The water stands on the sand plate

Our question now is, how do you fix the whole thing? Or do you let it dry as is and then repair the sand slab? And who bears the costs for the necessary measures? Should we as builders have protected the sand slab or is it the responsibility of the developer?

I assume you mean the sub-base, i.e., the cushion/preparation for the foundation slab?

First of all – you should not take any action yourself; this is the responsibility of your contractual partner. Whether any additional costs must be borne by you should be stated in your contract with your construction company. Mostly, it is contractually agreed that such costs are borne by the builders.

Construction expert on the go

Thank you for your answers. Yes, the compacted sand slab is the preparation for the foundation slab. Maybe we didn’t find much on Google because of the designation. I don’t find anything about it in the house construction contract. Only the generally usual agreement regarding the earthworks, that the construction company takes care of removing the topsoil to a depth of 30 cm as well as the creation of the sand slab to this depth and that any further work required is to be borne by us. Weather-related damage is not mentioned. Well, I will get in touch with our site manager tomorrow and report.

...and insofar as further work is necessary, it is to be borne by us. Weather damage is not mentioned.

That's quite clear, isn't it?