The Vaulting Held

[ Posted Wednesday, April 17th, 2019 – 16:34 UTC ]

The tragic fire at the Notre-Dame de Paris cathedral could have been a lot worse, especially at level of the ground floor. But to a large extent this further catastrophe was avoided. Images from within the cathedral show a surprising amount of the floor to be relatively unburnt, including standing pews made of wood. The thanks for this miracle, though, belong not to God but to some unnamed Medieval stonemasons -- those who did the design and construction of the building's vaulted ceilings. Because their vaulting held fast, widespread damage at ground-level was averted.

When you examine the architecture of a cathedral, one thing quickly becomes apparent: there's really not that much to actually burn. Almost the entire building is made of stone, metal, and glass -- none of which burn very easily. The only extensive use of wood is in the construction of what might be called the "attic" and the roof itself. This is where all the flames were coming from in the videos we all saw from France while Notre-Dame de Paris burned.

Anyone at all interested in the subject of cathedral architecture would be well advised to go down to their local library and see if they have a copy of Cathedral, by David Macaulay (1973). It is an illustrated children's book which details in pen-and-ink drawings how a cathedral is built, from the ground up. It is fascinating and well worth a read, as the architectural drawings are so good that even adults will enjoy learning how cathedrals are laid out and actually constructed. Or, if you're more inclined to read a thick, multigenerational saga, you could always check out The Pillars Of The Earth by Ken Follett, which begins with an intentionally-set fire in a cathedral attic and follows one family of stonemasons through the construction of an English cathedral in the Middle Ages.

I personally grew up in a house that contained the book Cathedral, and I've always been amazed at the level of engineering that goes into such monstrous stone testaments to faith. Notre-Dame de Paris was begun in the twelfth century -- a time when most people lived in wooden huts or, if a bit luckier, in a stone cottage. Poverty was crushing and lifelong for the majority of the population, and engineering and architecture were almost non-existent. And yet these were the people who built the great cathedrals, soaring hundreds of feet in the air and showcasing the finest artistry and engineering of the age. With only the crudest of tools, stonemasons could raise a wall so perfectly designed that it would last for eight or nine centuries afterwards. Problems with such grandiose designs happened, and solutions were devised to deal with them (such as the flying buttress design, to strengthen walls weakened by so many windows).

One of the biggest problems in such ambitious architecture is how to span the enclosed space created by the walls. Cathedrals are known for interiors that soar, seemingly up to heaven, with no pillars or crossbeams to break up the sightlines. What this means is that at an incredible height, somehow the walls must be spanned over, so a roof can be attached.

This is done with massive beams of wood. Crossbeams are laid and then a triangle of support beams is constructed above it. Line all these up and you've got the framework for the roof itself, which is laid with more wood supports and finished off with either slate or sheets of tin or lead. But while the top of the roof may be fireproof, all the supporting framework, being wooden, is not.

Of course, it would be ugly to gaze soaringly upwards from the floor of a cathedral and see the underbelly of the roof, so the interior is given a ceiling to look at instead. This ceiling is made of stone, in a pattern of three-dimensional archways known as vaulting. For one square portion of the ceiling, two criss-cross stone arches or ribs are constructed, and then a thin layer of stone is laid between the arches to finish off the ceiling visible from below. Each square portion of the cathedral gets a miniature dome, in essence, on top of it.

Because cathedrals are laid out in a Christian cross pattern, in the middle of the cross is the most vulnerable span of the ceiling, because it is usually the largest. So far, the photos from inside Notre-Dame de Paris seem to show that the central vault collapsed, leaving the center of the cathedral open to the sky. This would be the first place you'd expect the vaulting to fail, especially if this was also where the spire collapsed onto.

But from the limited video shots I've seen so far, it appears that the majority of the other vaulting actually held. The stonework did not collapse, and is now bearing the weight of all the burnt-up remains of the roof and roofing framework (and, for a while, the water used to douse the fire). It was never designed to hold this amount of weight, so there's obviously still a worry that further vaulting could collapse.

Getting back to cathedral design for a moment, though, even in the worst fires there is still not that much to actually burn in a cathedral. There is the entire wooden roof structure, and then there is nothing but stone and glass and metal in the rest of the structure itself. There is no wood in the walls, in the windows, in the buttresses, or anywhere else. There are side roofs at lower levels, with their own wooden framework, but they're smaller than the main roof. Then when you get down to the ground, there are artifacts made of wood here and there (pews, the altar perhaps, the pulpit, any Medieval carvings or booths or screens or other ornamentation scattered all around the cathedral, etc.). These could all go up in smoke if the vaulting failed and the embers of the roof fire fell to the ground. This would be the worst-case scenario, where everything wooden in the building burned. The stone walls could crack and even fail if the fire were hot enough. But they couldn't burn. The lead in the stained glass windows could melt and the glass fall out, but neither would actually burn.

