Soil report for bungalow 140 sqm, additional costs for WU concrete?

Yes, gross or net is not specified. We requested a phone appointment so that we can clarify this.

We own the land and have made a contract with the construction company, so the latter.
Correct, we were more or less aware that the soil here is not optimal, we had spoken with another soil surveyor beforehand. Nevertheless, we made the soil report after signing the contract and built a buffer into the financing. It would have been better otherwise...

If I remember correctly, the sealing according to DIN for W2.1-E can also be done with bitumen and polymer bitumen sheets, plastic and elastomer sheets. Whether one wants that or the general contractor does it is another question. We chose WU, then it's settled. I can't say anything about the price.

Hi,
in my opinion, for a detached house without a basement, waterproofing against pressing water is only necessary if the floor slab is embedded in clayey soil at all four corners or if it is located in a flood zone.

Furthermore, according to the above specifications, you are building with strip foundations/frost skirts. This means that no water can get under the floor slab. Here it is only about rainwater/slope water/layer water and not groundwater rising from below.

If you install a perimeter drainage system, the water is caught beforehand and cannot reach the earth-contacting components. Thus, waterproofing against moisture in the ground (W1.2-E) is sufficient.
If drainage is not permitted, which unfortunately is often the case, then a surrounding gravel strip is simply installed.

It is basically only about ensuring a distance of 50 cm between the design water level (which here is the lowest point of the ground surface edge at the house) and the lowest waterproofing level (for moisture in the ground this lies on the floor slab). The design water level must, as described above, be reduced by geotechnical measures (drainage/soil replacement).

Unfortunately, waterproofing of floor slabs against pressing water is standard practice in some engineering offices and causes considerable additional costs for builders, although there is usually no reason for it.

Regards

Thank you very much for the very detailed answer! Then we will ask if a ring drainage is possible.

We had four drillings, one at each corner of the house. I have attached the 3rd drilling. They all look similar.

Is the 135 euros really only the SURCHARGE for the base slab? Or the total price?

You can save yourself the question with the craftsman about gross or net, craftsmen/companies always calculate with net prices, they don’t care about gross, because the VAT is passed on 1 to 1.

I don’t find the prices completely unrealistic. For a 4cm thicker floor slab we paid 11.50 EUR/m². For 25cm that would have been about 70 EUR. In the East, mind you, not Lower Saxony and with a fixed price at the end of 2021... You can easily add 30, 40% just because of location and current price developments. And it’s not done with WU concrete alone, there still has to be excavation, etc.

For a bungalow that hurts twice as much, of course, because the entire living area stands on the foundation... luckily for us it was "only" 97m²...