Moisture seeps through the floor-to-ceiling windows in the new building

At our place, the floor-to-ceiling windows were sealed from the outside with liquid plastic and fleece. This sealing was applied onto the bitumen thick coating of the basement wall and only then was the insulation added on top. The same applies to the front door and garage door.

Okay, thanks for the hint. I will point this out to the window installer again. Or rather clarify whether this even falls within his scope of work or if, for example, the shell constructor has to apply this bitumen adhesive membrane or black coating.

In fact, the sealing of the floor-to-ceiling windows as well as the doors is usually the work of a roofer. However, he should definitely coordinate with overlapping trades (plasterer or bricklayer if clinker) about the execution of the interface details. Especially in the area of perimeter insulation. Floor-to-ceiling windows in particular are often (I bet more than 50%) not sealed correctly. Just google "Der vergessene Anschluss".

In fact, the sealing of floor-to-ceiling windows as well as doors is usually the work of a roofer. However, they should definitely coordinate with overlapping trades (plasterer or mason if brick) regarding the execution of the interface details. Especially in the area of perimeter insulation. Floor-to-ceiling windows in particular are (I bet more than 50% of the time) often not sealed correctly. Just google "The forgotten connection."

What material is usually used for sealing over the perimeter insulation? Also liquid plastic? So from the window onto the bitumen thick coating and then again from the window over the insulation?

At our place, the floor-to-ceiling windows were sealed from the outside with liquid plastic and fleece. This sealing was applied onto the bitumen thick coating of the basement wall and only then was the insulation put over it. The same applies to the front door and garage door.

That is correct. And I always recommend doing it yourself. Only in this way is it guaranteed to fit 100%. It will cost you a maximum of 2 afternoons.

You don't need a bitumen thick coating if it's a WU basement.

Thank you very much for all the previous answers. I took another picture of the "outside" yesterday. As I understand it, no sealing tape needs to be applied here anymore by the window installer, as is the case everywhere on the inside, right? Instead, I have to create a proper seal here with liquid plastic and fleece that extends a few centimeters over the corners. Basically, I have no problem doing it myself if the window installer or roofer washes their hands of it... It is just important to me that it is properly sealed in the end, because of course, we don’t want moisture in the house that might only become noticeable after years.

Thank you very much for all the previous answers. I took another picture of the "outside" yesterday. As far as I understand, no sealing tape needs to be applied here by the window installer anymore, as is the case everywhere on the inside, right? Instead, I have to create a proper seal here with liquid plastic and fleece that also extends a few centimeters over the corners. Basically, I have no problem doing it myself if the window installer or roofer refuses... It is just important to me that it is properly sealed in the end since of course we don’t want moisture in the house that might only become noticeable after years.

Isn’t that the window installer’s job? Mine only pointed me to it..... The roofer has to/can do it.