A layer of sand should be in the range from 40 to 50 mm, after the laying process, the sand should be well compacted. Mandatory should be checked for evenness, while the construction level is used.
In the case when the sand is laid on the weak soil, it is recommended to lay out geotextiles in 2 layers, the first is laid until the crushed stone is laid, the second is after.This is how the bearing capacity inherent in the foundation increases.