Then you risk it

Further, on the basis of the results of geological studies, the designer will calculate the depth of the foundation.

This depth depends mainly on two factors — the level of groundwater on your site and soil type. And if you lay the foundation above the given level, especially with a high level of groundwater and in the presence of fluffy soils, then you risk it that your foundation will squeeze out of the ground when frosts will come out of the earth.