There are numerous underlying causes of foundation damage in the city, most relating to soil and weather conditions. We’ll discuss each of these in detail below.
Expansive soil is one of the leading issues causing foundation damage throughout the United States. While Forsyth County isn’t situated in the exotic soils of the Carolina terrane or Triassic basin, it does have a high concentration of clay. The ground in Winston-Salem is mostly comprised of Cecil clay loam, which is characterized by a high absorption rate, sub-optimal drainage, and expansion when it gets wet. It creates three significant issues for foundations in the area.
Most significantly, the clay soil in the city increases in volume as it gets wet. As the ground expands, it places excess pressure on your concrete slab and foundation walls, often causing inward movement and cracking.
The soil also loses volume when it dries, so it can shrink away from the concrete as moisture levels decrease. This process can create voids around and under your foundation, leaving sections of it without the support it needs to hold up your house. The concrete cracks and sinks into the earth as a result. If this soil movement happens at different rates across your property, your home will suffer from differential settling, which can quickly cause structural issues.
Lastly, clay readily absorbs and holds moisture, which means it will keep water pressing against your concrete for more extended periods than a silty or sandy soil. Longer exposure times to moisture often lead to damaging water intrusion and water vapor making its way into your under-home space.
Above-Average Rainfall & Drought
To make the problems with expansive soil worse, property owners in Winston-Salem experience above-average rainfall and regular periods of drought, both of which contribute to excessive hydrostatic pressure and differential settling.
The city experiences around 45 inches of annual rainfall, approximately 50% more than the national average. Excessive runoff soaks into the clay soil and causes expansion, and it also contributes to water intrusion and moisture issues in basements and crawlspaces. A large amount of runoff from rainfall in the area is an issue itself, but it’s made worse by the higher elevations to the east of the city in the Northern Mountain region.
Excessive runoff is dangerous for foundations, but a lack of rainfall is equally hazardous. Winston-Salem is prone to drought, which leaves soil dry and causes it to shrink away from the concrete under your home. Dry clay soil can leave your foundation without the support it needs to provide structure to your home, often leading to differential settling and foundation sinking.
The dirt in Winston-Salem is known to be acidic, which creates further complications for home foundations. Acids in the soil can erode concrete over time, leaving foundation walls or slabs weakened and potentially creating structural instability. After years of exposure, solid concrete walls can crumble or even collapse under your structure’s weight or the hydrostatic pressure from the surrounding soil.
Unlike many other parts of the United States, few North Carolina homes have full basements. Instead, a popular choice during construction is a partial basement or cellar, which decreases installation costs while providing the convenience of access to your under-home space.
These types of foundations mean sections of your home will be supported by different levels of soil. The clay in the ground swells and shrinks in response to moisture changes, which can vary significantly at different depths. As such, this common construction choice leaves homes in Winston-Salem at elevated risk of differential settling.
High Humidity Year-Round
Lastly, Winston-Salem experiences relatively high humidity throughout the entire year, averaging in the high 60% range in the winter and above 75% in the summer months. Humid air is an issue for all parts of your home, but basements and crawlspaces are at particular risk of moisture build-up, given their location underground.
Humid air outside can make its way into your under-home area, where moisture gets trapped. Damp air under your home can lead to mold growth, pest infestation, uncomfortable or contaminated air in your living space, and damage to construction materials under your home.