Wealthy industrialists and ordinary individuals have donated more than €600m (£520m) in less than 24 hours to help restore Notre Dame Cathedral in Paris, but experts have said reconstructing the building could take decades.

On Monday evening a blaze tore through the 850-year-old gothic cathedral, toppling its spire, destroying large parts of its vaulted roof and triggering a scramble to save its precious relics and artworks.

The French president, Emmanuel Macron, promised France would “rebuild Notre Dame together”, describing the cathedral as “our history, our literature, the epicentre of our life … The cathedral of every French person, even those who have never visited it.”

The cost of reconstruction has been estimated at hundreds of million of euros, and as donations poured in it looked as if there would be no shortage of funds. Notre Dame’s rector, Patrick Chauvet, said he hoped to celebrate mass there within a decade, but some experts predicted the project could take many times longer.

The French billionaire Bernard Arnault and his luxury goods group LVMH promised on Tuesday to donate €200m (£170m), hours after his longstanding rival François Pinault, the fashion and retail magnate, announced he was giving €100m.

The Bettencourt family, part-owners of L’Oréal, will contribute €200m, the energy group Total €100m, and the brothers Martin and Olivier Bouygues of the eponymous construction, media and telecoms firm announced a personal donation of €10m, as did an American couple, Henry and Marie-Josée Kravis.

The mayor of Paris, Anne Hidalgo, said the city would provide €50m and organise an international donors’ conference to coordinate gifts from abroad. The Île-de-France region of which Paris is a part pledged a further €10m.

Macron has said a national appeal, likely to be accompanied by tax incentives, would be launched as soon as possible, and the privately run French Heritage Foundation said its call for donations had raised €2m from individuals by midday on Tuesday.

A range of fundraising events have already been announced, including benefit matches featuring France’s World Cup football champions and a star-studded concert to be broadcast on Saturday night on French public television.

Unesco has said it will help France assess and repair the damage to the cathedral, which typically welcomes 13 million visitors a year, while Italy, Russia and Germany all offered to send restoration experts.

Eric Fischer, who heads a foundation restoring the 1,000-year-old Strasbourg Cathedral that recently underwent a three-year facelift, said he thought rebuilding Notre Dame would probably take several decades.

“The damage will be significant,” Fischer told Agence-France Presse. France was “lucky to still have a network of excellent heritage restoration companies”, he said, and the work would depend on the the plans, diagrams and other data available to them.

Some have expressed hope that detailed 3D maps of Notre Dame created in recent years by academics such the late US art historian Andrew Tallon, who used laser scanners to create a model of the building accurate to within 5mm, could help – as could similar near-perfect computer models generated for video games such as Assassin’s Creed Unity, which is set in Paris.

This video has been removed. This could be because it launched early, our rights have expired, there was a legal issue, or for another reason. Drone footage shows Notre Dame Cathedral fire damage – video

But Patrick Palem, a former chief executive of Socra, a restoration company, estimated the total length of the project at between 15 and 20 years, while Stéphane Bern, a TV presenter and the government’s heritage representative, put it at 10 to 20 years. “It will be rebuilt for future generations,” Bern said.

Notre Dame: experts assess damage after fire extinguished - live updates Read more

Much would depend on the choices made by the architects, other experts said. François Janneau, one of 40 state architects responsible for France’s major monuments, said Nantes Cathedral, devastated by fire in 1972, was partly reopened three years later, though its timber roof beams were replaced with concrete.

Amid calls for the “forest” of wooden beams that made up the gutted roof frame of Notre Dame’s nave to be replaced like for like, Sylvain Charlois, of the Charlois group, France’s biggest producer of oak, said he was worried about available stocks.

About 1,300 oak trees were used to construct Notre Dame’s roof, Charlois said. “To constitute a big enough stock of oak logs of that quality will take several years.” He called on France’s timber merchants to make donations in kind.

Jack Lang, who was culture minister under François Mitterrand, said talk of a decade or more of rebuilding was “a joke. We have to do the same thing as Strasbourg here, not in 10-15 years but three years. You have to set a short deadline.”

• The graphic in this article was amended on 18 April 2019. An earlier version referred to the 93-metre spire; it reached a height of 93 metres from the ground. It also erroneously stated that some of the wooden roof beams were 110 metres long.