I'm working on a small project to renovate a part of the basement that hasn't been finished before, nothing unusual really except that there is rock, lots of rock there now.
I've actually come as far as I initially intended, but I'm probably considering continuing so that more or less the entire area is cleared. To make it a bit easier, I'm considering tearing down the load-bearing wall that stands directly on the rock because it will be much faster when you don't have to fiddle around trying to chisel as close and straight as you can under it. Moreover, the rock level rises further out towards the outer wall, and I will need to go down about 1m at the end.
It should also be easier and better to make the new floor with insulation and casting in one go without a rock ridge sticking up in the middle.
I'm thinking about tearing down the blue-marked section and replacing it with pillars I anchor directly into the rock and then hide in the new wall. The plan is also to cut out the green section for a new doorway. When it's finished, the idea is to have interior walls according to the orange marking, but they shouldn't be load-bearing.
The question is whether it's possible to install 3-4 steel pillars with a top plate or if you need pillars + crown beam? The concrete slab is from '57, 15cm thick with unknown reinforcement.
What ceiling height do you have to work with, considering the beam against the upper floor structure? It's a long span, so it's not wrong to have one like that.
A steel beam across the entire span, 7.1 meters, must be at least HEA 280. This is under the condition that there are no load-bearing walls on the floor above, which there likely are. A section and floor plans of the higher floors are needed to fully understand the conditions.
The roof trusses are self-supporting, so it's "only" the weight of the interior walls and furniture that loads the floor structure in addition to its own weight.
I'm thinking of placing VKR80x80x5 at about 1.5m spacing, which I will weld onto plates and bolt fast at the top and bottom, then hide them in the new interior wall. The buckling length will be 2.5m, and they can withstand about 20 tons each if I read the tables correctly.
Placing a crown beam and getting it to fit well against the ceiling will just be tricky, it's so roughly and unevenly cast that it gaps by several centimeters wherever you place the straightedge.
One can probably assume that the reinforcement of the slab is done considering that the wall exists. Skipping the crown beam is a gamble that I would not take. But with columns on c/c 1.5 m, an HEA 100 is sufficient. There are ways to mount it without the underside of the vault causing too much trouble.
That I didn't think of that, I could have just checked with a magnet, it's 10x10cm and there's 10mm iron where I see the reinforcement where pipes and other things have been drawn through.
Now the wall has been torn down and replaced with 4 80x80 columns since sometime in February and my reference points haven’t moved at all, so it seems to be working.
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