Name: Saving Notre Dame’s Iconic Stone Vaulting
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The water used to fight a fire at Paris’s iconic Notre Dame Cathedral and months of rainwater damaged the Cathedrals’ stonework but a team of geologist have a plan to save it.

Geologists attempt to restore limestone at Notre Dame Cathedral after a fire.

Saving Notre Dame’s Iconic Stone Vaulting

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The water used to fight a fire at Paris’s iconic Notre Dame Cathedral and months of rainwater damaged the Cathedrals’ stonework but a team of geologist have a plan to save it.

Geologists attempt to restore limestone at Notre Dame Cathedral after a fire.

Tech & Engineering

Saving Notre Dame’s Iconic Stone VaultingPublished December 22, 2022NARRATOR: On April 15, 2019, the 856-year-old cathedral of Notre Dame de Paris is undergoing a six-and-a-half-million-dollar renovation of the spire, when a fire breaks out inside the oak framework of the roof. After 90 minutes, the 400-ton timber and lead spire gives way and crashes through the stone vaulting. The fire destroys the roof and spire and leaves three gaping holes in the vaulting. With the loss of the roof and no protection from the elements for almost two years after the fire, the exposed stone vaulting was repeatedly soaked by rain. In the 18th and 19th centuries, restorers cast layers of plaster on top of the vaulting in case of a fire. This protected the stonework from the heat of the 2019 inferno, but not from the water used to fight it. This, along with months of rainwater, washed salt from the plaster into the lower layers of the porous limestone. As the moisture evaporates, the salt crystalizes and forces the limestone apart, destroying the inner surface of the vaulting. Geologist, Véronique Vergès-Belmin, will use a technique to draw the salt out from the stone. To extract the salt, Véronique’s crew will coat the vaulting with a paste of clay, sand and purified water, known as a poultice. The water from the poultice is drawn into the stone, where it dissolves the harmful salt crystals. As the clay of the poultice dries, it draws the salt water out of the stone, saving the vaulting from further damage.VÉRONIQUE VERGÈS-BELMIN: The poultices will be removed when they will all have dried.NARRATOR: They load the sticky mixture into a compressed air gun and spray it into every crevice. Finally, they carefully smooth the poultice across the areas affected by the salt damage.VÉRONIQUE VERGÈS-BELMIN: You can see that it follows very, very closely the surface of the stone. And what we recommend is that poultice should not be thicker than half a centimeter to one centimeter, otherwise there are risks that it falls down. We need to have a very slow process until the vaults are dry. But this will take time, much time.NARRATOR: The poultice may stay in place until the new roof is built and the vaulting is permanently protected from rain and snow.

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Saving Notre Dame’s Iconic Stone Vaulting

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