span across entire banquet halls (6-12 meters) without noticeable sagging while also carrying joists between them and being expected to carry the load of people walking above?

I tried asking in 50 different "ask whatever" subreddits but that site is a hellhole where you aren't even allowed to post unless you're personally vetted by Langley, but I don't think you autists would ever let me down, so here goes nothing (if this gets removed here too for being off topic, I might as well just give up from using the internet). Here's a copypasta of what I tried posting there (can't post at first due to char limit):

>>2929680 (OP)
Here it is

So if you Google "French chateau painted ceilings", you'll see loads of pretty similar looking ones whereupon what looks to be a 30-35cm (12-14 inch) deep beam is carrying loads of small joists across very VERY vast rooms. Now from what I know, theoretically you can safely span a beam 1.5x in feet of it's depth in inches but in practice it's hard to span a beam more than it's depth if it's also expected to carry the weight of joists, ie 12 feet for a 12 inch deep beam carrying the weight of floor joists, but they are spanning what looks to be 12 inch deep beams 2-2.5x the distance in feet without any real sagging despite the fact they're supposed to sag just from being forced to support their own weight at that point if you force them to go that far.

The only solution I could think of was that they are cantilevering the beams a bit on both sides of the room at the ends while also putting a very heavy weight on top of the cantilevers to keep the beam from bending. That's an answer rooted in basic physics at least, but if that's the case, why isn't it talked about more? I can't find anything about this on the internet so I thought I'd ask here.

OP Picrel is an amazing example of what I'm asking - there's no way modern civil engineers would sign off on those big beams spanning even half the distance they are on the pic, it's overkill to a comical degree. You'd absolutely expect them to sag just from their own weight at that point, but no. So what gives? How the baguette gang do it?

>>2929680 (OP)
bumping before bed ig

>>2929680 (OP)
real answer: it probably CAN'T hold the load of everything above it. it wasn't designed with any engineering behind it. Some builder back then just said "it worked last time i did it" and threw it together. if you added another ton of weight on it, it would probably all come crashing down.

>>2929680 (OP)
Wide span ceilings or very wide span ceilings examined closely would probably reveal that the distance between the bottom of the ceiling and the exposed surface of the floor surface above it, is considerable. Considerably greater than one would commonly encounter in a standard modest domestic dwelling. That hidden space which is invisible, contains cross-bracing elements. Typically those are subject to tension hence very resistant to loading.

The ceiling is constructed from compound girders or in this case beams. The visual clutter is hidden. The floor/ ceiling combination is mechanically what we would identity as a bridge.

>>2929730
Probably this, and also most building materials are way stronger than engineers give them credit for. They have to leave a margin of safety for the absolute worst examples of a beam that size and calculate based on those safety margins.

>>2929681
>You'd absolutely expect them to sag just from their own weight at that point, but no.
I wouldn't, maybe you're just too used to stick buildings
All the old carpentry is wildly oversized, it's not going to move a bit, especially for this fancy stuff where they could pay to bring the best timber from afar

>>2929681
> Now from what I know, theoretically you can safely span a beam 1.5x in feet of it's depth in inches but in practice it's hard to span a beam more than it's depth if it's also expected to carry the weight of joists
The joists themselves rest on the walls, their full weight is not on the beams. The beams and joists are very strong old growth oak from Normandy and after the 16th century imported tropical/african hardwoods from the French colonies, including Azobe (they basically clear cut the colonies for timber and farming) and they hid structural elements everywhere.

>>2929680 (OP)
What you’re seeing is not beams, it’s a box of light panel material built around one, built after installing the beams and self carrying. The beams can sag further inside these ‘boxes’ (to some extent), and it would only be visible on the floor above, where it can be compensated by shimming the floor.

>>2929681
I wonder if they preloaded them
Also don't let modern safety margins and shit tier farmed lumber confuse you.
They had much better lumber, it would act closer to modern laminated beams

>>2929752
So, what you're saying is it's possible to nail something like 2-3 Pratt or Howe trusses together or just have one done out of thicker timbers, and then put a cosmetic box around it to span 25 feet or so for a larger room? I could consider that.

Then again >>2929772 >>2929787 >>2930165
are probably right, you could just get a big beam anyway and shim it on the upper end. The breaking strength on something like an 8x12 is just mind boggling especially if it's quality hardwood or something close to it like Southern Pine, I doubt it'd fail. It would cost marginally more than four 2x12s nailed together but I think it'd still be worth it unless you're planning to have like 30 of them milled.

>>2929681
>1.5x in feet of it's depth in inches

Fuck you for making me read this.

>>2930376
I agree with this angry doge

>>2930376
It's true though, old tradie rule of thumb. Not saying code will necessarily agree with it everywhere, you'd be off by like 10-15% especially with smaller joists, maybe you'll need to space them two inches closer but that's about it.

Other posters are right. The actual structure (which no doubt does have some deflection) is hidden behind decorative finish work.

>>2929730
Builders learn from instructions by architects and hone the knowledge from experience and pass it down. people are smarter then you give them credit for.

Theres two answers
First is the sad truth that they often did sag, and it was a pain in the fucking ass to replace, but the wood was strong enough to last a long ass time before it needed to.
Second, the more interesting answer, is that on walls that are jettied (overhang, like in pic rel) the floor is actually more likely to bow than sag. This is because the beams are propped up over the wall beneath them, but the wall above them sits at the end of the beam, so the edges are pushed downward with the full weight of the floors and roof above and the middle of the floor is strengthened.
A stone building would either be narrower than the wood ones or their would be a wall(s) down the middle acting as a support.

