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Dangers of Expansive Soil

By Elizabeth Elstien

Expansive Soil can ruin a home's foundation, yet few Illinois homeowners know about this soil type. A soil heavy with certain minerals and clay is known as expansive soil. This soil type absorbs more water than other soils. This heavy water absorption causes the soil to expand and shrink when dry. During expansion the over-wet soil lifts up on a home's foundation. When the soil is dry, the foundation settles in to the pocket caused by the swell-shrink phenomenon, in time causing it to shift.

Where is expansive soil found?

All over. States such as Arizona and Colorado are known for it. Illinois has expansive soils in areas such as St. Louis, St. Charles, Decatur and Springfield.

What problems are caused by expansive soil?

This soil type causes home damage first to the foundation/basement and then to upper levels. This soil has tremendous pressure when wet, so it is able to wreak havok on structures. The weaker foundation elements are hardest hit, such as slab floors. Damage to look for includes:

  • Cracks in foundation/basement floor.
  • Basement wall cracks and inward bowing.
  • Active foundation movement and/or upheaval.
  • Swimming pool movement and/or cracks to walls or floor.
  • Garage floor cracks or upheaval.
  • Brick, flagstone or concrete walkway/patio cracks or dislocation.

How can I tell if my soil is expansive?

A soil engineer can test the soil, send a sample to a reputable lab for analysis and give you a report. A less expensive method is to check the soil when dry for desiccation cracks, which make the dry soil look like puzzle pieces.

What can I do if my home is built on expansive soil?

If your existing home shows signs of structural damage described above, consult a structural engineer. There are several ways of slowing the expansion to protect the home or installing new foundation or garage slabs that are heavier and more resistant to soil expansion. Better drainage to keep the soils drier is also possible.

Should I build a new home on land with expansive soil?

It is possible. Construction techniques include wetting the expansive soil so it expands for building or replacing the top layer of this soil with a non-expansive soil type. Creating soil drainage to prevent excess moisture in the soil is another solution. Consult a structural engineer or construction manager for advice.

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About The Author

Elizabeth R. Elstien has worked in real estate for over 15 years as a real estate...

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