I have a shaky/unstable floor in the living room (360x575 cm) and I know why, but I'm a bit unsure about how to best fix it. The problem is that it's a cast beam slab from 1929 that is probably poorly reinforced. Under the living room is the garage in the basement, and there they've tried to fix it with a box beam/square laid on the "flat" side, so it's quite bent. If you jump or dance in the living room, the whole floor shakes. What dimensions do you think would be required and how many beams to fix it? I should add that the ceiling height in the garage is no more than about 190 cm, so low construction height is preferable.
Not an entirely uncommon problem, unfortunately. Is the concrete the floor in the room above or is there a wooden floor on top? If the answer is yes, how tall is this structure? The concrete was probably part of the fire protection. However, the height in the basement is unusually low for being from 1929.
There is a parquet floor in the living room, and I suspect it has the same construction as in the old kitchen, where there are about 10 cm high joists on the concrete and then filled with slag before the wooden subfloor was nailed in place. So there is unfortunately no room to put up joists above the concrete, and I don't dare to tear everything down, you never know what might happen to the basement walls then. The only solution is probably to prop up and install a few more beams on cast pillars. A lot of work though.
How many and at what distance do you think it will take?
There is a possibility for better ceiling height since the garage floor is about 15 cm higher than the driveway outside, but it is a lot of work since there is rock underneath, so there is a risk that a lot might need to be split.
I meant that you place the steel beams above the garage roof as a replacement for the existing wooden joists so that you get a stable floor that does not affect the concrete.
