Yes, he now wants to go with 25cm WU concrete, doubly reinforced / armed. Exterior walls to be coated with at least 4mm bitumen thick coating instead of 3mm, to also cover load case 6: sealing against externally pressing water and rising seepage water. I just don't understand why they are so reluctant about the Weiße Wanne. In total, that should be cheaper than all the effort, right? The Weiße Wanne is also included in the construction performance description. So they must have built it before. The general contractor (GU) is also a local, very reputable company and enjoys an excellent reputation. I think they know their trade. Still, it surprises me that they always avoid the Weiße Wanne ("you don't need it, I wouldn't worry about it with this property," etc.) Instead, they also offered the Thepro basement (just search online). But I talked to them and they told me that with an exposed basement the system would not be helpful. Only for earth-contacting sides. So, in other words, I would have a transition somewhere to the half-exposed floor. So there must be something between the black tank and Thepro... Weiße Wanne? The topic is wearing me down...