Notre Dame: How the Restoration Should Be Done

Restoring Notre Dame de Paris is a marathon began a little less than five years ago, and which should come to a close within a few months. After having rebuilt the two arms of the transept and the spire, the carpenters are now setting to work on reconstructing the nave. A Titan task, which has also benefited from several decisive strokes of Providence.

It is a feat which could have never seen the light of day: the day after the fire, debate was lively between architects, among those who wanted to leave the structure as it was to transform it into a place of commemoration, or on the contrary to make a more modern and light one.

Ultimately, reason, likely enlightened by grace, prevailed: "Not restoring the framework identically would have degraded the heritage value of the cathedral," highlights Rémi Fromont, chief architect of historic monuments. 

But this identical restoration could not have been done 50 years earlier. If modernity sometimes has its perverse effects, technological advances are not all bad: they have made it possible to fill in the gaps in architects' and archeologists' knowledge and observations about the framework. 

Not to mention another helping hand from Providence. In 2015, four years before the terrible fire, Rémi Fromont began to establish a meticulous architectural survey of the framework he admired, and which he did not imagine would soon go up in smoke. "This saved the structure of Notre Dame de Paris," Frédéric Epaud, director of research at the French National Center for Scientific Research (CNRS), laconically stated. 

It remained to retrace the different stages of the construction of the cathedral, a construction which lasted close to two centuries, taking into account that the techniques used evolved over generations of carpenters through whose hands the wood passed. It is a Titan task, for two pieces of wood side by side removed from the structure could be extremely different. 

In fact, in the Middle Ages, particularly young (and thin) oaks were used, cut by axe to respect the direction of the fibers, in a green wood which allows both great flexibility and great resistance. But the trees of the 19th century, used by Viollet-le-Duc to construct the spire, are generally older (and more massive), sometimes dried and preferably cut by saw. 

There was no question of ignoring Viollet-le-Duc's restorations: "His spire, since its construction, has been considered an absolute masterpiece. It is one of the most complex solid wood frameworks of the 19th century, and the most remarkable by its design, the complexity of its assemblies and its layout, and its dimensions," Rémi Fromont insists. 

Contrary to popular belief, "Viollet-le-Duc's work is extremely respectful of the ancient material," adds the architect, who explains that his illustrious predecessor endeavored to restore the building while respecting its Gothic style. Rather than replacing them, certain medieval wood pieces were thus taken down and reused in the restorations. 

Let us add to this series of expertise the contribution of the professor of medieval art at Vassar College (New York), Andrew Tallon, who had developed--also before the fire--a map of the framework, using a method based on laser scanning, allowing distances to be measured with precision down to the millimeter. 

A great amount of data was synthesized in the immense digital model produced by Livio De Luca's team, which served as a basis for architects to carry out the identical restoration. 

A restoration which will perhaps make the poet a liar: 

Notre Dame is very old: nonetheless, perhaps

It will see buried the Paris that saw it born; 

But, in some thousand years, Time will consume 

This heavy carcass, like a wolf an ox—

Will twist its iron sinews, and then, with a gnawing tooth, 

Dolefully eat away at its old bones of rock! 

— Gérard de Nerval: Notre-Dame de Paris, Odelettes (1834).