Restoring Notre-Dame to its original state could be impossible - because France doesn’t have enough trees that measure up to the job.
Bertrand de Feydeau, vice president of preservation group Fondation du Patrimoine, told France Info radio that the wooden roof that went up in flames was built with beams more than 800 years ago from primal forests.
He said the cathedral’s roof cannot be rebuilt exactly as it was before the fire because “we don’t, at the moment, have trees on our territory of the size that were cut in the 13th century”.
He said the restoration work will have to use new technologies in order to rebuild the roof of Paris’ most-visited monument.
Peter Riddington, a consultant director with Donald Insall Associates, which oversaw the restoration of Windsor Castle following the 1992 fire, said he felt a solution would have to be found.
He added: “The history of the cathedral is so strong that to rebuild it in a form that isn’t what people understand Notre-Dame to be, what it symbolises and what they believe it to be would be a very difficult argument to win.
“There will be a lot of soul searching I think.”
While Windsor Castle was a straightforward rebuild due to the “cellular” structure of the rooms Mr Riddington said Notre Dame’s status as a place of worship - and a large one at that - presents extra challenges.
Windsor saw some 1,500 workers help rebuild and restore the castle at a cost of around £36m, 27 years ago - though both the cost and the four year project came in ahead of schedule and under budget.
He said: “I think it’s a much bigger, more difficult rebuild.
“One thing I would say though is that it is not the first cathedral fire over the years.
“The west wing at York was badly damaged in the 1980s but they do get restored.”
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French President Emmanuel Macron has already pledged to rebuild the most-visited monument in his country and has promised to bring in the best talents from around the world to do so.
Paris public prosecutor Rémy Heitz said his office was "favouring the theory of an accident", but had assigned 50 people to work on what he believed would be a "long" and "complex" investigation.
French tycoon Bernard Arnault and his luxury goods group LVMH have pledged 200 million euro (£173 million) towards the reconstruction of Notre Dame, following a reported 100 million euro (£86 million) donation from another French billionaire, Francois Pinault.