NEW YORK — The catastrophic Holy Week fire that ravaged Notre Dame Cathedral in Paris completely destroyed the roof and center spire, although its famous facade of the centuries-old gothic house of worship were spared and remains intact as did the lower part of the church.

As investigators continue to sift through the damage — which includes three massive holes in its vaulted ceiling — in an effort to pinpoint the cause of the inferno, French officials and architects are working to determine how much money and time it will take to restore Notre Dame to its previous glory.

“We have so much to rebuild,” French President Emmanual Macron said Tuesday in a televised speech from Paris. “We will rebuild Notre Dame Cathedral even more beautifully. We can do it, and once again, we will mobilize.”

French officials confirmed on Tuesday, a day after the blaze, that the cathedral is structurally sound. Macron vowed that the landmark church, a symbol of Paris and Roman Catholicism for the past 800 years, will enact an ambitious timetable of just five years to get the project completed.

The investigation into the cause of the blaze remains under investigation. Despite a spate of vandalism at French churches over the past few months, authorities do not believe this latest incident to be arson.  

How long can it take to rebuild?

French officials said an international effort would be needed to pay for the reconstruction. Although Macron said rebuilding would be completed by 2024 (with one estimate saying it could cost $8 billion), some experts said the cathedral’s full renovation could take up to 15 years. In terms of money raised, the billionaire Pinault family has pledged $113 million, as did the French energy company Total and cosmetics giant L’Oreal. The family of Bernard Arnault, who own luxury goods group LVMH Moet Hennessy Louis Vuitton, has planned to donate $225 million. Donations are coming in from all over the world, including $100,000 from Notre Dame University.

It’s worth noting that the cathedral was not insured. Instead, it is owned by the French government (they own all religious buildings built before 1905) and they are on the hook for coming up with the funds to pay for its reconstruction. As for what those funds would specifically target, architects said three main areas of the cathedral need to be rebuilt: the spire, the transept and the vault of the north transept. Most of the wooden roof beams were destroyed and sections of the concrete vaulting that holds up the roof collapsed as a result of the blaze.

Asked how long a project of this magnitude could take, Dr. Carolyn Malone, a professor of Medieval Art and Archaeology at the University of Southern California, was optimistic and agreed with Macron’s timeline.

“Possibly in five years, if the structure is solid,” she said.

What needs to happen next?

While it’s true that many relics and other works of art were saved from the flames (including a crown of thorns believed to have been worn by Jesus and the building’s iconic rose windows), the cathedral’s original roof was unique.

The wood used to build the ornate roof came from oak trees dating back to the 1200s. These beams are the trees of what’s known as the “forest” of the still-smoldering cathedral, an intricate network of some 1,300 trees that made up the frame.

Frederic Letoffe, who heads the group of French companies for the Restoration of Historic Monuments, said the primary aim will be to first secure the structure.

“This will require a lot of work since — beyond shoring and reinforcement — it will be necessary to build a scaffolding with an umbrella to be able to cover the entire roof that went missing, to ensure protection against weathering,” he said.

Peter Riddington, an architect at Donald Install Associates who worked on the restoration of Windsor Castle after it was damaged by a fire in 1992, agreed with that assessment.

“There are three key matters to be addressed: Firstly, the surviving parts of the building must be secured and anything that is likely to be able to be repaired in situ is protected. Secondly, there needs to be an archaeological sift of the debris to retrieve any material that might  be helpful in the restoration project. And there will need to be a temporary roof installed to allow the building to start drying out and to protect the surviving fabric.”

Where will the materials come from?

A $6.8 million renovation was already underway at the Parisian cathedral before the fire occurred. The cathedral has undergone a series of reconstructions over the centuries. The cathedral was remodeled in the 17th and 18th centuries. In 1786, the original spire was removed. The spire that collapsed in Monday’s fire had been built in 1859.

Writing in the New York Post, art historian Elizabeth Lev said:

“The cathedral was dubbed ‘the forest’ since it took 50 acres of forest to build the enormous roof. Timbers and beams hidden under the high ribbed vaults continued the effect of loftiness in the church, hidden, until today. The forest fire that ravaged the cathedral of Notre Dame burnt away dense layers of history, good, bad, ugly and beautiful piled up as ashes on the ground.”

The French timber industry said it is offering to help. The Fondation Fransylva, a group that represents private timber growers in France, has asked its members to offer up an oak tree for the cathedral.

“Loggers want Notre-Dame re-constructed with French oak trees in keeping with the same traditions and good quality of the first builders,” the group said on its website.

In an effort not to have a repeat of Monday’s disaster, Malone said officials should consider other materials when building the roof.

“I wouldn't take the path of wood for safety’s sake,” she said.

Indeed, the wood needed could be an issue.

“If the roof is to be rebuilt in oak, as it most certainly would have been previously, then this could slow the entire process of restoration down, there is much, much less oak available now than in previous times,” Riddington said. “This may indeed be the critical element in determining the duration of the project. However, it may be decided that alternative materials may be acceptable for hidden elements — such as steel — and this could certainly reduce the time needed.”

Can technology be of help?

Over the last decade, Andrew Tallon, an architectural historian, worked with laser scanners to capture both the cathedral’s interior and exterior with the use of 3D imaging. Tallon, who died in 2018 at the age of 49, explained to National Geographic how laser scanners could be used to deconstruct Gothic architecture.

“Every building moves,” he told the magazine in 2015. “It heaves itself out of shape when foundations move, when the sun heats up on one side.”

Those movements, Tallon believed, can reveal the original design and the decisions the master builder had to make at the time. It is very possible that these scans could come in handy when it comes to reconstructing the church.  

A series of cutting-edge technologies — such as the use of robots — could be used to go places people cannot safely go to replicate detailed artifacts destroyed in the fire.

Who can rebuild the cathedral?

There are still many skilled laborers and craftspeople — such as masons and carpenters — who can work on such a massive project. 

John David, a master mason with over 45 years of experience, worked on the restoration of York Minster, the largest cathedral in Great Britain. That gothic church was heavily damaged in 1984 by a fire.

“What I’ve heard a number of times today is people saying, ‘we can't do this anymore, we haven't got the craftspeople to do it.’ We have,” he told CNN. “We have plenty, and we have plenty of people who can train others.”

Riddington said the restoration of York Minster and Windsor Castle could serve as a potential template for future work at Notre Dame.

“There have been many church-cathedral fires over the centuries, but few perhaps which have affected a nation in the way that Notre Dame has affected the French… I’m sure these will offer both consolation and inspiration to those tasked with restoring the cathedral,” Riddington said. “No two projects are exactly the same and one of the issues for Notre Dame is its sheer size and the need for so many craftspeople and materials. I can’t think of a precedent for the scale that this project will be.”