiments in our lab. The streaks of ash are visible in the sculpture, making the fire a physical part of the reconstruction. The 3D printed material is durable against weather and mechanically sound, and would add upon the layered history of the cathedral.
We could start reconstruction almost immediately, without need for new expensive and hard to find materials. We also don’t need to train a large crew. The Notre Dame would be able to reopen within several months, and people would be able to participate and interact with the restoration. We wouldn’t need to discard and waste the materials that have so much history embedded inside them, and can instead reuse them for the renovation.
We would like the Notre Dame to rise from its ashes like a phoenix. The fire is now part of its long history. The building should show its layered history proudly, and show the world that it has conquered it. The fire can also be the future of Notre Dame.
Eric Geboers & Matteo Baldassari
Architects & founders of CONCR3DE