Seven years before Notre Dame's devastating cathedral fire, then-architecture-student Rémi Fromont was pursuing a DSA* at the Ecole de Chaillot, a prestigious architectural heritage and preservation school in Paris. As part of his coursework, Fromont was studying and cataloging medieval structures, including Notre Dame's cathedral. Fromont and fellow student Cédric Trentesaux spent an entire year precisely measuring the cathedral's charpente, the timber-framed roof structure, and got the entire thing into CAD.

Eventually preparation met opportunity, helped along by tragedy. In 2019 the cathedral's charpente went up in smoke, and suddenly one of Fromont's hard drives became extremely valuable. Here in 2023, thanks to his crucial project, Fromont is now the lead architect in charge of the charpente's restoration.

The original charpente required so many timbers to build that it was nicknamed "the forest." "Working inside the massive wooden structure was extremely impressive," Fromont told NPR, describing his student project. "You're in the sky but completely in the dark, so you discovered 'the forest' with flashlight and headlamps, never entirely seeing the whole thing."

Fromont has three degrees in Architecture, but while he recorded the position and disposition of every timber, crafting and assembling them requires a different discipline altogether. That task has fallen to Ateliers Perrault, a 260-year-old historical architecture restoration firm that won the bid to rebuild the charpente—using ancient methods and old-school tools.

Ateliers Perrault employs over 160 highly-trained tradespeople that have graduated from the top schools in their fields, whether working wood or iron. It is the woodworkers, specifically the ones with ancient timber-framing skills, that are tackling the charpente.

­­And while the company has their own sawmill, the reverence commanded by Notre Dame means the timbers won't be going through it; instead they're being "taken from the round tree to a square timber all by hand, all with axes" according to a tradesperson on the job. The company has forged some 60 axes of different sizes specifically for the purpose.

"These axes leave a magnificent mark on these beams," says Ateliers Perrault carpenter Edouard Cortes. "The same medieval mark found on the beams from Notre Dame."

But if "the forest" will eventually be back where it was, in darkness, and no one can see the marks, why bother building it the old way?

"A cathedral is a structural ensemble that's very complex, and as soon as you change one little thing, one parameter, it impacts everywhere else in the cathedral," Fromont explains. "So reconstructing it exactly the same way is also a precaution. It worked very well for 800 years. So we know if we build it back the same way we won't risk damaging the cathedral by trying something new."

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*The DSA is a French post-Masters degree that stands for "Diplôme de Spécialisation et d'Approfondissement" (Diploma of Specialization and Deepening). Fromont earned his DSA in Architecture & Heritage.