Notre Dame fire revealed cathedral’s innovative use of iron

When a fire destroyed Notre Dame Cathedral’s famous spire and much of the roof in 2019, the immediate destruction and subsequent repair efforts unexpectedly revealed large steel staples holding many of the stone blocks together. of the building. Analysis has now shown that Notre Dame was the first Gothic cathedral to use such steel reinforcement throughout its structure – a fact that highlights the iconic building as a high-tech, modern marvel of its time. this.

“You realize that they were building things like the Empire State Building in 1930, or like the Burj Khalifa in Dubai – that was really unusual for that time,” says Robert Bork at the University of Iowa, who were not involved in the review. “You can compare it to the moonshot in the 1960s, and you can compare it to some of the big high-tech initiatives today.”

Notre Dame was the tallest building built when the project first began in medieval Paris in the 1160s. Examination of the cathedral during its ongoing renovation is allowed Maxime L’Héritier at Paris 8 University Vincennes-Saint-Denis in France and his colleagues to estimate that the building has thousands of staples from the floors to the upper walls.

“The fact that the framework was burned made some staples that could not be seen before appeared to us,” said L’Héritier. He described each staple as being about 50 centimeters long and weighing between 2 and 4 kilograms.

A closer examination of the 12 staples showed that they were used in the earliest stages of the cathedral’s construction, according to the researchers. They carried out radiocarbon dating analysis on samples of material taken from staples – each sample is an alloy of carbon and iron – by melting the iron to leave the carbon that came from the charcoal used in medieval ironworking furnace.

The use of iron to strengthen the building’s stones and other features — such as the iron connections of the stained glass windows — was key to creating the Gothic style of the cathedral’s architecture, Bork said. Unlike the blockier stone architecture of the Roman era, medieval builders of Gothic architecture took advantage of such iron innovation to create structures that appeared lighter and more elaborate.

“Compared to other cathedrals, such as Reims, the structure of Notre Dame in Paris is light and elegant,” said Jennifer Feltman at the University of Alabama, who were not involved in the review. “This study confirms that the use of iron made possible lighter structures in Paris and thus the use of this material was important in the design of the first Gothic architect of Notre Dame.”

The team has also begun to compare the elemental composition of different iron staples to see if the iron was produced at specific ironmaking sites – several sites were within a day’s walk of in Paris, says L’Héritier. This archaeological sleuthing process involves using lasers to crush iron samples so that they can be subjected to analysis by mass spectrometer, which allows for chemical signature comparison.

Analysis of the current strength of steel staples will even provide information to modern architects on how to reuse undamaged steel staples in rebuilding Notre Dame Cathedral to its former glory. “Now is not the time of diagnosis – it is the time of restoration,” said L’Héritier.