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Soil types for building

Updated February 21, 2017

Whether building a new home or a smaller outdoor structure, check the soil before building for stability. The soil your structure is built upon is its first foundation, and some soil types are more prone to expansion or shifting than others are. If the ground beneath your building is unstable and shifts or expand, it can cause your structure to shift, creating cracks in the walls and foundation problems.

Rock

Solid rock, such as crystalline bedrock, bears the most weight of any type of soil, making it one building option. According to the Concrete Network, crystalline bedrock can handle up to 5443kg. per square foot of load-bearing pressure keeping the structure stable. Other types of rock, including sedimentary, can bear up to 2722kg. of pressure per square foot. However, some types of sedimentary rock, such as shale, are not always a safe option on which to build. In time, sedimentary rock can break apart, causing the ground to shift beneath your structure.

Gravel

Although gravel soils can only bear up to about 2268kg. of pressure, according to the Concrete Network, gravel soils, which typically feature a mixture of earth and bits of rocks or larger pieces, are often a solid, soil type for building. Unlike pure rock soils that may shift as the rock breaks,, gravel soils are created from a mixture of soil and rock that has already broken down. Gravel soils tend to stay in place and react well under pressure. They also are typically well drained.

Coarse Soils

Coarse soils, like sand, are often stable building spots. Sand doesn't expand when wet. It's also difficult to move, making it one of the most stable soil choices on which to build. Due to the nature of the soil, sand can only bear about 3,000 to 2268kg. of pressure per square foot. When evaluating sand for building, look at what's mixed in with the sand. Gravelly sand or basic sand is stable, but sand mixed with more unstable soils, like peat or clay, usually is not a good building option.

Other Soils

Fine-grained soils, such as clay and silt, are typically not stable soils on which to build. Silt shifts easily, and clay expands when wet, often creating cracks in any foundation built upon it. Organic soils, such as peat in the process of decomposing, are also not stable for building, as the organic materials are often not fully compacted or settled. In some cases, organic soils are mixed with other soil types, such as sand, making them more stable.

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About the Author

Sienna Condy began writing professionally in 2001 while attending the University of Cincinnati, and she's been at it ever since. Since graduating, she's written everything from marketing materials to articles on removing stains. Today, she enjoys writing about weddings, legal issues, science, health and parenting.