There are several things present in Apex that contribute to foundation issues. We’ll explain each underlying cause below as well as how each causes damage to the concrete under your home.
Expansive soil is an issue in many parts of the United States, but there is a high concentration in Apex. Geologists have found an arc of exotic soil in North and South Carolina that is believed to have been deposited there by glaciers hundreds of millions of years ago. The arc has two distinct sections called the Triassic basin and the Carolina terrane. Much of Apex falls within the former. The soil in the Triassic basin is unique to the surrounding area in that it contains a high accumulation of clay. Clay soil can quickly destroy a foundation’s integrity in three ways: by swelling, shrinking, and retaining water. Clay soil expands when it comes in contact with water, meaning that the ground in Apex swells each time it rains. The growing earth puts added pressure on your concrete slab and basement walls. Concrete can flex slightly in response, but it eventually gives way to the stress and cracks. As such, expanding soil can compromise your home’s structural integrity. The reverse is also true of clay soil: it shrinks when it dries. Precipitation eventually soaks into the earth, leaving the ground around your home to dry and lose volume. The dirt can pull away from your concrete, creating voids around the foundation where your home is then unsupported. Under the stress of your house’s weight, the foundation can sink into the ground. When this settling happens uniformly, your house is more or less unphased. However, the ground typically dries at varying rates under and around your concrete, causing differential settling. This uneven movement can cause structural damage very rapidly. Lastly, the clay particles in Apex’s soil are tiny and easily trap water between them. The ground generally retains runoff for long periods after rainfall, leaving your concrete exposed to moisture for days between precipitation. When water is in contact with your foundation for an extended time, it’s more likely to seep inside through pores or tiny fissures and create moisture buildup and water damage under your home.
Above-Average Rainfall & Drought
Expansive soil is dangerous for foundations in all areas of the United States, but the climate in Apex makes the problems more widespread and significantly more hazardous. Apex receives an annual average of over 46 inches of rain, which is nearly 50% higher than the rest of the country. Heavy, concentrated rainfall leaves the ground more prone to expansion, meaning your foundation will face additional stress from the soil outside. Additionally, the heavy rain creates excessive runoff. The clay holds runoff against your porous concrete for longer than typical sandy or silty soil, leaving your home at higher risk of water intrusion. Much of North Carolina experiences drought, which intensifies the issues associated with shrinking clay soil. Although the drought in Apex is rarely severe, even days or weeks without rainfall can allow the ground to dry entirely. The frequent cycling between swelling wet soil and shrinking dry soil makes differential settling a more common problem.
North Carolina homes are commonly built with multi-level foundations, including partial basements and cellars. This design adds living or storage space to your home, but it can leave your structure more prone to differential settling. The earth naturally dries at varying rates depending on depth below the surface. Multi-level foundations rely on two different depths for support. When the soil below the shallow portion of your house dries more quickly as runoff drains into the ground, it creates differences in the earth’s shrinking and settling properties under your structure. This can contribute to differential settling, which often eventually leads to severe damage.
High, Year-Round Humidity
Lastly, Apex has a year-round humidity of between 65% and 75%. The air’s high moisture content lends itself to several problems for basements and crawlspaces in the area. When humid air seeps into your under-home area, the moisture gets trapped inside. High humidity under your home can contribute to a myriad of issues, including water damage, mold growth, and pest infestations.