The most global mistake of the developer can be improperly defined soil. In this case, the foundation will give you a lot of trouble. It is better not to take risks with this case and seek help from specialists. Do not forget about waterproofing. Its absence will probably lead to the fact that melt, soil and rainwater will fall on the walls of the foundation. As a result, you are guaranteed damp enclosing structures. The result will be very deplorable. They will rot and collapse.