Tests were underway on Friday to assess the impact of the searing summer heat on the fire ravaged structure of Notre-Dame cathedral in Paris.
The 850-year-old building was devastated in April by an inferno that gutted the ceiling and sent the cathedral’s spire crashing through a part of the ceiling.
“I am very worried about the heatwave,” said Philippe Villeneuve, who is the chief architect of the cathedral's restoration.
“What I fear is that the joints or the masonry, as they dry, lose their coherence, their cohesion and their structural qualities and that all of sudden, the vault gives way.”
Temperatures hit a record 42°C (107.6°F) in Paris on Thursday. The capital and 20 departments across northern France were placed on high alert because of the heatwave.
The vaults have been stable since firefighters extinguished the flames but Villeneuve warned: “They could still collapse at any moment.”
Buildings conservationists says the danger in a heatwave stems from the water trapped inside the walls and vaults drying faster than anticipated.
The salts in the water crystallize and expand and then erode the mortar as well as the stones of the walls and the vaults.
Temperatures in Paris were due to reach a maximum of 30° on Friday with the likelihood of rain in the evening.
