Several of the things that draw residents to Concord are also to blame for the high rate of foundation problems. We’ll explain each of the underlying causes of these damages below and the reason they’re so dangerous for your home.
Concord is situated on a soil variety called Clear Lake Clay. As the name suggests, the soil has a high concentration of clay. Clay soil is expansive, and it creates several issues for homes in the area.
The first problem is that it dilates when it gets wet. When precipitation soaks into the earth, the soil swells and places added pressure on your foundation. The expansion puts inward force on your foundation walls and upward force on your slab. This hydrostatic pressure is often enough to crack the concrete, leaving you with structural damage and an easy entryway for water into your home.
The second problem is more prevalent in Concord because of the naturally dry weather conditions. Expansive soil loses volume when it dries, so the soil around your foundation shrinks away from it during periods of little or no rain. The result is small voids forming around the concrete, sometimes leaving your slab without the support it needs and typically gets from the earth.
Unsupported sections of your home’s foundation can collapse under the weight of your structure if this settlement occurs unevenly. The resulting damage from this differential settling can be very severe and often requires structural repair.
The last problem with expansive soil is that it retains water for long periods between the tiny clay particles. Following rainfall or plumbing leaks, moisture is held against your foundation and has the opportunity to seep through cracks or pores in the concrete. Moisture problems and water intrusion are both an issue in Concord because of the soil’s absorbent qualities.
The lack of heavy and frequent rainfall is one of the climatic factors residents love most about Concord. The city experiences just over 18 inches of rain each year, which is approximately half of the national average.
The lack of precipitation throughout Contra Costa County leaves the soil excessively dry for most of the year. The extended periods of no rain make the risk of differential settling significantly higher.
The arid conditions punctuated by eventual rainfall create a dangerous cycle of dry and wet soil. The earth expands and contracts rapidly with the changes in moisture, and the frequent pressure and lack of support for your foundation during these changes can quickly create structural damage and instability.
California residents are perhaps the most familiar with earthquakes in the country because of the location on the west coast near the San Andreas fault zone. Concord, in particular, is affected by five fault lines that run near and through the San Francisco Bay area.
Earthquakes occur regularly in the city, and although most are small, even minor ground shifting can create problems. Quakes contribute to differential settling and can cause soil to shift and put undue pressure on your foundation.
Most homes in Concord are built slab-on-grade because of the very shallow groundwater. In slab foundation construction, it’s common practice to run plumbing lines through the concrete slab. Frequent minor earthquakes or more intense, isolated shaking in the area can rupture the plumbing lines and cause them to leak into the ground.
Plumbing leaks can cause several obvious problems, like water damage to your home and high utility bills. However, saturated clay soil under your property can cause foundation upheaval, which occurs when the ground under your slab swells and puts intense upward pressure on your concrete. This ground movement can cause massive damage and necessitate expensive structural repairs.
Lastly, flooding is relatively commonplace in Concord for a few different reasons. Tidal floods can occur during heavy rainfall or when tides are elevated from storm surge.
Tsunamis caused by earthquakes from the many faults near Concord can also raise water levels and lead to flooding. The clay soil in the city doesn’t allow runoff to drain through it readily, so any accumulation of water can be an issue for homes in the area.
Flooding contributes to soil swelling and hydrostatic pressure that can compromise your foundation’s structural integrity. It also increases the risk of water intrusion, as the absorbent soil will hold the moisture against your porous concrete for extended periods.