Thursday, December 1st by Tim Snyder
Known by different names (expanding soil, expansive clay soils, etc.), expansive soils can be found in many parts of the country, and these soils do billions of dollars of damage in the U.S. every year.
Sometimes referred to as expansive clay soil because of high clay content, this type of soil has some very distinctive characteristics. It shrinks and cracks when it dries out, sometimes cracking in a polygonal pattern. When it rains, the same soil absorbs water and expands, often with astonishing force. It’s this cycle of expansion and contraction that damages foundations. In expansion mode, clay-rich soil can exert over 5,000 lbs. of pressure per square foot on foundation walls. This lateral pressure can cause a foundation wall to crack, bow or tilt inward. Expansive soil located beneath a slab can cause the slab to crack and heave upward.
During dry spells, clay-rich soil shrinks away from foundation walls, footings and slabs. This can leave a void beneath a slab that causes the slab to crack and settle. Gaps between the soil and a foundation wall allow large amounts of water to enter during rainy weather, increasing the soil’s expansive force. Alternately, these gaps are sometimes filled with stone, additional soil and other debris that cause more pressure against the wall during the next wet expansion cycle.
Foundation Repair Contractors Can Overcome Expansive Soil Problems
A foundation repair specialist who is familiar with local soil conditions will probably know whether or not expansive soil has played a role in damaging a foundation. Since water is what makes clay-rich soil swell and shrink, one of the first things a foundation repair contractor will do is to check the function of gutters, downspouts and general drainage around the house. Moving water away from the foundation is a reliable way to limit soil movement, protecting the foundation from soil’s expansive pressure.
A foundation repair specialist may point out that soils rich in clay and silt aren’t just unstable; they also have poor load-bearing characteristics compared to soils that contain sand and gravel. If soil pressure has caused the masonry to crack and sink, the repair strategy sometimes calls for helical piers to be driven into the soil. The helical flanges (or plates) on these steel piers are shaped like the threads on a wood screw, and function in a similar way. As the contractor turns the shank of the pier, the helical plates pull the pier deeper into the soil. The contractor can add pier sections in order to reach stable soil beneath the damaged foundation. When the pier’s resistance to rotation reaches a predetermined level, the contractor knows that the pier is solidly anchored, and can provide the stable support the foundation has been lacking. A bracket is installed to connect the pier to the foundation; this can also enable the contractor to lift a sunken slab, footing or wall back to its original position.
Ayers' Basement Systems specializes in basement waterproofing, crawl space repair and foundation repair in Wyoming, MI and other surrounding areas. Visit them online for a free foundation repair estimate in Battle Creek, East Lansing, Grand Rapids, Holland, Jackson, Kalamazoo or in a nearby area.