Architects and artisans have been working tirelessly to completely rebuild the fire-ravaged roof of the iconic Notre Dame Cathedral. They also chose medieval-era techniques to restore the roof to its original form accurately. 

And working with hand axes to assemble numerous oak beams for the exact resurrection of the wooden framework has been comparatively more difficult for modern carpenters. "It’s a little mind-bending sometimes,” Peter Henrikson, one of the carpenters, told AP.

Use of medieval-era techniques

Using medieval-era skills is said to be a "deliberate choice" despite the availability of modern tech solutions. The iconic Notre Dame roof caught fire in 2019, and renovation work has been ongoing ever since.  

“The aim is to pay tribute to the astounding craftsmanship of the cathedral’s original builders and to ensure that the centuries-old art of hand-fashioning wood lives on,” AP reported. 

Carpenters and architects have been given a December 2024 deadline to restore the ravaged roof. They've also used computer models to speed up the ongoing reconstruction work. 

Computers assist carpenters in creating detailed drawing plans. This is especially useful for ensuring that the handcrafted chiselled beams fit together properly. 

They reported a major milestone in May after the perfect assemblage of timber frames, which was put together at a workshop in western France's Loire Valley. The architects also performed a dry run to test its fit, and it is now ready to be installed atop the cathedral. As many as 1,200 timber trees were chopped to create this frame.  

“The objective we had was to restore to its original condition the wooden frame structure that disappeared during the fire of April 15, 2019,” architect Remi Fromont told AP. In 2012, Fromont created detailed drawings of the landmark's original wooden framework.

He adds that the rebuilt work “is the same wooden frame structure of the 13th century. We have exactly the same material: oak. We have the same tools, with the same axes that were used exactly the same tools. We have the same know-how. And soon, it will return to its same place”.

The fire revealed hidden architecture

In April 2019, a massive fire ripped through this 12th-century cathedral for unknown reasons. This 32-metre-high cathedral was one of the tallest in the 12th century.

The fire episode allowed archaeologists to examine the landmark's hidden architectural details. 

French researchers discovered iron clamps possibly used during the building's construction. It was noticed that the iron staples still held the cathedral's stones together.

Archaeologists discovered thousands of iron staples placed throughout the cathedral, some of which date back to the early 1160s.

These findings suggested that Notre Dame is possibly the world's oldest church building to use iron reinforcements. 

Bind iron stones together 

The researchers have determined that Notre Dame is "indisputably" the earliest known cathedral of Gothic-style architecture to have been initially constructed using substantial usage of iron to bind stones together, according to the study published in PLOS ONE. 

The analysis could also deepen understanding of the iron trade, circulation, and forging in 12th and 13th century Paris. 

At a height of 32 metres when it was built in the middle of the 12th century, Notre Dame was the tallest structure ever constructed. According to earlier studies, this record may have been made feasible by integrating several architectural advances. 

However, despite the widespread usage of iron reinforcements in more recent cathedrals and efforts to restore historic structures, it remained unknown what function iron may have served in Notre Dame's construction – until now. 

Maxime L'Héritier of Université Paris 8, France, and colleagues could access previously concealed parts of Notre Dame that hold clues to the possible use of iron in its construction due to the 2019 fire and subsequent restoration. 

The researchers collected material samples from 12 iron staples used in the tribunes, nave aisles, and upper walls of the building to hold stones together. They used microscopic, chemical, and architectural investigations along with radiocarbon dating to learn more about the staples. 

The team's research indicated that during the construction of Notre Dame in the 1160s, iron staples were undoubtedly utilised throughout the building process, making it the first building of its kind to do so.

'A new form of architecture'

"Radiocarbon dating reveals that Notre-Dame de Paris is indisputably the first Gothic cathedral where iron was thought of as a real building material to create a new form of architecture," the authors said in a press release. 

"The medieval builders used several thousand iron staples throughout its construction," they added. 

The analyses also offer details that may increase understanding of the iron trade, circulation, and forging in 12th and 13th century Paris when combined with other archaeological and historical facts from that period.

For instance, the authors highlighted that several staples appear to have been created by "welding together" pieces of iron from various supply sources.

They state that additional analyses of Notre Dame materials and a thorough database of historical iron producers in the area are required to corroborate and build on these novel discoveries regarding the medieval Parisian iron market.

More than four years have passed since a fire ripped through the cathedral in Paris on April 15, 2019. The 12th-century landmark is currently undergoing reconstruction, with plans to reopen to both visitors and churchgoers in December 2024, according to French officials.