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Basement Water Infiltration: The Basics

Water infiltration is a concern for many homeowners. Water can push up under the foundation at the seams between the floor and the wall, or through cracks in the walls themselves. These conditions are often due to a high water table, hydrostatic pressure, and the normal shrinkage of concrete.

In geological terms, the water table is the level below which the ground is saturated with water. A water table will rise and fall throughout the year, depending on the amount of rain or snow. A high water table is often found in low-lying areas and areas where the soil does not drain well.

Andrew Timp, President of the Existing Homes Division at Quality Waterproofing, often sees the repercussions of a high water table under St. Louis homes.

“Practically,” Timp explains, “a water table resembles veins of water, or an underground stream. If that water gets too close to the surface, then homeowners are looking at standing water, or even flowing water under their foundation.”

During times of heavy precipitation, the soil underneath a home will become saturated with water. More susceptible homes will experience water pushing up through cracks and weak points in the floor, or even push over the foundation of home with high grading. However, there are multiple factors in water infiltration.

“Even if a house next door is experiencing basement water infiltration, this does not mean that the home in question is experiencing the same issues,” says Timp. “Every home is different.”

Another common reason for water infiltration is through the normal shrinkage of poured concrete. Shrinkage cracks can occur as the poured concrete dries and cures. These types of cracks appear more frequently if the concrete was mixed improperly, cured rapidly, or if control joints were omitted. Eventually, concrete may shrink enough to create cracks in the foundation that allow moisture to come through. While prone to leaking, usually shrinkage cracks are vertical in nature and are less likely to suggest structural damage.

Horizontal cracks, however, are typically tied to structural damage. As such, horizontal cracks have the potential to be more serious. Structural cracks can sometimes be due to high hydrostatic pressure from oversaturated soil and poor yard grading. Bowed walls that seem to push into the basement is a sign of structural stress – and need to be addressed immediately. Bowed walls may require wall stabilization to prevent further damage. 

Even a small amount of water infiltration can be costly to a homeowner, as incoming water can destroy framing, carpet, drywall, and baseboards. Water infiltration left alone can produce mold and mildew, which pose serious health concerns.

“Noticing cracks as they form becomes crucial,” says Timp.

Check regularly for cracks in the basement walls, and moisture along the seam between the wall and the floor. Even basements that are finished can be inspected for signs of extra moisture, which may signify a leak somewhere in the foundation.

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