There are a few underlying causes of foundation issues that are prevalent in the Columbia area. We’ll discuss these in detail below.
Much of South Carolina, including Columbia, is known for its Lynchburg soil, which is characterized by a high ratio of clay to other constituents. The clay-rich ground is referred to as “expansive soil,” primarily because it expands when it gets wet.
As the ground in Columbia gets wet from rainfall, the clay absorbs water rapidly and holds more moisture than typical soil. It can expand up to about 110% of its original volume, which puts immense pressure on your foundation.
The added stress can force your basement walls inward or your concrete slab upward, often resulting in cracking when the concrete can no longer flex. This stress is called hydrostatic pressure, and it can compromise your foundation’s structural integrity.
Columbia’s expansive soil also loses volume when it dries, which creates additional problems for foundations. During periods of dry weather, the earth can shrink away from your foundation. Even a small amount of movement can lead to severe foundation damage, as your concrete relies on the surrounding dirt for structure and support. If the soil dries too much, it can leave your foundation without the support it needs.
In a process called differential settling, the soil around and under your home can swell and shrink at different rates depending on drainage. Differential settling eventually leads to sections of concrete cracking and sinking to meet the ground again, meaning structural damage to your home.
Lastly, expansive soil in Columbia leaves homes at a high risk of water intrusion because it holds runoff against the concrete for extended periods. The longer moisture interacts with your foundation, the more likely it is to seep through foundation cracks or wick through the pores in the concrete, eventually making its way inside. Liquid water or water vapor in your basement or crawlspace can create significant issues for your home.
The rainfall in the area makes the problems with expansive soil even worse. Columbia receives an average of 48 inches of rain each year, about 150% of the national average. The city has also seen up to around 70 inches in a single year. Heavy precipitation is detrimental for foundations in any area, as it can easily seep through the concrete, leaving pooling water or moist air under your home.
Water can weaken your foundation over time, especially if it freezes in the concrete’s cracks or pores. It can damage building materials under your home, like floor joists and framing, ruin water heaters or other equipment you may have in your crawlspace or basement, and contribute to problems with moist air if it evaporates underside.
Water vapor can be equally as dangerous for your home, creating problems in your under-home area as well as moisture build-up in your living space.
In addition to excessive rainfall in the area, Columbia experiences high humidity for much of the year. Although some months in the area have an average relative humidity in the 50s, several months are at 70% and above. High humidity means moist air, which can spell trouble for foundations.
The air outside your home will inevitably affect the air in your crawlspace or basement, resulting in several problems. The first is that damp air typically stimulates mold growth. Mold can not only create musty odors or unsafe air in your house, but it can also damage concrete and other building materials. Specifically, wood floor joists and framing can rot and gradually lose their stability when exposed to moisture for long periods.
Additionally, moisture attracts insects and rodents. Of course, no homeowner wants to find pests under their home, but they cause severe damage to your property in addition to being a nuisance. Termites and carpenter ants destroy wood throughout your home, and rodents can leave feces behind that can be hazardous to you and your family.
The air under your home naturally seeps up into your living space in a process called the stack effect. This movement can bring humidity to your upper floors, often making the air feel colder in the winter and warmer in the summer. It can also lead to mold spores in your indoor air that can cause allergy symptoms for your family members.
The problems with high humidity in Columbia are made more of a threat to foundation and health because of the heavy rainfall, which can also contribute to moisture under your home.
Cyclones During Hurricane Season
Lastly, Columbia is prone to cyclones during hurricane season, which extends from around June to November. While the winds aren’t typically a problem for South Carolina homes, cyclones can bring heavy rains and flooding, which contribute to water intrusion, humidity under the house, and issues with expansive soil.