Notre Dame's iconic spire being rebuilt 'as it was' ahead of 2024 reopening

A team in northeastern France is busy rebuilding Notre Dame's famous spire, with construction ramping up ahead of next year's reopening.

With the cathedral's grand reopening to the public set for Dec. 8, 2024 at 11:15​ a.m.​, the first step in the restoration of the cathedral's spire is underway in Briey, a city in northeastern France.

The collapse of this iconic part of the Paris landmark in a 2019 fire left an indelible mark on the minds of millions around the world.

The stakes are high as the reconstruction of the spire relies on the success of a very rare operation which has not been repeated since 1842.

The crux of this project is to build the stool, located on the lower bottom of the structure, on top of which the spire will stand at almost 100 meters high.

"This is a critical operation," General Georgelin said, telling ABC News the reconstruction team is "now on track to have the spire finished in December 2024."

Underway since last autumn, the rebuilding process has been years in the making, according to Rémi Fromont, chief architect of Historical Monuments, who coordinates the work and rescue of Notre Dame.

The first challenge was to understand how this technical achievement of its time was made possible in order "to rebuild as well as it was."

Since last autumn, a team of 40 carpenters has been at work selecting and shaping the blocks of oak that made the final 110 pieces composing the stool.

Carpenter Paul Poulet, 27, who started his career at age 15, is one of them.

"For me, working on this project is really interesting," he said, adding he is "really proud" to be part of the efforts to rebuild Notre Dame.

Finding the best oak and artisans with the know-how needed was another complex task.

"We are very lucky in France because we have excellent carpenters" who "are still able to work as the carpenters worked in the 19th century," Fromont told ABC News.

Now, these artisans have the tough mission to fine tune the last details of this operation by making sure all the wood pieces fit perfectly, and then disassembling them without damage.

In mid-April, the stool will travel to Paris, where it will be reassembled again, with the help of an additional 20 carpenters.

"All these operations are very, very delicate," and will take "more or less 3 or 4 weeks," the architect said. The wood and the structure will be the most vulnerable so "we have to be just perfect."

By the summer, onlookers will get a first glimpse of the scaffolding at the crossing of the cathedral's transept, which will progressively grow to reach a height of 100 meters, as the progress on the restoration of the spire moves forward.