For God and for France – Rebuilding Notre Dame

President Emmanuel Macron and his wife Brigitte tour the reconstruction last week, marking the 4-year anniversary of the fire. YouTube.

Visiting Notre Dame 4 years after the fire was President Emmanuel Macron and his wife Brigitte. They were checking on its progress. Macron, overcome by the loss of a national treasure and a sense of duty, had declared days after the fire that not only would Notre Dame be rebuilt in 5 years, but it would also be more beautiful.

Notre Dame’s chief architect said it would be done for “God and for France.”

Is Paris burning? Notre Dame Cathedral survived Nazi occupation only to be gutted by fire on April 15, 2019. Stock photo.

For the French, April 15, 2019, is a day never to be forgotten. On that Monday, at 6:20 p.m. local time, smoke was seen coming from the top of Notre Dame Cathedral. It was Holy Week, the day after Palm Sunday, and the holiest shrine in Paris was burning. At 7:05 p.m., everyone in Paris watched in shock and horror as the cathedral’s 96-meter-tall spire, engulfed in flames, toppled over, crashing through the roof, leaving a gaping hole and falling to the ground with the blast of a truck bomb.

Rushing to save Notre Dame were hundreds of firefighters, not knowing if they’d ever come out. They were to emerge as heroes, saving Notre Dame from total collapse and ruin.

Fire Makes It Rain

Saying that Notre Dame would be rebuilt in 5 years may been the right thing for an elected leader to say, but our lady (English for Notre Dame) was in bad shape before the fire and was very much showing her age. “On the face of this aged queen of our cathedrals, by the side of a wrinkle, one always finds a scar,” wrote Victor Hugo in “The Hunchback of Notre Dame,” published in 1831. A 2017 report by TIME magazine found her in “dire need of repair.”

“The damage can only accelerate,” said Andrew Tallon, an associate professor of art at Vassar College and an expert on Gothic architecture. (Tallon died 6 months before the fire but played a big part in the story of the cathedral’s reconstruction). “The flying buttresses, if they are not in place, the choir could come down. The more you wait, the more you need to take down and replace.”

Notre Dame was slowly succumbing to the ravages of time, its façade crumbling. As its famous gargoyles’ faces were “worn away like the face of Voldemort,” the secular government and the Catholic church argued about who would pay for the extensive repairs needed.

The 2019 catastrophe changed everything. Over a billion dollars has poured in from private donors. Dassault Systèmes’ CEO Bernard Charles pledged support to help rebuild Notre Dame. So did a video game maker Ubisoft, pledging €500,000. The Paris-based company had digitized Notre Dame for its Assassins Creed game.

Nicolas Mangon, VP of Autodesk’s AEC strategy, a native of France who had studied architecture just blocks away from Notre Dame (École Spéciale des Travaux Publics, ESTP) and CEO Andrew Anagnost pledged software and a team of volunteer staff to help create two BIM models of the cathedral—one before the fire and one after.

Everyone agreed that Notre Dame would now be completely rebuilt.

Promises, however, are easier made than kept. To remake parts of the old cathedral that was lost to fire, the timber beams, frescoes and statues required something that could be copied. But reliable documentation of all the architectural details of Notre Dame is very spotty: overdone in well-traveled and treasured areas and nonexistent in others, such as many areas that are now missing or burnt beyond recognition.

Enter the Incredibly Talented Dr. Tallon

Image: from LiDAR model by Andrew Tallon (Vassar College/Columbia University)

As if by miracle, Andrew Tallon, a man who was obsessed with Gothic architecture, had scanned the entire cathedral, floor to ceiling, inside and out, with LiDAR and photographs. His scan showed details with such fidelity that it was being used to convince 23 European countries to do similar scans of all their heritage buildings should—perish the thought—some sort of catastrophe befall them.

Andrew Tallon, the man responsible for providing the extraordinary detail of Notre Dame with LiDAR scans. Image: National Geographic.

That there was accurate data available for a BIM model was serendipity, to say the least. The accurate data, the result of scans and photos, was the work of one man, a labor of love and years of persistence by a doomed professor of art, Dr. Andrew Tallon. Tallon, who scanned 45 Gothic buildings, culminating with Notre Dame, was to succumb to brain cancer 6 months before the fire, never to realize how his work would be indispensable in the reconstruction of a national treasure.

A native of Belgium, the young Tallon was in Paris while his mother studied for her dissertation. They would visit Notre Dame often. He would fill a guidebook with notes and his head with questions, chief among them: how did they build this?

It was a question that gnawed at him into adulthood and through various pursuits. He studied music for a bachelor’s degree at Princeton while sneaking into classes about the structure of Gothic buildings taught by an engineer. He went to Sorbonne for a master’s degree in medieval music, then went off to New York to start a music studio, then applied for life as a monk in California. Turned down, he went back to New York to get a PhD from Columbia. That led to a tenured position at Vassar, where he taught art and architecture. Throughout the twists and turns, however, his mind was never far from Notre Dame.

Tallon was convinced that accurate measurement of every aspect of the cathedral would be the key to unraveling its secrets. Methods of measurement when Notre Dame was built were cubits and had scarcely improved since.

“You can’t hang from a vault and measure it by hand,” said Michael Davis, an art historian at Mount Holyoke College who spent nine weeks measuring two churches just that way, quoted in National Geographic.

Tallon, after a protracted study of explanations of how Notre Dame was built, said, “They got a lot of things wrong.”

For example, there were accounts of Notre Dame’s now-famous flying buttresses being added after the cathedral was built to shore up the walls. Tallon concluded, based on his scans, that there was no movement of the upper parts of the walls, so the buttresses must have been there from the beginning.

At the forefront of laser scanning technology being applied to Gothic architecture, Tallon had to improvise and take big risks. The scans of Notre Dame were taken from 50 locations, some of them precarious ones. Seeing one photo of Tallon “stepping into the void” to go around his tripod on a ledge 80 feet above the ground made his wife Marie threaten to smash his camera. Tallon’s camera was omnidirectional and used from the same position as the scanner. He was able to manually register the monochrome points of the scanner with the color pixels of the camera to make what is effectively an undistorted 3D photograph. Tallon claimed an accuracy of 5 mm.

Tallon took his scanner all over Europe, scanning 45 Gothic buildings. He was granted permission to scan Notre Dame in 2015, the same year he was diagnosed with terminal brain cancer. He died on November 18, 2018. He was 49 years old.

References

“Notre Dame Cathedral Is Crumbling. Who Will Help Save It?” Vivienne Vault, TIME, July 27, 2017.

“The Resurrection of Notre Dame,” 60 Minutes, April 9, 2023.

“Historian Uses Lasers to Unlock Mysteries of Gothic Cathedrals,” National Geographic, June 22, 2015.

“Professor Who Scanned All of Notre Dame Died Months before the Fire,” Barbie Latza Nadeau, April 20, 2019