AILSA CHANG, HOST:
We're going to turn now to someone who knows Notre Dame Cathedral inside and out. Art historian Caroline Bruzelius has spent years studying its Gothic architecture. Welcome.
CAROLINE BRUZELIUS: Hello.
CHANG: Now, I understand you actually spent years inside the cathedral. Can you tell us; what is it made of? Are you surprised that it caught on fire like this?
BRUZELIUS: Well, there are several things to talk about there. My work was on the cathedral while they were cleaning the interior. And I was taking advantage of that to go up a scaffolding up the height of the vaults, which are 108 feet above the ground, to try to study how the building is put together - to measure the stones, to record the moldings, to think about process of building what I call a mega-building. The cathedral was...
CHANG: Yeah.
BRUZELIUS: ...The biggest building of its time in Paris especially but in that whole region.
CHANG: And can you tell us what kind of stone it's made out of?
BRUZELIUS: So it's made out of Parisian limestone, which is quarried right there under and around the city. It's a beautiful quality of stone. But when it's exposed to fire, stone is damaged. It doesn't actually burn, but it loses its surface. It becomes friable. It chips, and it's no longer structurally sound.
CHANG: Yeah.
BRUZELIUS: But the fire, however, seems to have started in the roof. And what most people don't understand when they visit a cathedral is that above the vaults, there may be 50 to 60 or even more feet of timber that support the enormous roof above the cathedral vaults. So between the vaults and the roof, there is a forest of timber.
CHANG: Wow.
BRUZELIUS: I wish I could show you a photograph. This timber is old. It's very dry and porous.
CHANG: Very flammable.
BRUZELIUS: Very flammable.
CHANG: Now, a firefighter the scene said earlier that they're directing their efforts towards saving the artwork at the very back of the cathedral. Can you describe for us what kind of artwork is there?
BRUZELIUS: Well, a lot of that artwork was put in in the 18th century - great altar pieces, beautiful sculpture, pews - as part of an 18th century renovation of the cathedral. But there also are many, many works of art that date to the Middle Ages, not the least of which of course is some of the remaining stained glass and sculpture, all of which - because it was Notre Dame in Paris - was of the highest possible quality.
CHANG: Yeah. Now, Notre Dame is more than 850 years old. Has it ever suffered drastic damage on this level before?
BRUZELIUS: Nothing perhaps on this level.
CHANG: Yeah.
BRUZELIUS: Seeing that fire was heart-chilling, and it extended the entire length of the roof structure. The cathedral has been changed and damaged many, many times, especially after the French Revolution, which, as you know, was as much against the church as it was against the state. And a sculpture was torn off the facade. Many portals were damaged, and the stained glass windows had already partially been changed in the 18th century. So yeah, a lot of change has happened at this building, but this is a kind of cataclysmic change way beyond anything we've ever seen.
CHANG: Now, I understand you have dedicated many years to this cathedral. May I ask; what is it like personally for you to watch it burn like this?
BRUZELIUS: I would say heartrending. You know, we tend to take buildings for granted. People like myself who work on them and metaphorically crawl up and down the walls know, however, that even monumental architecture is very vulnerable and that maintenance and restoration is critical. Here, I don't really know what kind of anti-fire provisions they had up above the vaults, but clearly, as I said, this was - in some ways, that kind of wooden roof is an accident waiting to happen.
CHANG: Yeah. That's Caroline Bruzelius. She's a professor emeritus of art history at Duke University. Thank you very much for joining us.
BRUZELIUS: Thank you. Bye-bye. Transcript provided by NPR, Copyright NPR.