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

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

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

As already mentioned, if one does not see a possibility to waterproof a non-basement structure against soil moisture (W1.1-E or W1.2-E) with this soil structure, one will never do it. The required permeability coefficient that the soil may have is 10^-4 m/s (this applies to coarse sand/gravel).

If, for example, a foundation is laid over a gravel cushion, then there is a permeable subsoil to a sufficient depth. The design water level can be reduced and we have waterproofing according to W1.1-E (soil moisture).

I'll just give an example:
e.g. 90 cm frost protection material (F1 gravel)

- Frost safety is guaranteed (no frost skirts necessary)
- area-wide subsoil improvement (bedding modulus can be increased although it is already quite good in the report => possibly less reinforcement and no strip foundations necessary)
- Waterproofing according to W 1.1-E is sufficient

Before I would pay the additional 130 € per m² (really additional?), I would change the foundation or try it with drainage as recommended above.

Regards

VAT is passed on 1:1?! 100€ equity to 150€ sales price... that's rather unlikely to be passed on 1:1 I would probably take the slab from the house builder even if it's expensive, if you do something else they will always hassle you with the warranty because everything was due to the base slab or your idea I think

So, we had a callback from the house construction company yesterday. The costs are gross and there are additional costs. He didn't tell us much about the alternatives. Here we are supposed to call the [Bodengutachter] directly. The exact final costs are only possible after the structural analysis.

So, we had a call back from the house construction company yesterday. The costs are gross and there are additional costs. He didn’t reveal much about the alternatives. We are supposed to call the soil expert directly here. The exact final costs are only possible after the structural analysis.

That’s clear, of course they pass the matter on to the soil expert, because he has to bear the warranty that it works permanently like that.

So contact the soil expert and ask about alternatives. I’ve already mentioned a few bullet points to you. If nothing comes of it, I would perhaps get a second opinion. A new report costs around €1,000 and is thus cheaper than €18,000 additional costs. And I can tell you with 100% certainty that many other experts don’t even consider waterproofing according to W2.1-E.

: thank you very much for your reply again!

I spoke with the soil expert today and at the mention of drainage, new possibilities actually opened up. I was advised to inquire with the municipality. Said and done. They are no longer responsible, but the water board is. After calling there, I found out that it is allowed! The responsible employee is on vacation until Monday... The soil expert is now supplementing his report with the possibility of drainage. According to the soil expert, about 5000 euros in additional costs for drainage (?) instead of 22,000 euros for WU. That would of course be fantastic!

It would of course be great if it works out that way. I am glad that I could help. The only pity is that you have to approach the soil surveyor as a "layman" about such alternatives. You would actually expect something like that to be included in the scope of services. You can keep us updated on what comes of it in the end. Regards