Placing a layer of sand directly on top of native dirt or clay without proper mixing or transition layers often creates distinct drainage and moisture retention problems. Because water moves differently through coarse sand compared to fine-textured soil, a perched water table can form at the interface, impeding root penetration and causing root rot or suffocation for plants. Furthermore, heavy rain can wash fine soil particles up into the sand or cause the loose sand layer to erode away unless it is thoroughly tilled into the underlying soil to create a gradual textural transition or used strictly for specific construction and paving applications.