Stockton is a hotspot for foundation problems primarily because of the unique geology and climate in the area. We’ll explain each of the underlying causes of foundation damage below as well as how each threatens your foundation’s structural integrity.
Expansive Soil & Claypan
The soil throughout Stockton isn’t uniform, but the majority of the dirt in developed areas has an abundance of clay in it. It’s referred to as expansive soil, and it has a high shrink-swell capability.
Stockton’s expansive soil is dangerous for foundations for several reasons.
The first issue with the soil is its ability to swell when it gets wet.
During periods of rainfall in the area, the ground absorbs an unusually high volume of runoff and retains it in the tiny gaps between clay particles. When the ground expands, it places excess pressure on your concrete slab and foundation walls.
The inward stress can be intense enough to crack the concrete, creating instability and necessitating expensive structural repair.
The second problem with Stockton’s expansive soil is that it shrinks when it dries, often losing all of the volume gained during rainfall. California is well-known for its dry summers, and during these long periods of little to no rain, the earth can lose all of the moisture in the upper layers that interact with your home’s foundation. The drying soil slowly shrinks around your home, causing your foundation to sink into the earth.
The clay soil often dries unevenly depending on the depth, which can lead to differential settling. As portions of your foundation sink at different speeds, sections can crack under the unequal pressure. The result is often massive structural damage and the potential for foundation failure.
The third and final problem with Stockton’s soil is that the clay particles retain moisture for long periods, meaning the ground drains very slowly.
Runoff easily gets trapped on or near the surface, contributing to flooding and the risk of water intrusion and moisture problems.
Much of Stockton is underlain by San Joaquin soil, which makes up a claypan at relatively shallow depths.
The clay pan is comprised of plastic, expansive soil that drains exceptionally slowly and holds moisture for an abnormally long time. This sub-surface claypan contributes to the issues with flooding and water intrusion.
Below-Average, Seasonal Rainfall
Stockton residents enjoy warm and sunny weather nearly year-round, with just 55 days of rainfall each year and virtually no chance of snow. The 21 inches of annual rain is just over 50% of the national average, and while this is ideal for enjoying the outdoors, it also contributes to foundation damage.
During the summer months with minimal precipitation, the ground around your foundation can dry completely, increasing the risk of differential settling beneath your home. To make matters worse, the winter months bring significantly more rain.
The wet-dry cycle that is common throughout the year in Stockton creates constant soil swelling and shrinking. The added stress on your concrete substantially increases the likelihood of foundation problems.
Earthquakes are a common occurrence throughout most of California due to the proximity to the San Andreas fault system. While Stockton is affected by this enormous fault, it’s also situated within miles of four other major fault lines, all of which contribute to the risk of ground shaking.
Earthquakes can cause immediate foundation damage if they shift soil into or away from the concrete under your home. They can create added stress that cracks the concrete and leaves you with structural damage.
Additionally, they can damage plumbing lines that are run through the concrete, a common design choice in homes that are built slab-on-grade.
Ruptured water lines can leak beneath your home, increasing the risk of differential settling and hydrostatic pressure on your slab. They can even develop massive ground instability that could compromise your foundation’s structural integrity.
Lastly, Stockton is prone to flooding. Tidal flooding from heavy rainfall or tsunamis caused by earthquakes can raise water levels throughout the San Joaquin River, causing an overflow. Additionally, concentrated rainfall in the winter can quickly back up to the surface, mainly because of the claypan and expansive soil that drains runoff very slowly.
Flooding saturates the earth and makes damaging hydrostatic pressure more of a threat. It also increases the chance of water leaking through foundation cracks or pores in the concrete and creating water and moisture problems in your home.