Pulaski

If the restored cathedral is comprised entirely of stone, concrete/ mortar, steel, lead, and glass, with only nominal amounts of wooden furniture and fabric carpets, and curtains (and none of these combustible items are in the roof space), what is going to catch fire? ….. Therefore I would argue that the strength of steel in a fire is entirely moot in this context.

scrubbedexpat142

So you've contradicted yourself again - wittering on about the "non combustibility" of steel!

Pulaski

But they already used "improved technology" to replace the stone spire on the roof of Notre Dame, when it became known that it was dangerous. I think the same argument applies to using a fireproof material in a concealed location - because functionality is paramount.

FWIW churches and cathedrals have been replacing bell frames for decades that were timber, and had been for centuries, with steel bell frames. Nobody has ever, to my knowledge, argued that that a steel bell frame isn't authentic and has no place in a Norman cathedral or church, concealed high up in the tower, where it is has little visibility, but function (strength and resistance to wood-eating insects) is paramount.

Pulaski

Are you saying that steel can catch fire?

scrubbedexpat142

Further discussion has become pointless.

Pulaski

It is if you can't be bothered to explain what you mean.

None of stone, concrete/ mortar, steel, lead, and glass can burn on their own (without fuel, such as timber or oil) under anything but rare and peculiar circumstances, such as concrete in an "oxygen fire". So if your building comprises only these materials, what is going to burn?

And if the answer is "nothing", when will steel ever reach 560ºC?

And if the answer to that question is "never", then why is steel losing 50% of its strength at 560ºC relevant?

zzrmark

I'm old school when it comes to materials, Oak worked perfectly well over the centuries and would be my first choice. As a time served shipwright I can say with some authority that I wouldn't touch French Oak with a barge pole, it is good for railway sleepers and that's about it, perhaps it's just the way it grows nowadays but I doubt it, German Oak isn't much better.
I have used Glulam beams a few times here and in the UK, structural engineers like it but just how well does it last over time? I am always wary of modern laminated products because the bottom line always wins out and I'd like to know just what they use as a glue. Epoxy is a modern favourite but it is crap when used with wood in hot and/or wet environments, Cascophen for the win but I know it isn't used in Glulam - awaits response from the pro-epoxy brigade who have never seen epoxy turn to a gooey useless mess when it suffers from repeated heating and cooling and had to sort it out...

Steel is a great medium but does it have the same kind of low maintenance lifespan that oak does?

I think the first question that should be asked is what kind of exterior aesthetics do you want from the roof, closely followed by do you want it to be low maintenance with high initial outset or settle for lower initial build coats but resign yourself to higher maintenance costs?

Pulaski

I don't know about oak roof trusses, but timber bell frames certainly last centuries, but not for ever. They are susceptible to wood-boring beetles aka "woodworm", but don't need painting, or at least they aren't painted.

However steel frames do go rusty, even if they were painted originally, and scrambling around in the confines of a bell tower with a wire brush, scrubbing off rust, then painting with red oxide primer isn't much fun. In any case many of the surfaces are inaccessible - imagine a climbing frame assembled inside a room where the framend almost touches all four walls and you'll get the picture.

It'll be about 300 years before we'll know if steel frames can last as long as timber frames.

Boomhauer

If strength and weight are an issue, and judging by the amount of money pouring in and the French government's promise to restore it fully, why not just go with Carbon Fiber beams.

Resistance to combustion should be more than suitable.

" Flammability: Though Carbon Fiber is constituted of carbon which is flammable, the fiber itself dose not flare up even if ignited by flame of match or gas burners. If heated up higher than 400 degree C together with some fuel, the fiber slowly burns (oxidized) but stops burning right after the burning fuel is removed. In this aspect, Carbon Fiber is categorized as "incombustible" under the Building Code of Japan. "

https://www.carbonfiber.gr.jp/englis...al/safety.html

Pulaski

A couple of hundred feet off the ground, and supporting a steep-pitch roof, carbon fibre might not be heavy enough. In traditional stone and timber beam buildings, the weight of the materials and friction are responsible for at least some of the resistance to wind loads. Of course if they go with traditional lead roofing again, it should deal with that concern.

zzrmark

Wood borers are not a problem in oak heartwood, unless it is already rotten, it's the sapwood they love.

Pulaski

Honestly, I am not certain if the insect damage I saw was in oak or another hardwood. In any case for timber that had been sawn at least 200 years ago, the damage was very modest.

dc koop

Hundreds of millions of Euros suddenly appear out of the woodwork to re-build a shrine dedicated to the virgin mother of a man who spent a lot of his life working among the poor. Paris has one of the worst homeless problems in Europe. Irony hardly describes it.

Lion in Winter

The Christian church has always had money or had access to money that it does not redistribute, and its priests and other staff have always lived well and loaded with riches. As an institution it is corrupt and always has been. It could always have put more money into the preservation work so direly necessary for Notre Dame as well, well before the fire. The restoration needs had reached crisis proportions. However, in terms of the preservation of history I am still glad that work will now be done.

scrubbedexpat099

Not sure what your post has to do with this as Notre Dame is owned by the French people and has been since 1905.

So it is the responsibility of Macron not the Church.