Construction of drywall partition / corner shower bathroom - moisture problem

Hello,

after water damage in the area of the shower (cause not clear), there is disagreement among my craftsmen regarding the "reconstruction" of the wall on how the correct build-up must be done to avoid consequential damage caused by condensation. The wall was previously constructed as follows ...

From the hallway to the bathroom:
Wallpaper|Drywall panel|Particleboard|Foil|Wood beams with insulation in the cavity|Foil|Particleboard|Drywall (green)|Tiles

The sealing to the screed and the wall was done diligently. The suspicion now is that due to temperature fluctuations during showering, moisture forms between the foil and particleboard (bathroom side of the wall) through "sweating," and swelling of the wall structure causes the joints to crack, allowing shower water to run behind the tiles as a consequence. This then leads to further damage.

What is the correct wall build-up for interior walls? Is it allowed to install the foil?

I would be very grateful if I could receive assistance. The work has not proceeded for some time.

Thank you very much.

What kind of membrane is this? However, the most important layer is missing from the described setup: a full-surface sealing layer made of liquid waterproofing (lastogum or similar), which must be applied both in the wall area and on the floor at least 30 cm beyond the water-exposed area. If it really was missing, the cause is clear...

A blue vapor barrier foil was installed as a membrane (I do not know the exact type). The shower area itself was coated (Lastogum). The corners were additionally sealed with a tape. Cracks have formed in the joints, allowing water to run behind the tiles and under the shower tray. The cracks presumably resulted from the swelling of the wall structure.

P. S. That’s what I meant by "The sealing to the screed and the wall was carried out diligently." ;-) Of course, full-surface.

That means the surface sealing was installed and is cracked? Has the house possibly settled?

The condensate on the vapor barrier seems very far-fetched to me. Maybe you can model your wall structure with the U-value calculator and play with the parameters to see when condensate would form in the wall. Just to get an idea of how realistic the theory is.

The surface sealing was not cracked. It even worked very well. The water ran behind the tiles under the shower tray and stood there. A humid environment ("only" humid) formed between the vapor barrier foil and the chipboard. If the protective coating had not held, the water would have run behind the wall.