Notre Dame was classified as a World Heritage Site by UNESCO in 1991. The cathedral is laden with national, religious and cultural symbolism, and is a landmark for Parisians and the millions of people who visit the city annually. Consequently, the fire aroused enormous upheaval in large parts of the world, and led to a feverish reconstruction zeal that engaged all of France. The pattern is familiar from history. Even during the Middle Ages, cathedrals burned, and when new money was injected into half-dormant building projects, new construction techniques and stylistic elements could often emerge. The new was to be higher, bigger and more magnificent than what the flames had taken.
After the fire
Immediately after the fire it was made clear that Notre Dame would be rebuilt. But an intense debate arose about how and to what. There was discussion about whether to reconstruct the medieval roof and the 19th-century neo-Gothic spire with modern materials and a contemporary expression, or to recreate them exactly as they were before the fire. In one camp were those who argued that if nothing new was added, one would not be looking forward and then the church would lose some of its meaning. Others argued that Notre Dame, after the architect Eugène Viollet-le-Duc's renovation in the 19th century, had become a memorial to history and a central monument to France's cultural heritage, and that if anything were removed or changed, the building would lose its identity and significance.
In the end it was decided that everything with a few exceptions would be recreated as it looked before the fire. The faithful reconstruction of Viollet-le-Duc's spire and the medieval roof structure, known as la forêt (the forest), would furthermore be done with original materials and in some cases old construction techniques, but using contemporary measuring and calculation techniques. These provide a precision far beyond what previous generations had the possibility to achieve, and a much faster and more controlled construction process than would otherwise have been possible.
The first two years were devoted to stabilising the building and clearing after the fire. The restoration began in 2021 and the cathedral was reconsecrated on 7 December 2024. However, the restoration is not expected to be completely finished until the end of 2026.
The work was led by Philippe Villeneuve, assisted by Rémi Fromont and Pascal Prunet, all titled chief architects for historical monuments by France's Ministry of Culture. The project involved approximately 2,000 craftspeople and over 250 companies. Initially it was estimated that the reconstruction of Notre Dame would take 10–15 years. But fortunate circumstances meant that the entire gigantic and complex reconstruction work took only five years.
In 2010, detailed laser scans were made of the entire cathedral. After the fire, similar scans could quickly be made and the three-dimensional models thus obtained compared with the model of how the cathedral looked before the catastrophe.
This meant that detailed drawings and specifications could be produced in a short time that could be used in the reconstruction work. Crucial for recreating the construction of the famous timber roof, La forêt, were the exact measurements and drawings made as recently as 2014 by Rémi Fromont and Cédric Trentesaux (chief architect at L'École de Chaillot). They discovered that no drawing of the 800-year-old roof structure had actually ever been made. In 2014, Rémi Fromont was a student at L'École de Chaillot, a school that amongst other things specialises in training architects in the preservation of France's architectural cultural heritage. Now he is chief architect for historical monuments and one of those responsible for saving the cathedral.
Recreating the roof structure
The Gothic timber section in la forêt was exceptionally large for its time and extraordinarily well made. The nave's roof structure, above the stone vaults, was 75 metres long, and that above the choir 32 metres. The width was at most 14 metres and the height 10 metres. The construction consisted of hand-hewn slightly conical beams, which were somewhat thicker where they were joined together, which provided increased strength in the joints. Such beams are much harder or impossible to create with modern saws, says Fromont in an interview in the newspaper Les Echos. Hand-hewn beams are also mechanically stronger than sawn ones, because they follow the wood's fibres.
Thanks to the meticulous measurement and drawing, it proved possible to recreate an exact replica of the roof structure. First a model at 1:20 of the entire construction was created. Then a roof truss was built at full scale. Then all the measurements were fed into the digital models that were used to finally confirm that the drawings could be used to recreate the cathedral's roof structure. Finally, 1,300 drawings and 500 templates at scale 1:1 were produced in a very short time. With the help of these, the size of the trees needed was determined and templates were made for each part that was to be hewn. Since they needed to work from fresh timber, the exact dimensions in which all parts should be hewn were calculated, so that after having dried and shrunk in place in the roof structure for 20–30 years, they would become identical to the original roof trusses.
