Vault replica: Notre Dame chief architect visits unique laboratory

The Chair of Building Technology History at the Faculty of Architecture, Civil Engineering and Urban Planning offers researchers something that is unrivalled - at least in Europe. A stereotomy laboratory (stereotomy: the science of cutting stone) in which parts of historical buildings are experimentally reconstructed. The purpose behind this is to reconstruct how things were once done, as the literature on the subject is of little help. This was also the case with the vaults of Notre-Dame, which were partially destroyed in the major fire in 2019.

Prof. Dr.-Ing. David Wendland, head of the chair, explains: "We reconstructed part of the Notre-Dame vaults in our stereotomy laboratory because we wanted to understand how the geometry works. The stonework is perfect, but also very complex. In our laboratory, which is unique in Europe, we experimented with how the master builders might have proceeded. This enabled us to reconstruct the vaults."

Pascal Prunet, one of the cathedral's three chief architects, was able to see for himself just how successful this was. Before his evening lecture on the restoration at the BTU, he visited the laboratory to inspect the replica. He praised the important impetus provided by the research and teaching of architectural history at the BTU and spoke about the challenges involved in restoring the vaults of Notre-Dame.

"One difficulty was that the stones had shrunk by three centimetres due to the heat and were mixed with the melted steel of the metal scaffolding of the building site, which was supported in the cathedral together with the spire. We initially spent months trying to work out how to restore it true to the original. And we didn't know at the beginning whether the building could remain as it was."

It could - and in December 2024, the reopening of the faithfully restored World Heritage Site was celebrated. Prof. Wendland will continue to work on its vaults in the future, as there are still some adjustments planned for the replica in the stereotomy laboratory.