Much of that was avoided in Paris, thankfully. The fire seems to have been largely contained within the roof area. Some of it fell to the ground, but it wasn't as bad as it could have been. The spire fell, but it was reportedly not constructed of stone (some spires are) but of metal and wooden bracing. This is why it collapsed so fast, because after the wood burned there was nothing to hold the metal up any more.

The French people and anyone else in the world who cares about Notre-Dame de Paris should be offering up thanks for the limited amount of damage to the cathedral. Those inclined to thank God for this fortunate event are free to do so, but the real thanks belong to some unnamed but incredibly skillful French Medieval stonemasons. Because they were the ones who did such an exemplary job of the cathedral's vaulted ceilings that they survived a catastrophe they were never designed for. The vaulting held, and by doing so saved a whole lot of damage to the rest of the cathedral.

-- Chris Weigant


Follow Chris on Twitter: @ChrisWeigant


24 Comments on “The Vaulting Held”

  1. [1] 
    Chris Weigant wrote:

    Taking a break from politics today....


  2. [2] 
    Elizabeth Miller wrote:

    Very nice.

  3. [3] 
    Elizabeth Miller wrote:

    Those inclined to thank God for this fortunate event are free to do so, but the real thanks belong to some unnamed but incredibly skillful French Medieval stonemasons.

    That is certainly true!

    But, what accounts for the great shape the copper rooster that sat atop the spire is in after falling of the spire and down to the floor of the cathedral. Amazing.

    And, then there were the two birds flying around the roof just above the flaming roof and the near pristine golden cross at the alter.

    But, again, thanks to the stonemasons … who, I might add, must have been rolling in their graves at the neglect of Our Lady of Paris through the years.

    I haven't been there yet but I hope to see her as she recovers.

  4. [4] 
    Elizabeth Miller wrote:

    Chris, would it have been possible to install a sprinkler system within the vaulted ceiling?

  5. [5] 
    Kick wrote:

    Nice article. I've seen her in person three times, and each time I visited there was a section under construction. I heard a fire alarm sounded and staff searched for 23 minutes unable to locate a fire and believing it might be a false alarm until a second alarm sounded and the fire was then detected in the attic.

    I sent a very nice chunk of change yesterday to help rebuild. Reconstruire dans 5 ans? *laughs*

  6. [6] 
    C. R. Stucki wrote:

    " . . .inclined to thank God for this fortunate event.", or perhaps inclined to wonder if it could be divine retribution for 20 centuries of unmitigated sexual abuse of untold numbers of the powerless and the helpless.

  7. [7] 
    TheStig wrote:

    I'm a big fan of the Macaulay book myself.

    Notre Dame was laser scanned to very high precision recently, that should be very helpful in reconstruction. You can see the 3D renderings on You Tube.

    The Cathedral is a 900 year continuing construction project, with a lot styles, many of which are anachronisms. The spire is...was constructed in the 19th century. Vandalism by Protestants and Revolutionaries destroyed Medieval statues and glass which were replaced by more modern styles. Industrial air pollution has been hard on the fine stone work.

    So, there is a bit of a Ship of Theseus identity problem facing they rebuild to 2019 standards, or do they strive for a more authentic medieval style. Or just continue the precedent of reinterpretation. Hand hewn, or power tools?

    As CW noted, hIgh temperatures can be hard on stone and metals. Especially when stones and metals with different expansion coefficients are in contact with each other. That fire looked really hot!

    I understand a billion dollars has already been commiitted to the reconstruction. I think that will be a few bricks short, but it's a great start.

  8. [8] 
    John M from Ct. wrote:

    Very nice break from politics to something more ... eternal.

    The NY Times today reminded us of something you alluded to: the vaulted stone ceiling only collapsed in the center, but all of it has been exposed to high heat and soaked with water. The French engineers are taking the approach that the cathedral's structure may have been compromised in ways that are not immediately apparent. A quick dash to bring in the masons and carpenters to repair the vaulting and replace the roof and spire may have to wait while the fundamental strength of the ceilings and walls is tested and proved.

    C.R. [6]: I know what you mean, but why now? Why not expect God to blow up the cathedral during construction, when very likely the powerless and helpless were suffering the rule of the Church even more than now? Why not in the 15th or 17th centuries (ditto) or the 19th century (ditto)? Why would not God have blown up every single cathedral across Europe, and slaughtered all the sinful clergy up to and including every Pope since Peter himself, if 'divine retribution' is, as you wonder, the reason for this disaster?

    I suggest it's completely unrelated, and disrespectful of humanity's almost unanimous reaction to the near-destruction of a masterpiece of devotional art, to link this event to a (as you assert) 2000 year old contradiction within (at least) the Catholic Church.

  9. [9] 
    C. R. Stucki wrote:

    John M

    As an agnostic, I'm not the one to answer any of th 'whys' and the 'why nots'. I'm actually not even able to advocate for the "divine retribution" theory. I basically tossed that idea out for those of the opposite persuasion to give them something to ponder, and to stimulate discussion.

