How the Type of Soil You Have Can Affect Your Foundation

Whether you’re building a new home or searching for a place to move, location is everything. You’ve spent hours, days and maybe months evaluating a property, making note of the surrounding amenities and how close it is to your work. One thing you’ve probably never considered is the type of soil around the foundation.

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Before you finalize your decision on your dream home, make sure you understand the common types of soils and the foundation issues each can cause.

Foundations on Sand, Silt and Clay Soils

Sand, silt and clay soils are found close to bodies of water, including along riverbanks, lakes and ponds and in the coastal plains. Often referred to as expanding soils, compacted sand and clay soils tend to absorb moisture during storms and then shrink when they dry out. The constant expansion and shrinking of the sand, silt and clay soils put homes at risk for cracks and shifts in the foundation. It can also cause expensive structural damage, such as:

• Sinking floors: When sand, silt and clay soils expand and shrink, they result in uneven floors. You may have noticed this in older homes where certain rooms tend to bow in the middle.

• Cracks in the foundation: When clay soil shrinks significantly, the movement can put stress on your floors and walls, causing large cracks to develop. Depending on the size of the cracks, large amounts of water can seep in, causing flooding and personal property damage.

• Drainage issues: Because clay tends to retain moisture and absorb large amounts of water, it can lead to pooling in your crawl space or basement.

Sandy Soils

Sandy soil is made of sand and gravel with large particles that can shift and move, leading to instability, and it's typically found in warmer climates, such as the desert, along beaches and near riverbeds. This type of soil doesn’t shrink the way clay soil does, but it’s still not the best choice for supporting a foundation.

• Erosion: When water travels through the sand, it can cause large gravel pieces to shift, leaving gaps below your foundation as well as erosion. This erosion can cause poor soil conditions and decayed vegetation surrounding your home.

• Settlement issues: Shifting soil can cause sinking floors and leave cracks in your home’s foundation. These cracks can spread to walls and floors, resulting in expensive foundation repairs.

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Loamy Soil Around the Foundation

Loamy soils are found in warmer climates, especially floodplain areas. This type of soil has a high bearing capacity and is rich in organic matter. Typically dark brown or black in color, loamy soils contain sand, silt and clay and provide the best support for homes. Like other types of soils, loamy soils can still cause issues:

• Organic matter breakdown: Organic materials break down over time. Because loamy soils contain high levels of organic materials, shifting issues can occur when this matter decomposes.

• Water retention: Organic materials have a high water content. When organic matter decomposes, water is absorbed into the soil surrounding the foundation, which weakens the foundation.

Gravel and Rock

Gravel and rock soils are usually found near creeks and rivers. The larger pieces of stone provide high levels of stability for home foundations and offer excellent conditions to build on. This type of soil also drains very well, preventing flooding and other water-related issues. Some of the common foundation issues with gravel and rock soil include:

• Maintenance: While not really an issue, gravel and rock soil may require some routine upkeep in order to maintain structural integrity. The smaller gravel segments can shift but can be filled in with foundation fill dirt as needed.

• Construction issues: Depending on how rocky the soil is, it may be hard to dig into if you’re planning on a basement or excavating soil for gardening. This can lead to uneven ground during landscape grading.