ᐅ Construction of a Drywall Partition / Corner Shower in Bathroom – Moisture Issues

Hello,

after water damage in the shower area (cause unclear), there is disagreement among my craftsmen about the correct method for rebuilding the wall to prevent follow-up damage caused by condensation. The wall was previously constructed as follows...

From the hallway to the bathroom:
Wallpaper | drywall panel | particleboard | vapor barrier | wooden beams with insulation in between | vapor barrier | particleboard | green drywall (moisture resistant) | tiles

The sealing to the screed and the wall was carried out carefully. It is now suspected that temperature fluctuations during showering cause moisture to form between the vapor barrier and the particleboard (bathroom side) due to condensation, leading to swelling of the wall structure, cracking of the joints, and water from the shower penetrating behind the tiles. This then causes further damage.

What is the correct wall construction for interior walls in this case? Is it acceptable to install a vapor barrier?

I would be very grateful for any help. The work has been stalled for quite some time.

Thank you.

What kind of membrane is it?

However, the most important layer is missing in the described assembly: a fully bonded waterproofing layer made of liquid applied membrane (such as lastogum or similar), which must be applied both on the wall and the floor at least 30cm (12 inches) beyond the water-exposed area.

If this layer was really missing, then the cause is clear...

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

P. S. That’s what I meant by "The waterproofing between the screed and the wall was carried out carefully." ;-) Of course, fully applied over the entire surface.

So the surface waterproofing was installed and has cracked? Has the house possibly settled?

The condensation on the vapor barrier seems quite unlikely to me. Maybe you could model your wall structure with a U-value calculator and adjust the parameters to see when condensation would occur inside the wall. Just to get an idea of how realistic the theory is.

The surface waterproofing was not cracked. In fact, it worked very well. Water seeped behind the tiles and accumulated under the shower tray. A damp environment developed between the vapor barrier foil and the chipboard ("only" damp). If the protective coating had not held, water would have penetrated behind the wall.