There are several underlying causes of foundation damage in the greater Pittsburgh area, most of which are related to the soil and the weather patterns in the area. We’ll discuss each of these factors below, including how each could affect your home foundation.
The most significant cause of foundation problems in Pittsburgh is the expansive soil. Much of the land throughout the city has a relatively high concentration of clay in the soil. Clay particles are tiny and drastically affect the soil’s drainage. The clay-rich earth in Pittsburgh presents several significant issues for homes.
First, clay expands when it gets wet, sometimes up to 110% of its original volume. Expansive soil is detrimental for foundations because it swells when exposed to runoff or floodwater.
The growing earth inevitably pushes against your foundation walls and slab, placing undue pressure on the concrete. With enough stress, your foundation will eventually give way and crack, leaving your home structurally damaged.
Another problem arises when clay soil dries out because it loses volume. When the water that caused the swelling drains deeper into the ground, the clay begins to dry and can pull away from your foundation. In a phenomenon called differential settling, the soil around your house can shrink at varying rates, leaving some portions of your foundation with support and some without.
Severe differential settling can cause areas of your concrete to separate from the rest of your foundation and settle further into the ground. As you can probably imagine, this leaves an unlevel base for the house above and compromises the structural integrity of your entire home.
Lastly, clay particles are fine and have very small spaces between them that can hold water. As such, the expansive soil in Pittsburgh readily absorbs and retains runoff and floodwater for a longer time than typical dirt does.
It can leave your foundation exposed to water for days after rainfall, leaving the concrete at severe risk of water intrusion or moisture-wicking. The damages associated with water or moisture under your home can be very costly.
Expansive soil can be dangerous in any part of the country, but it’s especially problematic in Pittsburgh because of the rainfall. The city experiences over 50 inches of rain each year, which is about 60% higher than the national average.
Rainfall is dangerous for foundations in Pittsburgh’s expansive soil because it keeps the ground wet and promotes soil expansion. The ground swelling means more stress on your concrete and a higher risk of foundation failure if the hydrostatic pressure becomes too much for your foundation to resist.
Regularly saturated soil also means your concrete will be exposed to runoff regularly, making the risk of water intrusion significantly higher.
The above-average rainfall and proximity to the Allegheny, Ohio, and Monongahela rivers leave Pittsburgh prone to flash flooding. Since clay soil readily absorbs water, the drainage in the city is generally very slow.
As such, water remains suspended in the earth for long periods. Flash floods make the problems with expansive soil significantly worse, as they saturate the ground, contribute to ground swelling, and put your home at severe risk of water intrusion.
Lastly, Pittsburgh has become increasingly popular in the past few decades, leading to an increased rate of development in and around the city. While new construction isn’t always correlated with foundation problems, some builders cut corners to speed up construction timelines, leading to several issues.
Before any foundation is poured, the ground needs to be extensively prepared to support the weight of the concrete and the house above it. Compaction of the earth after excavation helps maintain adequate support for your home, and it can limit the dangerous effects of ground swelling and differential settling.
Some builders in Pittsburgh may rush this step in an effort to keep up with the growing demand for housing, leaving even new construction at high risk for significant foundation problems.