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Soil Types and Their Effect on Your Foundation

Soil can make or break a home’s construction. Different soils have unique properties, which can affect how your home's foundation is supported.

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Your home’s foundation is the pillar that supports your entire household. As such, it should be built properly and on stable ground. If the soil under your home is not stable, the foundation may crack, sink, or worse; the entire building could collapse. Knowing what kind of soil sits below your foundation and its characteristics allows you to catch problems in your foundation even before they arise.  

Properties of Good Construction Soil 

Good soil for building should have the following characteristics: 

  • Balanced chemistry and neutral pH to prevent it from rusting other construction materials 
  • Stability through the wet and dry seasons so that expanding soils do not crack foundations 
  • Strength under pressure so that the weight of the building does not cause it to sink into the ground 
  • Excellent ability to capture precipitation, so that runoff and erosion do not damage the structure 

It’s important for you as a homeowner to understand various types of soils as well as their different properties. 

Types of Soils 

Soils are classified according to their texture, engineering properties, and how they relate to foundation support and site development.  Their strength and stability depend on their respective physical properties. Some common types of soils include: 

Man-Moved Soil 

Sometimes, builders have to extract soil from one location and move it another site for construction purposes. Such soil is known as man-moved soil. While these soils reduce wastage, they may not have the load-bearing capacity required to support entire structures. 

If you choose to build on man-moved soil, you must compact the ground first. Poorly compacted soil tends to compress below the house’s weight, creating settlement problems that can damage your structure.  

Backfill Soil 

Construction projects typically require a vast amount of digging, mostly for foundation work. Eventually, once the foundation is poured and your home is built, the empty space around the structure is filled with the backfill soil. Backfill soil is used to strengthen and support a structure’s foundation while promoting better water drainage. The type of fill soil you chose for this purpose can help ensure that your home remains standing for many years. Some common backfill soils include: 

  • Coarse-grained soils: They’re fairly common and are made up of gravel, sand, or a mixture of both.  
  • Fine-grained soils: These soils are finer than other soil types, but have poor drainage properties. When they’re compacted, they do create a firm base to build on. 
  • Crushed rock: This type of backfill provides a compacted base and is used in the construction of driveways. Its filler characteristics also make it an ideal material for projects where drainage is vital. 

Native Soil Layers 

These are naturally dense and hard-packed virgin soils found at the site of construction. They include: 

Clay: Clay is expansive, meaning it expands in wet conditions and contracts in dry weather. This expansion and contraction can cause cracks in your home’s foundation or walls and may even result in uneven floors. To increase stability, clay soil foundations have to be dug deeper into the ground. 

Sand and gravel: This type of soil is composed of large particles, which allow the soil to drain water quickly. This feature makes sand and gravel suitable for construction. Because they retain less water than clay, sand and gravel are less likely to cause a building to shift. Compacted sand and gravel offer even more stability and are a great option to build a foundation on.  

Bedrock: Bedrock lies deep down in the earth and has a high bearing capacity. Unlike clay soil, which shifts and expands, bedrock is more stable and resistant to water damage. Structures built on top of them are less likely to move or settle.  

Loam soil: This type of soil is made up of sand, clay, and silt. It combines the best of each soil type’s qualities to create the ideal balance for supporting a foundation. Loam soil generally does not shift, expand, or contract drastically and handles the presence of water exceptionally well. 

If you suspect that the soil underneath your home’s foundation is weak or unstable, call the experts at Foundation Recovery Basement Systems to schedule a free inspection and repair quote. We will examine the foundation and tell you what type of solution you will need to stabilize your foundation.