NDSU Extension: Dry soil could cause problems for homes, buildings

North Dakota State University Extension
Drought can lead to a home's foundation cracking.

The drought not only affects crops and plants. It also may be causing problems for your home and other buildings.

“Sticking doors or windows and cracks in walls may be indications that the building is shifting due to soil shrinkage,” says Ken Hellevang, North Dakota State University Extension agricultural engineer.

As clay or other fine-particle soils dry, they shrink, creating gaps around the basement walls. This space exposes more of the soil to airflow, which increases the amount of moisture removal.

A gap along the wall may, through time, allow airflow that will dry the soil under the foundation. The foundation’s support is removed as the soil shrinks, which will cause the building to shift and may stress the concrete enough to cause a crack to form.

This also will occur around concrete slabs if the support base is clay or other fine-particle soil that swells and shrinks with changes in moisture content, according to Hellevang.

The gap between the soil and basement wall also allows water from rain to run down the wall and may result in water getting into the basement.

To minimize these problems, Hellevang recommends maintaining a relatively constant moisture content in the soil around the house or other building. Water the soil evenly and around the entire foundation during extended dry periods.

“Do not apply water directly into the gap because this may cause water intrusion into the basement,” he says. “Instead, apply water 1 to 2 feet away from the foundation edge. A soaker-type hose permits applying water to the soil without getting it on the house wall. Apply the water slowly, with rest periods of several hours, to permit the water to gradually soak into the soil to a depth of several feet.”

Sometimes people place plastic under rock next to the house as part of landscaping or to minimize water infiltration next to the house. This will prevent you from applying water next to the house.

However, water added to the soil even 3 feet from the wall will migrate through the soil profile and wet the soil near the basement wall. The water likely will not migrate enough to close the crack or gap near the surface, but it will wet the soil at greater depths and minimize the potential for soil movement to affect the structure.

“Do not fill the crack next to the basement wall with soil,” Hellevang says. “When the soil gets wet, it will expand, pushing on the basement wall, possibly with enough pressure to crack the wall.”

When the dry soil increases in moisture content, it will expand. Frequently, the expansion lifts the shifting building and may realign doors and windows. It also may impact the size of cracks in the building.

The size of cracks in the basement wall generally can be used to determine if the foundation or basement needs to be repaired by a contractor. Also, look for changes in alignment by sighting along the length of the wall to see if it is straight. Alignment problems are more common with soil expansion but can occur when the wall is not supported laterally due to the soil shrinking away from the basement.

“Cracks in the basement wall should be repaired to reduce the potential for water intrusion,” Hellevang says.

Because keeping the soil at a relatively constant moisture content is the goal, having a drainage system to remove excess moisture also is important. This includes making sure you have drainage pipe that’s encased in granular material along the footing and a drainage plane along the exterior of the basement wall.