  10. [10] 
    nypoet22 wrote:

    i've only been once to 'Île de la Cité' and gave up on waiting in an enormous line to see the top floor. still the cathedral was spectacular. as a jew i may not get the same reaction as christians might, but it's still damn impressive.

    i suppose any practitioner of science must remain agnostic as a matter of proper investigation. but there's a point where it's insufficient to perpetually reserve judgment, where it diminishes one's ability to fully experience the world.

    “It's not atheists who get stuck in my craw, but agnostics. Doubt is useful for awhile. We all must pass through the garden of Gethsemane. ... To choose doubt as a philosophy of life is akin to choosing immobility as means of transportation.”
    ~yann martel, life of pi

  11. [11] 
    Kick wrote:


    Just when I thought you had made it through an entire post without mentioning it:

    ~yann martel, life of pi <--------- Whoop... there it is! ;)

  12. [12] 
    nypoet22 wrote:


  13. [13] 
    Kick wrote:

    If my sources are correct, a man carrying 4 gallons of gas, 2 bottles of lighter fluid and lighters was detained by a security guard who flagged counterintelligence officers who caught up with the man on 50th Street. The suspect informed the officers that his car was out of gas; it wasn't.

    Location: St. Patrick's Cathedral, Manhattan, New York, New York

  14. [14] 
    Chris Weigant wrote:

    nypoet22 [11] - a jew i may not get the same reaction as christians might, but it's still damn impressive.

    I had this reaction, as an engineer: "This is one damn fine example of engineering in the darkest of ages of man!"

    I paid the extra to walk up hundreds of stairs and see the bell tower and the gargoyles up close and personal. It was pretty amazing, I have to admit!



  15. [15] 
    Michale wrote:

    Laguna Beach Keeping Patriotic Patrol Cars After Debate

    LAGUNA BEACH (CBSLA) — The Laguna Beach City Council voted on Tuesday night 4-1 to keep the American flag design on the city’s police vehicles.

    Dozens of Laguna Beach residents had lined up to urge city leaders not to remove the American flag logo from the police cars.

    “To take that graphic off of that car would break my heart,” a resident told the council.

    The Laguna Beach City Council initially approved the American flag lettering for its police department. But after some accused the department of being too aggressive and militaristic, Tuesday night the council voted again.

    Apparently, there IS sanity left in this country... In CALIFORNIA of all places..

    I pity and feel REALLY sorry for those Americans who think that the US Flag does not "represent the standards of the community"....

    Maybe they would feel better in Russia.. Or China... Or Iran...

  16. [16] 
    Michale wrote:

    Oh Crap!!!!

    CW.. Can you delete #16 and put it in the OUTFOXED commentary...

    My bust...

  17. [17] 
    ListenWhenYouHear wrote:


    " . . .inclined to thank God for this fortunate event.", or perhaps inclined to wonder if it could be divine retribution for 20 centuries of unmitigated sexual abuse of untold numbers of the powerless and the helpless.

    As a Christian, I have always scoffed at the idea that God would use disaster to punish man for sins they committed in the past. That is because that type of punishment has too much collateral damage to be just. If someone committing a sexual assault trips and falls ten stories to their death, I might be more inclined to think there was divine judgement involved.

    More importantly, the death of Jesus Christ ended man’s need to offer blood sacrifices to repent for our sins. In the OldTestament, man’s need to offer sacrifices to atone for our sins was constant. In the most simplistic of terms: with Jesus’s sacrifice on the cross, payment became due at the end of our lives.

  18. [18] 
    Chris Weigant wrote:

    I just have to add one more plug for the book "Cathedral". If you love good drawing, if you've ever wondered how cathedrals are built, if you love knowledge for knowledge's sake, check out this book.

    These people had only the crudest of implements, unchanged in centuries, and they built something which has more than stood the test of time. How many architects or builders today build for the centuries? Not many, outside of giant concrete structures like dams and the like.

    Anyway, check this book out, it'll only take you like a half-hour to read and it is absolutely fascinating!



  19. [19] 
    Elizabeth Miller wrote:

    I'll read it!

  20. [20] 
    ListenWhenYouHear wrote:

    Kick [14]

    I also heard about that... supposedly the guy is a philosophy professor....not sure if he was trying to create an incident for class or if he was just knockers and looking to feel the burn.

  21. [21] 
    Kick wrote:


    A philosophy professor!?… walks into a cathedral with all the implements to commit arson multiple times over!? It certainly seems like all that philosophical wisdom of his went right out the widow. Nuts! :)

  22. [22] 
    Kick wrote:

    out the window, of course.

  23. [23] 
    nypoet22 wrote:

    well, out the widow and it would be an entirely different type of story...

  24. [24] 
    Kick wrote:


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