Foundation damage can occur in any area of the United States, but there are several factors that leave Houston homeowners at higher-than-average risk.
Expansive soil is dirt that naturally has a high concentration of clay. Clay absorbs water more readily, meaning the ground retains moisture, and it expands when it gets wet. Houston and the nearby cities of Katy, Pasadena, and Sugar Land are afflicted with a high ratio of clay. In fact, Houston’s soil is referred to as “Houston Black” and is recognized as one of the most expansive in the world.
Expansive soil presents three severe problems for foundations. First, they readily absorb water during rainfall. Wet clay soil is heavy and expands in volume, placing immense pressure on your concrete block walls or concrete slab. As the pressure increases, foundations can bow inward and quickly crack to relieve the stress. These cracks can lead to structural instability in your home.
Second, expansive soils shrink in volume when they dry. Although the clay in Houston holds moisture for longer than typical Texas soil, it loses volume when it eventually dries and can pull away from your foundation. This process can leave sections of your foundation unsupported entirely. They tend to sink into the ground to meet the soil. When this happens at different rates across your home – in a process called differential settling – your foundation can crack, leaving an unlevel base for your house.
Lastly, expansive soil holds moisture for long periods after rainfall and expands to press against your concrete walls or slab. Liquid water from the ground that is held against the concrete often leads to water seepage into your basement or crawl space. This occurs readily through cracks, but water vapor can wick through undamaged concrete and evaporate into your home. This process can happen anywhere, but the clay soil in Houston makes it more common.
Like we just mentioned, expansive soil can contribute to basement water problems. This issue is made even worse by Houston’s wet season. The city experiences a dry season from around October to April and a significantly higher amount of rainfall from April or May to September.
The wet season in Houston commonly brings flooding and extensive ground swelling in response to the runoff. In combination with the city’s expansive soil, this type of weather often puts incredible pressure on foundations that results in cracking and rapidly worsening damage.
The wet season in Houston gives way to the dry season come September or October. The dry season is characterized by long periods of drought. Houston is considered to be at moderate risk of drought, and weeks without any rainfall are not uncommon.
Drought results in dry soil, and all dirt loses volume when the water evaporates out of it. However, expansive soil in Houston loses excessive volume when it dries.
Dry clay soil can shrink away from your foundation and leave portions of it unsupported.
Under this kind of pressure, foundations regularly crack and sink into the ground until they find support from the ground below.
The cycle of shrinking and expanding clay soil during the dry and wet seasons in Houston has a compounding effect that leaves foundations in the area highly prone to damage and failure.
Large tree roots in any area can grow into a foundation and put undue pressure on concrete walls or basement floors. This is a risk in Houston, but nearby trees present another issue: they soak up even more moisture than usual from the surrounding earth and contribute to the adverse effects of shrinking soil during dry periods.
Houston has experienced a housing boom in the past decade, which has done wonders for the local economy. Unfortunately, contractors in the area have taken some shortcuts to meet the growing demand for new homes. Rapid development in the region has resulted in poor soil preparation and compaction prior to foundation pouring.
Although no foundation in expansive soil is safe from problems, improper compaction during the construction process leaves the completed home at a significantly higher risk of foundation problems.
Additionally, the demand for housing has led to builders developing in areas that are unsuitable for construction, given the soil quality. In a regular market, building is often restricted to the highest quality soil based on foreseen issues with ground movement, but these are regularly overlooked when new construction is in as high of a demand as it has been in Houston. Couple this with expansive soil and drought, and you have a recipe for disaster.
Some Texas contractors offer a lifetime transferable warranty on their work, which often indicates that construction was done responsibly. However, these are less common in highly desirable areas, like Houston.