There are several factors that create problems for home foundations in Wilmington. We’ll discuss these in-depth below and include some information on the type of damage each can cause.
Sandy Loam Soil
The soil in Wilmington is mostly Norfolk fine sandy loam and Portsmouth fine sand. All dirt is comprised of sand, clay, and silt. As the names of the soils in this area suggest, they both have a high ratio of sand to the other constituents. Typically, sandy loam soil is ideal for construction because it doesn’t swell or shrink as clay soil does; however, it can still be hazardous for homes built on it.
Wilmington’s soil has excellent drainage, but it is at risk of erosion as runoff moves through the earth. As such, water in the ground can erode portions of your property, sometimes creating voids or loose patches of dirt. Under the weight of your entire home, the soil can settle, leaving your foundation without the support it needs.
This settling can occur at varying rates under your house, leading to a process called differential settling, where sections of your home sink more rapidly than others. Differential settling eventually leads to areas of your foundation cracking and falling away from the rest of the foundation. It can cause severe structural damage over time, as your house relies on its foundation for a level and supportive base.
Ground erosion also occurs most readily where the earth meets your concrete, so runoff movement can create voids around your concrete block walls. Water can collect in these voids and be exposed to your foundation for extended periods, typically leading to water intrusion into your crawlspace or basement.
Wilmington experiences around 55 inches of rain annually, about 50% more than the national average. Heavy rainfall contributes to the issues present because of the soil content and risk of erosion.
More runoff means a higher chance of the ground around your foundation eroding, and it also fills the voids near your concrete more readily, leaving your basement or crawlspace open to water damage and moisture build-up.
The coast of North Carolina, including the Wilmington area, is open to hurricanes and tropical storms, experiencing an average of around two every year. While most don’t hit land, the wind and heavy rainfall can present a problem for your home’s foundation.
Rain can be detrimental to concrete, but excessive, concentrated rain that is common during tropical storms can be devastating over time. High rainfall in a short amount of time creates a higher risk of ground erosion, differential settling, and water intrusion, as it leaves runoff in contact with your foundation walls for extended periods.
High, Year-Round Humidity
Lastly, Wilmington’s high humidity causes moisture build-up that can quickly damage foundations and the rest of your home. The city experiences an average humidity between 70% and 80%, and while basements and crawlspaces are naturally prone to moisture issues, the humidity in the city makes the problem significantly worse. Moisture creates several issues for your foundation.
Since basements and crawlspaces are underground, they’re naturally cool and dark. Moist air in that environment creates the perfect conditions for mold growth. Mold in your basement not only decreases the quality of the air in your home via a process called the stack effect, but some strains can feed on the building material under your house. This can gradually weaken the concrete, floor joists, or framing that give your home structure and support.
Additionally, moisture naturally attracts rodents and insects. Pest infestations can be a nuisance to deal with, but certain insects can cause structural damage to your home. Termites and carpenter ants feed on wood and can destroy the framing or support beams in your house.