Base slab vs strip foundation

What would never be frost-free if it concerned the ground-level slope

It always depends - but if neither the slope nor the soil is load-bearing, then gravel would only be good for the earthworks

The difference actually lies in the static system. With appropriate soil, the strip foundations do not require reinforcement but can transfer the loads directly into the ground. The slab foundation then only receives light constructive reinforcement. It is different with the load-bearing slab. Here, the loads must be completely transferred through the slab, meaning the slab becomes a load-bearing component and is usually heavily reinforced.

20cm gravel under the slab...

Hello

I see the 20 cm as a capillary-breaking layer.

Steven

Exactly like that! It was solved that way with us too. Capillary-breaking gravel layer and strip foundations