Several factors are at play in Yorktown that leave home foundations so prone to problems. We’ll discuss each of these below and provide a brief explanation of how they cause damage under your home.
While Yorktown’s coastal location makes the area desirable, it also means that the city is underlain by sandy soil. Norfolk sandy loam, Leonardtown loam, and Portsmouth fine sandy loam are the predominant soils in the developed areas of Yorktown, all of which are characterized by a high concentration of sand that drains water very quickly.
Rapidly-draining, sandy soil presents several two primary problems for concrete foundations.
The first issue is that sandy soil is very loosely packed, and the large sand particles have wide spaces between them that allow runoff to move through the ground rapidly.
As water drains into the soil, it can easily pull sand particles with it, frequently creating underground erosion. If the ground movement occurs around or under your home’s foundation, the instability can cause differential settling of the concrete and necessitate extensive structural repair.
The second problem with sandy soil occurs when the underground erosion caused by draining runoff creates voids against your concrete. This is a particular problem if your roof drains directly onto the ground or if your gutters overflow during heavy rainfall.
The voids can fill with water, and runoff can get trapped against the concrete for extended periods.
The longer your foundation remains exposed to moisture, the more likely it is to leak. Water and water vapor can seep through foundation cracks or the pores in the concrete. As a result, water damage, interior flooding, and elevated indoor humidity are all widespread problems for Yorktown residents.
Coastal Location & Flooding
Yorktown is situated on the coast and has an average elevation of just 13 feet above sea level. Many areas throughout the city are prone to coastal flooding when tides rise in response to heavy rainfall. Flooding can occur in the area even without heavy rain, so it’s a threat that homes are exposed to at all times.
The low elevation in the city means that the groundwater is very shallow. This is the precise reason that most homes in the area don’t have crawlspaces or basements, but it presents problems even for slab foundations. Shallow groundwater means that runoff has very little space to drain before it backs up to the earth’s surface.
During periods of heavy rainfall or flooding, your concrete at the surface is at greater risk of exposure to water. As a result, water intrusion and moisture accumulation are more likely. The minimal room for water to drain also increases the chance of differential settling once the runoff eventually soaks deeper into the ground.
Yorktown experiences over 48 inches of rainfall each year, which is more than one and a half times the national average.
The excessive rainfall in the region contributes to the problems with sandy soil because it increases the amount of runoff that can create underground erosion and differential settlement.
Flooding is also more likely because of the above-average rainfall, as the abundant runoff has little room to drain into the ground and can pool near the surface more readily.
The ground quickly becomes oversaturated in Yorktown, promoting water intrusion through your home’s foundation and underground erosion once the runoff does drain into the earth.
Tropical Storms and Hurricanes
Lastly, the coastal regions of Virginia experience excessive rainfall from hurricanes and tropical storms during hurricane season.
The concentrated rain from June through October promotes underground erosion, ground instability, and water and moisture problems in your home. Heavy winds from nearby storms can contribute to tidal flooding and further increase the likelihood of floodwater adversely affecting your foundation or the ground underneath.