https://www.wsj.com/graphics/notre-dame-fix/?mod=article_inline&mod=hp_lead_pos10
Almost a year after last April’s devastating fire, Notre Dame is still in a fragile state. Workers had been racing to stabilize the 800-year-old structure before the effort was suspended indefinitely last month due to the coronavirus pandemic, putting the project in even greater jeopardy.
The fire destroyed a section of the cathedral that acted as the linchpin of its medieval design: its roof and central spire. Like a ballast, the spire and roof pushed downward and outward on Notre Dame’s limestone walls, countering the inward pressure generated by the cathedral’s flying buttresses and massive facade.
Without the spire and roof in place, the limestone walls of Notre Dame’s nave are at risk of tilting inward and its vaulted ceiling can buckle. Already, about 15% of the ceiling collapsed during the fire and over the summer. Notre Dame’s famous flying buttresses are still pushing against the walls, but without the counterweight of the roof and spire, they are at risk of collapsing if the vaults give way. The gables are also at risk because they are no longer supported by the roof. The north gable nearly collapsed during the fire.
Water used to douse the flames created fissures in the massive stones that arc above Notre Dame’s nave, and seeped into the joints and mortar, leading to crumbling. Some of that water may have frozen over the winter, potentially weakening the structure further. The cathedral is covered in lead that melted from the roof and spire, which were made of several hundred tons of the toxic metal. Workers doing cleanup wear hazmat suits to prevent lead contamination and shower each time they leave the site. Back outside, charred scaffolding looms at the cathedral’s most vulnerable point, where the spire once rose. It had been erected for restoration efforts before the fire. Now distorted and highly unstable, it has been swaying in the wind and rain. Its collapse would be catastrophic.