The reconstruction of the roof structure was done in the same way and with similar tools as in the 12th century, with axe and chisel, hand saws, auger and wooden mallet. Each beam was shaped individually and they were joined with wooden pegs. No iron was used. The entire timber construction was recreated by hand in eight months. The ten-metre-high roof trusses were then allowed to dry outdoors for 18 months for the best possible dimensional stability, before they were lifted into place in Notre Dame in January–March 2024.
The hunt for the perfect trees
When you hew, in the same way as medieval carpenters did, the idea is to keep the log's heartwood in the middle of the beam and remove as little material as possible. To succeed with that, you must choose trees where the diameter and length correspond to the size of the finished beam. Finding the right trees proved, however, to be significantly more difficult than those involved had reckoned with. The requirements were high. The tie beams in the roof trusses were 13 metres long, and to hew out replicas of them, the principal and diagonal struts and the hammer beams required tall, straight, slender completely flawless trees, without knots, twists or the slightest blemish on the bark. Such trees were what the medieval builders had used.
Those responsible for procurement searched a total of 600 hectares of oak forests throughout France. Each tree was selected according to its diameter, its straightness and its length, and it turned out that only one to two trees per hectare were suitable. There are plenty of oak forests in France, where the trees grow significantly faster than at our latitudes. Annually, 2 million cubic metres of oak are felled there. Despite this, debate also arose about whether it was reasonable from an ecological point of view to cut down oaks to rebuild Notre Dame. In total it was about 1,200 oaks that needed to be felled. That corresponds to less than 5 per cent of the oaks that are annually felled in French state forests.
Notre Dame's roof trusses
We often think of the Gothic cathedrals as primarily stone buildings, but timber construction technology also took significant strides during the 13th century, which the roof trusses in Notre Dame bear witness to. The earliest roof trusses were assembled from many short pieces of timber, which were easy to handle and find timber for, but complicated to assemble. The result was a somewhat too flexible construction. For the subsequent roof trusses, from the beginning of the 13th century, a combination of very long and shorter beams was used, which gave a much more solid construction. But it must also have been substantially more difficult to obtain and transport the timber, and to hoist up and assemble the roof truss parts. The longest beams were 14 metres long.
The measurements from 2014 showed, however, that the construction was not completely optimal. Even though the construction was similar, the roof trusses over the choir would have fitted better over the nave and vice versa, something that was not corrected in connection with the renovation. The new ''Forest'' (la forêt) is thus a historically correct replica that will be able to last for many hundreds of years – especially as it is now equipped with fire protection.
The spire
Notre Dame's original spire was constructed during the 13th century and functioned as a bell tower. The tower was taken down during the French Revolution for safety reasons. The spire that was destroyed in the 2019 fire looked completely different from the original and was Viollet-le Duc's neo-Gothic creation from 1859-1860. The 96-metre-high construction was ingeniously designed from 500 tonnes of oak timber, covered with 250 tonnes of lead sheets. Everything rested on an octagonal base that was carried by the transept's four pillars. The drawings still existed, but it was still a considerable challenge to find oaks of the right quality and size, manufacture, transport and lift the spire's parts into place. Just as for the roof structure, traditional hand tools were used together with modern measuring methods for optimal precision.
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Photo:
Jean-Francois Monier/ TT
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Photo:
Alain Jocard/TT
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Photo:
Sameer Al-Doumy
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Photo:
David Bordes © Rebâtir Notre-Dame de Paris
Text: Carl Johan Liljegren Photo: TT, Art Graphique & Patrimoine, Rebâtir Notre-Dame de Paris
