Foundation damage generally occurs because of soil consistency, weather, and construction practices. All three of these contribute to problems for property owners in Cary. We’ll discuss each of these factors and how they affect concrete foundations below.
Cary is located predominantly in Wake County and partially in Chatham County. Both counties are located in an arc of exotic soils unique to North Carolina and the immediately surrounding states. This arc has two distinct sections, referred to as the Triassic basin and the Carolina terrane. Cary is located in the former, which is characterized by an abundance of clay in the soil, believed to have been deposited by glacier movement hundreds of millions of years ago.
Clay-rich soil is more absorbent than dirt with a lower concentration, so the soil in this arc is referred to as “expansive.” It grows in volume when it gets wet and loses volume as it dries. Expansive soil creates several problems for Cary foundations.
The most significant issue is the growth of the soil during rainfall. As the ground swells in response to runoff, it puts added stress – called hydrostatic pressure – on your foundation walls and concrete slab. The pressure is often enough to bow the concrete inward and eventually crack it. This type of movement can quickly compromise the structural integrity of your home.
Another major issue arises when the expansive soil in Cary dries. When it loses volume, it can shrink away from your foundation and leave voids under or around your concrete. Your foundation relies on the surrounding soil for stability, and these voids leave sections of your foundation unsupported. This process, called differential settling, can cause the concrete to crack and sink into the earth if it loses too much support from the shrinking soil.
Lastly, the clay in the soil holds water against your concrete for long periods after rainfall, with added pressure as it expands. When the water suspended in the ground interacts with your foundation, it can get forced through cracks or wick through the porous concrete. This process is referred to as water intrusion, and it can lead to water damage and moisture problems below your home.
Above-Average Rainfall & Drought
Cary experiences above 45 inches of rainfall each year, which is about 50% more than the national average. Water and foundations don’t mix well, so Cary’s heavy precipitation contributes to issues under the home.
Properties in any part of the United States can experience water seepage and related damages during rainfall, but Cary is at particularly high risk because of the amount of rain it sees and the expansive soil in the area. Not only does consistent runoff contribute to problems with hydrostatic pressure, but it also increases the chance of water intrusion.
Too much rain is a problem, but not enough moisture in the soil can be equally as damaging. When expansive soils dry out, they retract from your foundation, failing to provide adequate support for the concrete. As we mentioned above, parts of your foundation can crack and sink into the ground until they meet the soil again.
Cary and much of the northern parts of North Carolina are at moderate risk of drought. Even if the area doesn’t experience record-setting droughts as it did in 2007 and 2008, shorter periods of dry weather can contribute to the differential settling problems discussed above.
Many homes in Cary take advantage of multi-level foundations, such as partial basements or cellars. These split foundations are somewhat uncommon in many parts of the country, but the convenience and lower cost of installation, when compared to a full basement, have led to their prevalence in North Carolina.
The levels of these foundations are supported by soil at different depths, and the problem with them arises because ground settles mainly based on moisture content. The earth at an eight-foot depth swells and shrinks much less readily than soil supporting a slab-built on-grade.
As such, multi-level foundations are prone to differential settling, regularly leading to cracked and sinking sections of your home and the associated structural damage.
High, Year-Round Humidity
Lastly, North Carolina has relatively high humidity and a high dew point, both contributing to an above-average level of moisture in the air. Humidity can be detrimental to any part of the home, but basements and crawlspaces experience moisture problems more readily.
Cary’s elevated humidity contributes to a wealth of related problems under homes in the area, including mold growth, damage to foundations and other building material, warping of floor joists and framing, and an increased risk of pest infestations.