FIRE REVEALS ARCHITECTURAL FIRST

The massive re that engulfed Notre Dame Cathedral in Paris four years ago has revealed a previously unknown aspect of the iconic building. Following the blaze and neartotal destruction of the famous landmark in April 2019, when much of the structure collapsed or was laid bare, a

Secrets of Notre Dame Construction Uncovered

huge restoration project was begun to restore it to its original glory. In the process, archaeologists have discovered that it was the rst Gothic cathedral in which iron staples were used extensively throughout construction to provide structural reinforcement.

e construction of the cathedral in the heart of the French capital began in e blaze in 2019 exposed iron staples used to hold the cathedral’s stone blocks together, with some revealed in the frame of the building, while others fell smouldering to the ground in the heat of the re.

1160, and was not completed until almost a century later, and as the tallest building of its time with vaults reaching up to 105 foot high, modern-day architects have until now struggled to explain how its relatively thin walls could stand so tall while retaining structural integrity.

“Notre-Dame is now unquestionably the rst known Gothic cathedral where iron was massively used to bind stones as a proper construction material,” a study published in the journal PLOS ONE concludes.

Study

Maxime L’Heritier, an archaeologist at the University Paris and the study’s lead author, said some elements of the building’s construction remained unknown, even a er all these centuries.

It was not clear how the builders “dared — and succeeded — in putting up such thin walls to such a height,” he said. Lacking much documentation from more than 900 years ago, “only the monument can speak” about its construction, he added.

L’Heritier’s study highlights the various architectural features that contributed to the construction of such a tall structure, saying: “All these architectural feats were indeed crucial for the construction of Notre-Dame to succeed. But were they su cient?”

He explains the lack of understanding to date behind Notre Dame’s previously undiscovered iron reinforcements: “ e contribution of the types of materials was never really addressed among the construction techniques. ey are recorded merely as lists in the remaining folios of the archival record books, even if sometimes the reason for the choice made is succinctly described, most of time about the stones (proximity of the quarry, colour and workability).

“Nevertheless, the material properties clearly determine the structure’s stability. e implementation of iron and its functions in the initial design of several 13th century cathedrals is now well known, but has never been explored this far in the case of Notre Dame. As in all these monuments, iron also played a major role in the cathedral’s elevation from its earliest construction campaigns.

“ e use of iron armatures was long considered as a feature of late restoration (usually 19th Century) and was therefore rarely studied in the past. Up to the 1980s, following this opinion, certain monuments bearing such iron reinforcements were mutilated, such as Beauvais cathedral where iron tierods were removed, leading to major structural issues for the monument. So far, the earliest Gothic monuments in which iron armatures have been discovered were built in the beginning of the 13th Century, or in the late 12th Century, but only small iron pins were sometimes used inside some of the columns.”

Proof

He explains that through scienti c dating of the iron used, it can be proven that they were indeed incorporated into the design and build of the structure from its earliest stages.

“ e results show that all samples are contemporaneous with the construction phases of Notre-Dame in the middle of the 12th or beginning of the 13th Century, thus indicating that they were probably produced and implemented at the beginning of the erection of the cathedral. e results also show that the samples taken are dated as not later than the 1160s, whereas the top wall samples can be possibly later than the 1200s, suggesting approximately a 50 years shi .” e cathedral could have more than a thousand iron staples, the study said, ranging from 10 to 20 inches long, and some weighing up to a few kilos. ey were found in many di erent parts of the cathedral, including in the walls of the nave, the choir tribunes and in parts of the cornice.

“ is is the rst truly massive use of iron in a Gothic cathedral, in very speci c places,” L’Heritier said.

Iron staples have been used in construction since Antiquity, including in Rome’s Colosseum and Greek temples, but in those cases they were simply used to keep large stone blocks secure on the lower oors.

Notre-Dame has a “much more dynamic conception of architecture,” L’Heritier said.

Iron would go on to be used in this way in numerous cathedrals across France.

More than 200 scientists are working on restoring Notre-Dame, whose iconic spire is expected to back in place by the end of this year.