Notre-Dame May Have Been the First Gothic Cathedral to Widely Rely on Iron Staples in Its Stonework

Large iron staples have been found in Notre-Dame Cathedral’s stonework among the walls, columns, and tribunes. A recent study in the peer-reviewed journal Plos One revealed the find—and suggested that because of the staples, Notre-Dame may be even more significant than experts even realized.

Researchers used a radiocarbon-based dating method to determine that the iron staples were from the 800-year-old monument’s original construction. Historians have long thought that the metal pieces were added during renovations in the 18th and 19th centuries.

This discovery makes Notre-Dame “the first known Gothic cathedral where iron was massively used as a proper construction material to bind stones,” the researchers note. “Whereas other buildings used wooden tie rods stretched between the arches… the first master builder of Notre-Dame de Paris made the bold choice of a system using a more durable material that could be more easily concealed.”

With permission, the team removed some of the staples to examine them more closely and found that they weigh between four-and-a-half and nine pounds each and are approximately 8 to 20 inches in length. Additionally, the researchers found “that several pieces of iron, sometimes from different provenances, were welded together to form each staple.”

It is unclear why different metals were used, but this may reflect the overall duration of the project, which took more than a half-century to complete beginning in 1163.

Following a devastating fire that destroyed parts of the cathedral in 2019, experts have been able to learn more about the building’s construction. During the restoration efforts, previously hidden objects, such as artworks and sarcophaguses, have been discovered. The restoration project is expected to finish in 2024.