Bathtub installation in an old house with wooden floorboards

Hello everyone,

I want to install a bathroom in a house built in 1927. On the ground floor. There is a wooden floorboard that apparently lies on wooden beams and 17 cm of filling up to the floor. Wooden floorboards 3 cm. However, I cannot say anything about the floor/kitchen ceiling underneath.

Could I, in order to level the height with the rest of the rooms a bit, use Ytong blocks instead of the filling and then put tiles on top? There should be a walk-in shower and bathtub. For the drainage of the shower and bathtub, I could make appropriate recesses in the Ytong.

I would be very grateful for the fastest possible answers, we want to move in next weekend.

If needed, I could send pictures of the floor construction by email.

Greetings

Hello "Viper".
I'll put it this way:
Installing wet areas in a house built with timber construction is already one of the most challenging things in terms of waterproofing that you can encounter.
Now, if I may say so, looking at your questioning remarks, you want to work with Ytong blocks instead of backfill between the timber frames—surely you are not an expert in this field.
Based on this, you also want to move in next weekend without any further planning.
No offense intended: there is a reason why no one has responded to your request so far. The whole thing is unplanned and will lead to disaster shortly after any kind of implementation phase!
The floor structure must be properly planned; this includes uniform leveling, a self-contained shower tray, and suitable waterproofing measures on the walls and floor.
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Regards with the hope of being heard: KlaRa

My intention was simply to find out whether it would be sensible to replace the screed to remove the floorboards. I have already installed a small bathroom in the house with a standard shower so that I can move in. We simply do not have the means to afford paying both rent and mortgage for several more months. For the past two months, I have been working every evening after work until late at night renovating the house. This is the first time I have come across a problem. I knew that the ceiling between the first and second floors is a wooden beam ceiling with screed, etc., and I thought that the ceiling from the basement to the ground floor was a normal concrete ceiling with beams and floorboards laid on top. Maybe it is even that way. And I did not want to install a wet room in the wood but rather to completely remove the wooden floorboards and the screed. This was what my question referred to.

And therefore, it would be nice to get a few tips instead of just statements like that. I have now also decided to remove the floorboards only in the shower area and otherwise to rebuild on top of the floorboards with leveling compound, decoupling mat, screed, and tiles. Like in the small bathroom.

I am aware that I need to seal especially well. I already have the appropriate paint/sealant since I worked with drywall in the upper bathroom.

So what would now be the most cost-effective solution for our shower? Can you make a statement about that? As I said, remove the floorboards in that area and then build up with construction boards, OSB, or something else? Or would it also work with Ytong as a base structure? Then build on that accordingly with screed, etc.?

By the way, the house is solid and only has beams resting on wooden joists, which in turn rest on concrete or brick. Hence the picture where I shoveled away the screed and drilled a hole to see what was underneath.

Regards

Hello "Viper".
The initial information did not suggest what information followed later.
Regarding old screeds, the best solution will always be to replace them.
Depending on the age of the building, one encounters unpleasant backfill materials.
With different height levels per residential floor, the use of a bound backfill can prove to be more sensible before starting with aerated concrete blocks.
The backfill can be distributed more evenly and adjusted to the height, whereas with Ytong blocks and similar, the top edge must be leveled very precisely; nothing should wobble or protrude when the so-called "dry screed" (technically called prefabricated screed) made of wood chipboard or similar is installed as a load distribution layer.
The installation of wet screeds (at least not completely excluded by the preceding text) involves more problems than solutions from embedding thicknesses >80mm upwards.
Therefore, for this type of expansion, it is better initially to introduce a general height compensation, the cover plate made of MDF, covering, and then the wet screed.
With a complete system construction using prefabricated screed panels, one saves the "mixing water in the house," an aspect not to be underestimated when moving in is imminent.
Please remember that with a substructure of Ytong and installation with a wet screed, surface unevenness of the subfloor is no longer visually noticeable, but wet screeds must have as even a support as possible to ensure a uniform embedding thickness and to prevent length changes of the screed from being blocked on the back side (e.g., by steps between the aerated concrete blocks).
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Regards: KlaRa