Raising the floor in a bathroom on a concrete intermediate floor

[Viktorcloetta]

Hello, I'm considering building a bathroom where there used to be a wooden floor on top of a concrete subfloor, with a basement underneath. I'm wondering how I should fill the 250mm gap below because I assume I can't keep the old joists underneath due to the bathroom's waterproofing requirements.


Thanks in advance

 

[vanpire]

EPS concrete maybe? Depends on how big the bathroom is.

 

[Viktorcloetta]

Maybe it is, the room is 14 square meters. Another problem is how much the floor can support, so I'm hesitant to throw in too many tons.

 

[Tiger79]

Eps cement doesn't weigh much...

Do you need to fill up 25cm?

Can't you have a step down into the bathroom?

 

[Viktorcloetta]

Eps concrete weighs 450 kg per cubic meter. But can you fill with foam plastic or something similar and then float with leveling compound?

 

[Tiger79]

It becomes around 100 kg per square,

 

[Stefan1972]

why can't you have battens under the waterproofing layer?

 

[Jonatan79]

Add regular insulation and place chipboard on top, then sealing layer, etc. Make sure the beams are close together, preferably 30-40cm cc.

 

[Viktorcloetta]

Doesn't moisture accumulate between the concrete and the waterproofing layer? It would have been absolutely easier with a wooden frame.

 

[Jonatan79]

Why do you think that? Many houses are built just as I described. Even my own.

 

[pelpet]

Cellular plastic + EPS concrete + a thin layer of self-leveling compound should work. Alternatively, self-leveling compound directly on cellular plastic. I can't say exactly how thick each layer should be, but maybe 20 cm of cellular plastic and 5 cm of self-leveling compound?

Remember that cellular plastic is cheap, but EPS concrete and self-leveling compound are expensive.

I wouldn't have used a wooden frame in a bathroom if it can be avoided. If there were moisture problems, the inorganic construction would tolerate moisture much better.

 

[Stefan1972]

Of course, it is like that, but there are bathrooms in houses made entirely of wood too, so I don't really see the problem.

 

[pelpet]

If there is a problem with the floor drain, which is the most common failure in a wet room, a wooden structure is much more affected by moisture from a leak than a concrete structure. If the bathroom is flawless, there will of course be no problems, regardless of the type of construction.

 

[Stefan1972]

Yes, I understand the point, but it seems far-fetched to try to exclude wood just because it rots more than other materials. In that case, all bathrooms would be built in prefab concrete boxes if the surface layers are that bad.

 

[pelpet]

I might have expressed myself a bit differently. I didn't mean to dismiss wooden frames as a whole but thought it's a deterioration to introduce wood now when there is already a fine concrete slab.