Foundation slab impossible without a soil expert?

Hello everyone,

we had to add a lot of material, meaning the house will stand on an 80 cm layer of gravel and underneath partly up to 1.40 m of RC gravel. The guys compacted it excellently and performed a dynamic plate load test. Result: Evd= 37.3 MN/m2

The floor slab company (a big basement builder with K) is now refusing and demanding values for frost depth, bedding modulus, and stiffness modulus which apparently only a soil expert can calculate (???). I am now wondering why I need a soil report for a 2 m gravel layer? Can anyone help or is there really no way around it?

Best regards

Without being an expert, I can imagine that this is true. On the one hand, they have to provide a warranty, comply with the legal regulations, and on the other hand, you must have a basis to be able to assert warranty claims.

The company is unfortunately not entirely wrong. By the way, the pressure plate test must be conducted every 30 cm. The background, of course, is that someone guarantees that no settlements occur. Of course, you will also find a company that builds the foundation slab in this way because they "have always done it that way." But the risk remains, especially with these build-up heights. Just ask an office how much this costs. I think it will be in the low three-digit range.

I am wondering why I need a soil report for a 2 m gravel layer? Can someone help or is there really no way around it?

Who guarantees that the house won’t settle later and you won’t end up making warranty claims against the foundation slab builder? Of course, you can build with any run-of-the-mill construction company, but that’s like buying cheap = buying twice. Be glad that you have such a professional company on your side. I think it’s great how they work.

Hi everyone,

first of all, thank you very much for the quick answers. I already thought that it is a bit more complicated than I assumed. I was under the impression that the soil assessor looks at the natural soil and then makes a recommendation on how much gravel is needed on top so that it becomes frost-proof and stable enough. Since we have 2 m of gravel on top, I thought the soil no longer plays a role - so why get an assessment about it... It wasn’t about being petty, but rather about sensibility. Basically, that in this case the assessor probably wouldn’t do more than plate load tests, which actually have already been done.

Best regards

As far as I understand correctly, it is also important for the structural engineer, who is responsible for ensuring that the hut does not "tip over."
Edit: hehe, I just have to think of a quite famous tower. It was surely built without a soil survey. Most people know the result.
By the way, the tower is in Pisa.