Years? Decades? Uncertainty over time needed to rebuild Notre-Dame

Rebuilding the Notre-Dame Cathedral in Paris could take decades after it was gutted by a fire, experts warned Tuesday, even as its top priest expressed hope he could celebrate mass there within years.
Parisians and people around the world watched in horror on Monday as flames ripped through the roof of the beloved 850-year-old Gothic cathedral, causing the spire and most of the vaulted roof to collapse.
"We will rebuild Notre-Dame together," French President Emmanuel Macron vowed after assessing the damage, declaring that the disfigured cathedral had been spared "the worst".

France has experience of reconstructing cathedrals, including one in Reims that was severely damaged by shelling during World War I and another in Nantes that was gutted by fire in 1972.
Asked how long the rebuild could last, Eric Fischer, head of the foundation in charge of restoring the 1,000-year-old Strasbourg cathedral, which recently underwent a three-year facelift, said: "I'd say decades."

"The damage will be significant. But we are lucky in France to still have a network of excellent heritage restoration companies, whether small-time artisans or bigger groups," he told AFP.
Fischer said the ability to rebuild the colossal cathedral in a manner that respects its original form and character would depend on the plans, diagrams and other materials available to the architects.
They would need "a maximum of historical data or more recent data gathered with modern technology such as 3D scans" of the kind used in the restoration of the Strasbourg cathedral, he said.

'Not in my lifetime'
The French government's representative for heritage, Stephane Bern, said that money would not be the problem.
Within hours, pledges of donations amounting to nearly 700 million euros ($790 million) had flooded in from some of France's richest families and companies and foreign governments were lining up with offers of help.

Bern, a 55-year-old TV presenter famous for his programmes on medieval France, said he feared it would not reopen in his lifetime.
"It will be rebuilt for future generations," he said.
A symbol of Paris for close to a millenium, serving as a sanctuary for the hero in Victor Hugo's classic novel "The Hunchback of Notre-Dame", the towering house of worship has been in the wars before.
During the French Revolution its treasures were plundered and the figures of kings carved into the stone above its entrance doors defaced.

Deemed unstable the spire was dismantled in 1792 and the cathedral fell into a state of disrepair until the mid-19th century when architect Eugene Viollet-le-Duc gave the famed structure a major makeover.
But the intricate wooden oak frame that held up the roof, the so-called "forest", had stood the test of time since its construction in 1220-1240 -- until being consumed by Monday's inferno.
For carpenters, "it's a bit as if the Mona Lisa went up in smoke," Thomas Buechi, head of Charpente Concept which specialises in timber frames, told AFP.
Recreating it will be the trickiest part of the restoration, experts said.

France's top producer of oak said he was worried the country did not have enough of the precious timber for the job.
Sylvain Charlois estimated that around 1,300 oak trees had been used in the construction of the original roof.
"To constitute a big enough stock of oak logs of that quality will take several years," he said.

Tighter deadline needed?
Francois Jeanneau, one of the 40 architects in charge of state monuments, suggested that Paris draw on the example of Nantes cathedral and build a new "forest" of reinforced concrete.
"The un-initiated can barely tell the difference," he told Le Parisien newspaper.

Despite the longer forecasts of decades of work, the rector of Notre-Dame, Monsignor Patrick Chauvet, said he was hopeful of being back behind the pulpit before he retired.
"I'm 67 now and if all goes well, even if it takes 10 years, I will be 77 and still able to do it," he told France Inter radio.
Jack Lang, who served as a hugely prominent culture minister under late president Francois Mitterrand, called talk of a decade-long restoration programme "a joke".
"We have to give ourselves a tighter deadline, like we have done in the past on major projects."

'Legendary' Notre-Dame roof astounded Middle Ages, says carpenter

The charred roof of the Notre-Dame Cathedral in Paris was once a legend that "astounded the Middle Ages" and still fascinates master carpenters, Thomas Buechi of the Charpente Concept group told AFP.

What does the roof represent for master carpenters?
It is possibly one of the greatest masterpieces for French master carpenters. For a painter it would have been a bit as if the Mona Lisa went up in smoke.

The framework (known as "the forest") was mythical, it was a legend for several reasons. It was so complex that it astounded the Middle Ages.

First of all, it took 50 years to prepare the timber. They began cutting the trees, around 1,500, sometime around the year 1200.

These were laid for a year with the top turned to the North to align them with the energy of the earth.

The bark was then removed and they were immersed in a swamp for 25 years to preserve the wood from fungus and insects.

Around 1225, the wood was removed from the water and the trunks were sawed into beams and allowed to dry for another 25 years.

Given average lifespans at the time, it meant that most of those who cut down the trees never saw the roof structure.

Who erected the more recent spire that collapsed?
The French revolution left the cathedral in ruins. In the middle of the 19th century the decision to redo the spire was made.

In addition to the architect, Eugene Viollet-Le-Duc, there was a key figure who has been forgotten, Henri Georges, a master carpenter.

He was a master of "operative geometry" and his nickname was "Angevin, the child genius".

When I saw the spire burn and fall yesterday, he was the one I thought of.

Which challenges face those charged with the reconstruction?
We do not know yet how much the stone has suffered. That everything is still standing is a miracle.

For the roof structure, either they will reconstruct it like before, or do something completely different.

Rebuilding this masterpiece would involve all professionals in the wood sector. I think there will be a massive mobilisation.

They should not do as they did for the Chartres Cathedral, where the roof burned in the 19th century and was replaced by a metal framework.

In France there are plenty of oaks, the wood will not be a problem. They could use old trees and leave more space for young ones to grow.

In the Troncais forest (in central France) there are oak trees that are several hundred years old.

They could never prepare the wood the way it was done in 1200. But today's technology would allow work to proceed faster. You could foresee starting to receive beams two years from now, and replace the roof structure in the next five years.