Hello, I'm renovating a bathroom in an old kitchen located on the upper floor of my house, which was built in 1945. The joists have a span of 4 meters and have dimensions of about 70x220 when I checked. There's a wall on one side 1.5 meters in, so the room is only 2.5 meters. I've glued 22mm particle board to the joists, then glued floor gypsum on top of the particle board, and then leveled with 35mm of self-leveling compound. That's quite a bit of weight. Does anyone have any idea how much load joists of this dimension can bear? One can't really know what load-bearing class it is. I assume they over-engineered a bit in the past.
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· Västernorrland
· 12 034 posts
I don't know if it was taken into consideration, but people rarely cared about it swaying. Today, it's an extremely important parameter if you're going to build a bathroom and use self-leveling compound. Now, I don't know how many beams you have, but spontaneously it sounds like you should have added something extra before laying down boards.
I would probably have (instead of floor gypsum) reinforced the joist layer by adding an extra beam to achieve cc300. It might not need to be 70x220 but somewhat smaller in height and inserted at appropriate places. Then I would have floated directly on well-primed chipboard with reinforcement mesh.
Now you have already made considerable progress and with the dimensions you mention: 22 chipboard + floor gypsum + 35 mm fiber, it will probably be very stiff anyway.
When it comes to 40s houses, they are often over-dimensioned in general, but not without flex for that.
Now you have already made considerable progress and with the dimensions you mention: 22 chipboard + floor gypsum + 35 mm fiber, it will probably be very stiff anyway.
When it comes to 40s houses, they are often over-dimensioned in general, but not without flex for that.
With a 4m span and 220 high beams, I believe that aligns with today's dimensioning tables, although now it's probably 225mm that's applicable. Gluing floor gypsum (with the right type of glue!) should provide a stiffening equivalent to having cc30 instead of cc60 between the beams.
Nothing wrong with floor gypsum as such, but older houses can be quite uneven, making it difficult to get gypsum boards (or other boards for that matter) to lay flush across the entire surface. And gaps that glue and screws do not bridge are not desirable in this situation.
Then the durability can be better if you pour thicker, but on a simpler, yet well-regulated base.
Then the durability can be better if you pour thicker, but on a simpler, yet well-regulated base.
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Yes, I'll sit down one day and calculate it. I'm not directly worried but it might be good to have a figure for safety's sake. I've had a bunch of self-leveling compound bags stacked where the bathtub is supposed to go, which was probably 400kg, so it should bear the weight. It would be interesting to measure how much the floor flexes under load, especially with regard to the tiles that are going to be laid.
As for the insurance company, to my knowledge, Folksam, which I have, should approve it. We had it in our previous house.
As for the insurance company, to my knowledge, Folksam, which I have, should approve it. We had it in our previous house.