Thousands of iron staples were used to build Notre-Dame Cathedral in Paris, study finds

When Notre-Dame Cathedral in Paris was constructed in the 12th century, the builders made extensive use of iron to bind stones together. The 2019 fire that significantly damaged the cathedral enabled analyses leading to this discovery, which has been published in PLOS ONE.

At the time of its construction in the mid-12th century, Notre-Dame was the tallest building ever erected, reaching a height of 32 meters. Previous research suggests that this record was made possible by combining a number of architectural innovations. However, despite extensive use of iron reinforcements in more recent cathedrals and in efforts to restore old buildings, it has been unclear what role iron might have played in Notre-Dame’s initial construction.

Staple from the restoration site of Notre-Dame de Paris, after cutting to prepare a metallographic analysis. Photo © Cyril FRESILLON / IRAMAT / NIMBE / ArScAn / CEA / Notre-Dame de Paris Scientific Site / Ministry of Culture / CNRS

Now, the 2019 fire and subsequent restoration have allowed a team led by Maxime L’Héritier of Université Paris 8 to access previously concealed parts of Notre-Dame that hold clues to the possible use of iron in its construction. The researchers obtained samples of material from 12 iron staples used to bind stones together in different parts of the building, including the tribunes, nave aisles, and upper walls. They applied radiocarbon dating as well as microscopic, chemical, and architectural analyses to better understand the staples.

These analyses suggest that iron staples were indeed used in the earliest phases of the construction of Notre-Dame in the 1160s, making it the first building of its type to have relied on iron staples throughout its structure.


The researchers explain:

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 medieval builders used several thousand of iron staples throughout its construction.

In combination with other archaeological and historical knowledge for that time period, the analyses also provide information that could help deepen understanding of the iron trade, circulation, and forging in 12th and 13th century Paris. For instance, many of the staples appear to have been forged by welding together pieces of iron obtained from a number of different supply sources.

The researchers note that further analyses of Notre-Dame samples and a comprehensive database of historical iron producers in the region are needed to confirm and expand on their novel findings regarding the medieval Parisian iron market.

The article, “Notre-Dame de Paris: The first iron lady? Archaeometallurgical study and dating of the Parisian cathedral iron reinforcements,” by Maxime L’Héritier, Aurélia Azéma, Delphine Syvilay, Emmanuelle Delqué-Kolic, Lucile Beck, Ivan Guillot, Mathilde Bernard and Philippe Dillmann, appears in PLOS ONE. Click here to read it.


Top Image: Photo by Ninara / Flickr