>>2931355
wait im retarded thats not jettying, this is jettying

>>2931355
Yeah, I suppose that's the most viable answer, even mentioned in the OP (cantilevering on both sides). I think the vast beam spans even help in this regard because the potential bowing counteracts the potential sagging, if that makes any sense. At least that's how I picture it. On historical jettied houses even comparatively miniature 4x4 joists tend to run on a long ass span usually.

Why don't you just do a beam deflection calculation with the stiffness of what this guy said (>>2930165) and some eyeballed dimensions?
This is a question you can answer for yourself without all the vague guessing in this thread.

I visited a museum farm this weekend and there was this nice xbox hueg beam
10m long, something like 60/70cm section, 4 tons of oak from 1580
[spoiler]I didn't get a good pic of it so you get whatever I found online[/spoiler]

>>2931473
From outside

>>2929787
This and also, when the box enclosure starts to crack or move or look a little bit crap some artisans come in, remove problem individual panels that make it up, refit or rebuild them, retouch and reinstall. You might find some or all of the underlying beams are steel by now too.

>>2931484
Wtf is this bullshit? You think nobles and people rich enough to afford this would cheap out and be the laughing stock of the country?
>some or all of the underlying beams are steel
10/10 bait enjoy your (You)

>>2931484
>>2931500
>steel beams
All we need is jetfuel now and we're golden, topkek. Why steel when you can span 30 feet with a wood truss anyway without it even sagging. Either that or add some weight at the ends like the OP himself said as well as several other people here. The premise of the thread is kinda dumb when you think about it but I'm glad it's here for posterity's sake.

>>2931500
>>2931549
Its obviously some municipal - floor hazard cone, ugly sign in English. Look at that municipal floor ick. There's a fair chance its a complete rebuild as part of postwar lipstick, done by German or some other city that got flattened. Its got that clean and colorful vibe. In which case 100% the hidden beams are steel.

>>2931583
Pic related

>>2931583
>municipal - floor hazard cone, ugly sign in English
Uh what
OP asked specifically about french castles carpentry and posted a pic of a famous royal castle
Say nigger now

>>2931584
topkek, I actually laughed out loud... the filename literally says
>chateau de blois
actual retard, here, have your (You)

>>2931983
>>2931605
Thank you for your insightful contribution, I was moved to consult Wikipedia. So yes - steel beams very likely. Although it wasn't bombed.

>>2930423
I think they were getting on the phrasing. "The distance it can span is generally 1.5 feet for every inch of depth" would have been clearer.

>>2932005
>steel beams in 1840
If this is bait, good job. I don't know why you're categorically denying the possibility of a wooden beam setup that can span that distance, especially given the fact there's a few already named rather unsophisticated solutions people have used to span it in the past.

>>2932062
If they repaired the room later than 1918 its likely steel, so repair in bit over the last 100 years. Otherwise probably wood. This is France- if it was the UK I would say from 1900, and possibly even wrought iron before that. British technology/cheapskates.

>>2931473
Holy shit thats beam and a half right there.

>>2931355
Needs to be torn down and lovingly rebuilt using as much of the original material as possible.

Am I the only one who took a minute to appreciate the beauty of this place?

>>2932073
All these castles or rich merchant houses with painted carpentry are 99% classified historical monuments, you can't do whatever the fuck you want and certainly not put random steel beams when renovating

>>2931356
Is it legit to cut through that brace like that for the window?

>>2932200
Looks good from my house.

>>2932119
1918 etc is not "now".

>>2932963
They started protecting them in 1840 iirc

>>2929680 (OP)
The beams had several advantages over modern timber.
First, the beams were generally old growth timber (which may or may not make the lumber stronger, depending on type of wood), but which usually has tighter, straighter grain, resulting in stronger timber.
The beams would have been felled by lumberjacks who knew what they were doing, and who would possibly have felled the timber during winter, which can result in stronger timber.
The beams which needed to be cut down in width, would have been more likely to have been riven, for thickness, and dimension, at least before surface work, resulting in maximum strength, due to straight grain running the length of the beam.
The lumber might have been floated down a river, with the water logging effect removing sap from the timber, resulting in a stronger lumber, (winter felling also results in less sap in the wood).
The beams would then likely have been air dried, which can also result in a stronger, more resilient lumber.
The beams in older buildings are usually way thicker than in modern buildings, sometimes four times as thick, and if you look at that ceiling, more beams were used, resulting in a ceiling that is 40-50% beam.
There are also even larger cross beams, supporting the longer beams perpendicularly.
Then, whether nails or wood pegs were used, the lumber once in place would have continued air drying, locking any nails or pegs very solidly in place.
That ceiling/floor, acts practically as one giant piece of lumber, like modern cross laminated timber.
The lumber used might have also been a hardwood like oak, which has a high stiffness, especially compared to softwoods.
Floorboards nailed to those beams from above would also act to lock the lumber stiffly together.
Basically, every traditional technique for ensuring timber strength, from decent lumber, to fastening type, would have helped ensure the floor’s stiffness.

>>2929680 (OP)
they appear to be visibly sagging in the photo you posted...

>>2929680 (OP)
Wood is stronger than it looks. The redwood ceiling beams at Mission San Francisco de Asís are still holding strong over 200 years later complete with the native Ohlone paint job.