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Expansive soils

All major population centers on Colorado's East and West slopes are partially located on potentially swelling or expansive soils. These soils, popularly called bentonite, contain a clay mineral that swells when it gets wet and shrinks upon drying.

Swelling soils cause damage to thousands of homes every year. The extent of the damage varies from cracked driveways and sidewalks to severe structural deformation. Even well designed and constructed homes can be damaged if proper landscape installation and maintenance practices are not followed. There are several practices that will allow you to grow a landscape that complements your home, while avoiding the potentially damaging effects of swelling soils.

Begin landscaping with a site that has been graded for a positive slope so water drains away from the house. Consider planting vegetation no closer than five feet from the foundation, unless plants have very low water requirements. Xeriscape-type groundcovers and mulches are especially useful near houses because they can help reduce extreme moisture fluctuations.

Don't allow sprinkler systems to spray any closer than five feet from the foundation. And plant trees no closer than fifteen feet from the foundation. It's also important to carefully regulate water applied near the foundation. And avoid the temptation to remove downspout extensions to harvest water for flower beds near the house.

For more information, see the following Colorado State University Extension fact sheet(s).


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Updated Tuesday, November 19, 2013