How Does Freeze-Thaw Damage Concrete Foundations?

Concrete is naturally porous, meaning it has tiny spaces that can hold water. When rain, snowmelt, or groundwater soaks into a foundation, that moisture settles into the pores and tiny cracks. If the temperature drops below freezing, the water inside turns to ice.

Ice takes up more space than liquid water, roughly 9 percent more. That expansion pushes outward against the surrounding concrete with significant force. When the ice thaws, the pressure releases, but the concrete may have already cracked. Each freeze-thaw cycle repeats this process, slowly breaking down the material.

The amount of water the concrete is exposed to matters. Foundations with poor drainage, such as downspouts that empty next to the wall, stay wet longer and are more vulnerable. Soil that holds water against the foundation also raises the risk.

Temperature swings also play a part. Regions with many freeze-thaw cycles each winter cause more damage than areas with a single deep freeze. The quality of the concrete matters too; older or poorly mixed concrete is more porous and absorbs more water. Even the type of aggregate used can affect how much the concrete expands and contracts.

The right prevention is to keep water away from the foundation. Make sure gutters and downspouts direct water at least several feet from the house. Grade the soil so it slopes away from the foundation, and consider a drainage system if water pools near the walls.

Sealing the concrete with a waterproofing product can help reduce moisture absorption, but it is not a permanent fix. If freeze-thaw damage is already present, the pros may need to repair cracks and resurface the concrete. For structural issues, a structural repair specialist may be necessary to restore the foundation's integrity.