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Iron staples inside the walls of Notre-Dame

Iron staples used to support the stone blocks weighed between 2 and 4 kg

L’Héritier, M. et al. PLOS ONE. 2023

While the roof of the Notre-Dame Cathedral in Paris was being rebuilt after it was destroyed by a fire in April 2019, archaeologists examined 12 iron clamps used to support the stone blocks of the walls, columns, and tribunes (balconies), each weighing between 2 and 4 kilograms (kg) and measuring 20 to 50 centimeters (cm) in length. It is estimated that 300–400 of these staples can be found throughout the building. A radiocarbon-based dating method indicated that six clamps were used in the cathedral’s original construction in 1163 and not during renovations in the eighteenth and nineteenth centuries. The conclusions suggest Notre-Dame was the first cathedral to use iron extensively, while others from the same era used wooden arches. Built over more than half a century, the church was once the tallest building in the world at 32 m high. The nave is 37 m wide and 125 m long. The restoration work is projected to be completed in 2024 (PLOS ONE, March 15; Big Think, March 27).