Notre Dame

[DerbyBorn]

The cathedral has flying buttresses, presumably to take the outward forces from the roof tending to push out the walls.

With the roof gone - why aren't the buttresses pushing the walls inwards?

[Harry Bloomfield]

DerbyBorn wrote on 16/04/2019 :

They were not only supporting the roof, but also the stone of the vaulted roof under the main roof. It basically had a double roof and most of the stone vaulting has survived.

[Custos Custodum]

Newton3

[Chris Green]

From an engineering point of view I seem to remember that flying buttresses are pretty much pointless, they are decorations rather than something holding up the wall.

The building was almost certainly built up to roof level (including any/all buttresses) before the roof was put on anyway.

[Tim Watts]

That doesn't seem right.

They clearly add lateral stiffness to the wall and if they have full foundations, they are increasing the effective area of the foundations so resisting turning moments on the wall much like tree roots.

[Brian Gaff]

I don't think they work that way. There are lots of ruins with flying buttresses still intact. After all when you build the structure the roof is not on to start with, they would hardly make it so it pushed the walls over while it was being built. They realised that the strength in compression was what was needed to stop the uneven shearing force of the roof cracking the walls that is all. Brian

[Scott]

Why is the cost being met by donations and the French State and not by insurers? A Google search suggested it is French Government policy (excuse the pun) for the state to meet the cost of damage to national treasures. Same here of course for goverment assets, which are self-insured (try insuring an aircraft carrier for use in a war zone).

However, I assumed the building was owned by the RC Church. Would it have been donated to the government at some stage? Sale and lease back?

Glasgow School of Art apparently does have full reinstatement cover. I wonder if there is any 'small print'?

[jkn]

Interesting interview on R4 re this yesterday; apparently, despite the secularisation of the French State, the government owns most churches and similar buildings (the larger ones). I didn't fully grasp the arrangements under which they Church occupies them.

J^n

[Tim Streater]

Giggle for 'ownership of churches in france'

[Scott]

Does a full repairing lease not usually require the tenant to incept insurance?

[The Natural Philosopher]

Flying buttresses are not pointless at all.

They act as ypu describe.

[newshound]

+1. During the fire, the collapse of the stone vaulting was one of the big concerns.

Bear in mind there is probably a reasonably high factor of safety in those gothic cathedrals which have survived 800 plus years. (Many towers have collapsed, of course).

[Peter Johnson]

Don't know, but in Paris they have been arguing for years about who should pay for the repairs needed at Notre Dame.

[harry]

Every part of the flying buttress is needed. Including the mini spires you see on some,

[Harry Bloomfield]

Chris Green pretended :

Not the way I understand it. The flying buttresses were a solution to the problem of unsupported walls failing.

[NY]

In the specific case of Notre Dame, or in general?

I would imagine that early churches had problems with walls bulging outwards under the weight of a heavy lead-covered roof. And those buttresses would be built afterwards as a remedy. But any churches built after the problem was known about would probably have buttresses designed in from the start, to correct a problem that would only become apparent once the roof was eventually added.

Do buttresses exert much inward force on a wall that does not yet have a roof to exert an outward force. Or do buttresses general exist mainly to resist the outward force without exerting much of an unbalanced inwards force in the absence of a roof?

[soup]

The roof hasn't gone it is still there. What has gone is the wooden structure (Clad in copper?) that was covering the roof.

[Harry Bloomfield]

NY wrote on 17/04/2019 :

If you look at the design of a buttress, they form one half of a bridge shape. A stone bridge only remains standing, because there are two halves to it - one half props up the other half, remove the keystone and both halves collapse. So a buttress leans against the wall for support.

[tony sayer]

Clad in Lead that was the most likely cause of the blaze metalworking was taking place up there!..

[Tim Streater]

No, the roof has gone. What is left is the ceiling, which in this instance is stone. Some bits of that have gone too, such as where the spire fell in, but it's mostly still there. Just as well, too, as otherwise the walls might have gone.

The roof was clad in lead, about 200 tons, which all melted. Dunno where that is, although some may well have burnt.

I'm puzzled as to why so many questions are being asked here that could be answered simply by reference to Winky and other sites, and even the Beeb.