Many areas of North Carolina, including Raleigh/Durham/Chapel Hill have a high percentage of expansive clay soils. While sandy soils remain stable as water passes through them, soils rich in clay undergo significant changes based on their moisture content.
When clay type soils dry out, they shrink significantly (think of a dry sponge) -- so much that the ground can become covered with cracks, and load bearing structures can settle. But after the missing moisture is replaced by rain, the soil expands, the cracks are gone and the settled structure is pushed back, though rarely to the exact point it started. This is when structures can begin to twist or undulate.
Because clay soil absorbs so much water, it expands during wet weather, and that expansion can push both laterally and vertically.
Expansive clay soils can put enormous pressure on your basement, foundation piers or foundation walls. When the pressure becomes more than the wall can handle, the wall will begin to push inwards, or settle or lift unevenly. A licensed home inspector, licensed contractor or structural engineer can advise you on the severity of any movement, and what if any corrections are needed. A well-designed home constructed with good materials that has proper rain drainage (think grading, roof, gutters, downspouts) will keep the soils around the house from having a high fluctuation in moisture content. Builders in this area have been dealing with these issues for a very long time. With very dry and very wet seasons, some movement will occur, but the resulting cracks should be minor and will likely be considered cosmetic. Let the experts make that determination. And, yes, regardless of clay soils, this is one of the best places in the country to live â€¦. But then, thatâ€™s no longer a secret.