Causes of Settlement
Incorrect grading near your home’s foundation, clogged gutters, short downspouts, and other drainage issues can all cause the soil supporting the concrete around your home to wash away or settle unevenly. Soil washout can leave voids underneath concrete surfaces, creating the ideal environment for the unsupported slab to sink and crack over time.
Extended periods of dry weather can also be problematic for concrete. Some areas of the country are rich in expansive clay soil. This type of soil expands in wet conditions and shrinks dramatically during prolonged dry periods. As the soil dries out and shrinks, the unsupported concrete may sink and crack.
An improperly prepared soil base can also be the culprit of sinking concrete. Before surfaces such as driveways, patios, and walkways are poured, the supporting soil must be adequately compacted to prevent washout and erosion. This should be done with a mechanical tamping machine for best results.