Base plate on special property, please note

Hello everyone,

We are planning to buy a plot of land in a new development area. Nothing has been built there yet. Construction start 2015.
The soil was replaced up to 4 m high due to contamination. Then sand was added again and each layer was compacted with heavy machinery. Residents could confirm this to us. Finally, topsoil was applied and compacted again. You can actually walk on it without sinking.
What do you think, does it make sense to build on it, or will the ground still settle so much that settlement cracks are likely? Should we expect additional costs for the foundation slab?
Best regards, Xinette

At our place, the building plot was prepared similarly. Former factory, up to 6m soil replacement (less in our case) and layered filling including compaction with heavy machinery.

The soil survey then provides the certainty of what additional measures need to be taken. If I remember correctly, the foundation slab then had to be reinforced with additional steel mesh and an extra layer of gravel had to be added. If everything had been calculated for us, it would have cost us all inclusive around 4,000€. However, I have also heard from builders in the construction area that they had to pay more because more soil had to be replaced.

You can actually only be advised to have a soil survey carried out (preferably before purchase). Only then will you know whether and to what extent additional costs for earthworks (e.g. soil replacement) or the foundation slab are to be expected. Of course, this also always depends on whether you want to build with or without a basement. Perhaps it would also be sensible to carry out a contaminated site investigation.

With us, the developer had to provide the responsible authority with proof/report that the contaminated sites have been cleared. Only then were the building applications processed.

At least the old contaminants are gone. Soil samples were taken constantly. We will see if there might be other samples as well. But I also think that despite solidification, there is a possibility of further settlement. Best regards Xinette

You need the soil report anyway, it's no big deal. Unfortunately, we couldn't have a soil report made before purchasing the plot and before signing the loan agreement. That was one of the big unknowns in our calculation.