Building on clay soil can be a risky endeavor. Clay, with its high reactivity to moisture, can pose serious challenges to construction projects. However, with the right knowledge and techniques, you can successfully build on clay soil without breaking the bank. In this article, we will explore what clay soil is, its properties, and how to build a foundation on this unpredictable ground.
What is clay?
Clay is a type of soil that exhibits specific characteristics. When wet, it becomes soft and sticky, and when dry, it hardens. Compared to other soil types, clay has the finest particles, which contribute to its physical properties. The presence of water molecules surrounding clay particles gives it high plasticity.
Properties of clay soil:
- High plasticity
- Reactivity to water
- Swelling and contracting
- Stickiness
- Heaviness when wet
- Brittleness when dry
The composition and local climate can significantly influence the characteristics of clay soil on your site. Therefore, it is crucial to obtain an up-to-date geotechnical report to ensure the success of your construction project. Without proper techniques, you may exceed your budget and face delays.
What are the different types of clay?
Clay soil can be classified based on its mineral composition and plasticity. The mineral composition varies by color and geographic location. For example, Texas clay soil is known for its dark gray to black color, while clay soil in Hawaii is commonly red.
Here are the seven clay types defined by the USDA:
- Silt: 80% or more silt and less than 12% clay.
- Sandy clay loam: 20-35% clay, less than 28% silt, and 45% or more sand.
- Clay loam: 27-40% clay and 20-45% sand.
- Silty clay loam: 27-40% clay and less than 20% sand.
- Sandy clay: 35% or more clay and 45% or more sand.
- Silty clay: 40% or more clay and 40% or more silt.
- Clay: 40% or more clay, less than 45% sand, and less than 40% silt.
To accurately determine the composition of your clay soil, it is essential to conduct soil testing. However, you can make an initial estimation based on nearby geotechnical reports. Additionally, a quick on-site test involves taking a handful of soil and rolling it in your hand. If the soil can be shaped into thin spaghetti-like shapes, it indicates a higher clay content. If the soil crumbles easily, it means there is less clay.
Where is clay soil commonly found?
Clay soil is prevalent in many regions, but Texan soil, in particular, has a high clay content. The Blackland Prairies, covering over 15 million acres and stretching from San Antonio to north of Dallas, are known for their clay-rich soil. In this area, you are likely to encounter rich and dark clay soil, which contributes to Texas’ ranking as the top state for foundation problems caused by expansive soil.
Building a foundation on clay soil
Building a foundation on clay soil requires special consideration to protect it from the constant expansion and contraction caused by moisture. Without proper protection, your foundation may suffer significant and expensive damage over time. However, this doesn’t mean that building on clay soil is impossible or doomed to failure.
One effective method to mitigate the risks of clay soil is to use an above-ground foundation system like the Wafflemat System. This foundation design is specifically engineered to withstand the frequent expansion and contraction of clay soils. The system utilizes empty cavities on its underside to absorb the soil’s movement, providing a stable foundation.
For the best results, it is always recommended to consult with a geotechnical engineer who can provide expert advice based on your soil type and project specifications. Additionally, you can find valuable insights from experienced engineers in the field who have dealt with similar soil challenges.
Remember, building on clay soil requires careful planning and expert guidance. With the right approach, you can successfully construct a safe and sturdy foundation.