New building with basement | WU concrete plus ring drainage

Why the additional costs is a good question! According to the cost estimate, the drainage of the partial basement (approx. 50 m²) costs around €4,000 and the seepage shaft at about 6 meters deep an additional €8,000.

Maybe we were offered the drainage particularly cheaply (I don't believe it!), but €4,000 just for drainage when the system can be installed in the open basement pit seems very expensive to me.

Since the basement is in glacial till, drainage without a seepage shaft doesn't make sense, right? The water can't drain away. The water from the roof goes into the sewer system.

Correct, but in my opinion there are two other possibilities here:

1. you can check if you can get a discharge permit for drainage water into the sewer system (provided this is technically feasible in terms of elevation)
2. you can consider using a cistern instead of a seepage shaft and store both the drainage water and the rainwater from the roof there. It should not cost much more (if at all), and you would probably have more benefit from it.

WU basement, do nothing else. You can skip the drainage. Capillary action reaches up to 10cm, the wall must be at least 20cm thick.

Thank you very much, Jann!

I spoke again yesterday with the expert who created the soil report. The problem with the soil is apparently that the clay layers have very poor water permeability. Therefore, water would seep from the surface toward the house and press against the house wall. With WU-Beton (WW), this is apparently not a problem, but special attention would need to be paid to tightness at the window shafts and house entrances, as the water infiltrates very slowly. However, he also said that with WU-Beton (WW) without drainage and soakaway pit, it is quite possible that condensation occurs inside due to the temperature difference, since the water pressing from the outside can cause a refrigerator effect.

In general, one would also need to take care of the water beneath the normal floor slab (partial basement), as it can also accumulate there during heavy rain.

Regarding the costs, the masonry basement with black tank and drainage/soakaway pit is slightly more expensive than the WU-Beton version with drainage/soakaway pit.

Therefore, we will probably decide on this variant.

Hi,
when it comes to the basement, I would never even consider anything other than WU.... if they even minimally slack off on the black tank, you will be dealing with damp basements for ages.

Drainage is actually unnecessary for a WU basement (note that there are still differences between a WU basement and a white tank), but given the terrain situation, I might consider it after all. But first, check your BP, is drainage even allowed? Often you are not even allowed to connect an emergency overflow to the sewage system. That can become problematic. In the worst case, you have to expect your house to be completely underwater, which definitely rules out the black tank.

Regarding ventilation, yes, definitely connect the basement to the ventilation. Additional costs are minimal and you can potentially design some basement rooms without windows.

Best regards,

Andreas

I built WU Keller (weisse Wanne) and installed the drainage under the basement shafts which then lead into the cistern. This way, the cistern does not need to be installed as deep. The basement is still dry after 20 years (partly used as a residential basement).

Thank you very much for your opinions.

Since we really have no idea, we are most likely the perfect "cash cow"!!
We are building with a cistern, where the roof is connected. I just thought that you can't feed the "surface water" there, as sediments are carried into the cistern and it becomes more polluted. But now that I think about it, cleaning the cistern is the cheaper option than the soakaway!