Why don’t most builders in Texas, build basements? The answer is liability. Our soils in Texas are expansive and create problems not found in the northern states where basements are a common item.
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Soil is an essential component in the construction and stability of a house that is often overlooked by homeowners and homebuyers. Since the house is built on soil, structural damage to a house can occur if the soil expands, contracts or slides.
Expansive clay soils, Throughout the United States, particularly in Texas, California, Virginia and Colorado (though not exclusively in these locations), expansive or reactive clay soils are known to cause adverse effects on residential structures. Expansive soil expands and contracts due to changes in the moisture content of the soil, causing structural problems through differential movement of the structure. If the moisture content and or soil type differs at various locations under the foundation, localized or non-uniform movement may occur in the structure. This isolated movement of sections of the structure can cause damage to the foundation and framing, evidenced by cracking of the slab or foundation, cracking in the exterior or interior wall covering (indicating movement of the framing,) uneven floors and/or misaligned doors and windows. This type of movement is usually associated with slab on grade construction that is common in the previously mentioned regions of the country. However, this type of movement also occurs in structures with basements and crawlspaces.
A second effect of expansive soils is additional horizontal pressure applied to foundation walls found in basements and crawlspaces. Increased moisture in the soils adjacent to the foundation wall will cause the soils to expand and increase the lateral pressure applied to the foundation wall. If the foundation wall does not have sufficient strength, minor cracking, bowing or movement of the wall may occur. Serious structural damage to, or failure of, the wall may also occur.
A third effect associated with clay stone soil (a type of expansive soil) is the movement of soils on unstable slopes. Expansive clay stone soil, found as a layer under a more rigid top layer of soils, become unstable as the moisture content increases, allowing the clay stone and the top layers of soils to move. If the soil is located on a slope, the top layer of soil can creep (slow movement) down hill or even cause a landslide (sudden and dramatic movement). Consequently, a house with an inadequate foundation built on unstable slopes can be subject to creeping of the structure down slope, or to failure of the structure in a landslide
