And they rebuilt it with all the lead that posed problem when it burned.
Lesson not learned. Go figure.
Lesson not learned. Go figure.
I was very surprised to learn this is indeed true.
"As the flames engulfed the cathedral, a whopping 400 tonnes of lead from the roof and spire went up in smoke, according to French authorities."
"The decision to rebuild the spire and roof of Notre-Dame exactly as they had been in the 19th century by covering them in lead deepened the anger already felt by the members of Notre-Dame Lead and raised the eyebrows of politicians, non-profits and local residents.
To justify the decision, the institution in charge of restoring the cathedral, Rebuilding Notre-Dame de Paris, ruled out any danger of direct exposure to the substance. “Covering the roof structures of the nave, the choir and two arms of the transept with lead does not expose any member of the public to lead, as they are located some forty metres from the ground and are inaccessible,” the institution told French daily newspaper La Croix in a December 2023 article, assuring it was taking the matter “very seriously”."
“But Notre-Dame was not the only location to be affected,” Toullier pointed out. “Lead levels were very high all around the cathedral, on metro platforms, in bookshops on the Place Saint-Michel and even in surrounding schools.”
At the end of summer 2019, Notre-Dame Lead reported levels of up to 123,000 μg/m², which represented 25 times the "standard" threshold of 5,000 µg/m² set by the regional health authority ARS, at the Place Saint-Michel, a 10-minute walk from the cathedral. “Yet no significant clean-up operation was carried out. It was as if the problem didn’t exist,” Toullier lamented.
“But what about run-off water from the roof, which will be laden with lead?” asked Thébaud-Mony. In a notice published in January 2021, the French High Council for Public Health estimated that “the roof of Notre-Dame alone … would emit around 21kg of lead per year (about two tonnes per century) in run-off water”.
“Lead could have been replaced by another substance like zinc or copper,” said Thébaud-Mony. “When alternatives exist, why choose lead and risk human health?” This was the case for the Chartres cathedral, destroyed by a fire in 1836. The original structure had lead roofing, which was replaced by copper when it was rebuilt. Though perceived as less stable, copper is significantly less toxic.If have thought the reduced weight quite a bonus too.
In more detail, Notre Dame's new fire protection system rests on five pillars.
The first is surveillance. “In addition to thermal cameras, an air suction and analysis system will be in constant operation,” explains the public institution in charge of restoring Notre Dame of Paris. “Any outbreak of fire detected by at least two pipes will automatically trigger the misting system.”
The system will release a mist consisting of fine droplets of water diffused into the wooden framework, which, if necessary, will considerably reduce the temperature in the space and smother the incipient fire.
The third pillar is the thickening of the batten: the thin planks of wood that separate the trusses from the lead roofing. “One millimeter thick has a fire resistance of one minute: We added 15mm [0.6”, editor’s note], giving the fire a quarter of an hour less chance of spreading to the roof,” explains the company.
Fire-stop trusses have been installed to separate the spire from the choir on one side and the nave on the other. They divide the space in three, preventing or delaying the spread of fire from one to the other.
Finally, the entire network of dry columns has been redesigned to facilitate firefighting operations. The flow of water that can be mobilized has been multiplied by three to reach up to 600m3 (264 gallons) of water per hour.Lead - the traditional material using for cathedral roofing is easy to work with, easily soldered to prevent leaks, but is heavy and is toxic when burned.
Copper - Also a traditional material that is easy to work with, also easily soldered to prevent leaks, is lightweight and non-toxic. But the roof would be green afterwards (once it oxidizes) not dull gray.
Steel - Lightweight, can be cut & bent to fit around crenelations. But can't be soldered - any waterproofing would have to be done with caulking & crimping other steel over joints. Available colors to match the original lead. Won't last as long as some other choices (it eventually rusts).
Composite asphalt shingles - just no.
Wooden shingles - Moderately difficult to work with. Easily burns. Will get moldy unless treated with chemicals.
Slate tile - Very difficult to work with, but inflammable. Heavier than lead and is brittle. But it would have a similar color to the lead its replacing.
Concrete tile - similar pros + cons as slate, but cheaper and doesn't last quite as long.
Color is ok. Anyway the original color of the outside of the cathedral was nothing comparable with the monochrome stone white of today (that's right, churches and cathedrals were artistically painted, in the Middle Ages).
And there are plenty of copper roofs everywhere in France, including on cathedrals.
Also you forgot to mention zinc.
Tradition is not always the right answer.
Or will you sweeten your wine with lead salts like in the 19th century, just because tradition?