Skip waterproofing in bathroom

[eestere]

After numerous debates with various EXPERTS, I've come to believe that if the waterproofing is skipped and the moisture comes from the "other" direction, i.e., from the outside, the tiles will come loose.

Can someone elaborate on this statement? True, false, depends, etc...

Keep in mind that our bathroom is above ground and the walls are stoneware in two layers, with an air gap in between filled with "kox," some kind of coal.

 

[jon_h]

No, that is not correct. At least the risk of tile detachment doesn't increase if you skip the waterproof membrane. What is probably being discussed is that plaster may detach if tiles are applied to it and the moisture level in the plaster then rises, especially if it is a weaker plaster. But this has nothing to do with the absence of a waterproof membrane. The adhesive can withstand being soaking wet all the time.

 

[eestere]

Sounds good!!

Admittedly, there is plaster on the walls, and unfortunately, I believe it's lime plaster since the house is from the 1930s and the plaster powders when you rub your hand back and forth on it. However, the color is not as white as I would associate with pure lime. Who knows, maybe they've mixed in cement or something... None of the people I've consulted with have been able to definitively say that it is truly lime plaster.

Before tiling, I was thinking of using plenty of something like primer so that the adhesive, or if it ends up being that, the waterproofing, adheres better. The risk of the plaster layering or detaching from the wall is small, according to my assessment, and using waterproofing gives me a more secure impression that the adhesive will stick much better to the wall if the waterproofing adheres better to the primer than the adhesive... Any tips?

 

[jon_h]

If it's lime plaster, it must be removed, as it rarely holds for tiling. To guarantee adhesion, the tensile strength must be 0.5 MPa in the substrate, which is equivalent to the weight of a midsize family car on the same surface as a 20x20 cm tile. This is, of course, not for the weight of the ceramics, but to ensure that the structure can handle the shear forces that occur when materials move with varying temperature and humidity. Primer does not solve this.

The waterproofing layer generally adheres worse than the adhesive on a given substrate. Waterproofing is not for the sake of adhesion.

 

[Robert Grönberg]

I don't understand how you think at all. It's not just the water in running form that causes moisture damage and mold infestation, but also the humidity, which becomes very high in a bathroom with a shower. Modern houses are not built the same way as older houses, where the possibilities for moisture barriers were limited. You definitely should not deviate from a moisture barrier in the wet area. It's like ignoring seatbelts because you probably won't crash anyway. The moisture in the air equalizes according to the principles of natural laws, i.e. nature ALWAYS strives to even out all types of irregularities. So moisture goes where it's less humid if there's no mechanical seal to prevent it. Then it could be that a house from -76 isn't so tight in the walls so the moisture stays. But I think you'll regret it if you don't install a moisture barrier.

/Robert

 

[jon_h]

No, it's not that serious. The moisture in the air is largely ventilated out, and a small part condenses on the walls to quickly evaporate and be ventilated out. It is extremely small amounts that can diffuse into the walls if the ventilation is working. This is shown empirically in all the bathrooms I've torn down that lacked any form of moisture barrier other than in the direct wet zones, where there hasn't been any signs of damage elsewhere in the room.

Additionally, the materials in the walls are completely inorganic in this case, so there is nothing that can be damaged, even in theory.

But as I wrote in the beginning, there is nothing to gain by skipping the waterproof layer either, so I can't see any reason not to follow industry regulations.