The building code requires a clearance between the stone veneer and the grade or ground level. There are several reasons for this and most of these reasons involve protection of the wall, not the stone! Behind the stone veneer is a drainage plane which was created when the weather resistive barrier was installed. The purpose of this plane is to collect and direct any water which squeaks behind the wall façade downward and out the base of the wall. If the base of the veneer wall is at or below grade, proper drainage will be impaired. Secondly, water which pools or collects at the wall base can rise into the wall through capillary action and enter the structure. Thirdly, if the veneer is in contact with vegetation (grass, plants, etc) growth into the wall is possible. Also, bugs and insects, including termites will find it convenient enter the wall system when the wall is in direct contact with earth. Finally, the stone is not designed to be continually wet or subject to the harsh chemicals found in soils.