Frost Heave Damage to a Foundation

In cold climates it is normal for the soil to freeze in the winter.  The depth of the freezing of the soil is called the frost line.  The colder the temperature, the deeper the frost line.  If the soil is relatively dry, the freezing does not result in much expansion.  But if the soil contains more water or has a source of water, there is more expansion.  This expansion due to water freezing in the soil is called a frost heave.

A frost heave will damage a foundation.  Since the top of the foundation wall is restrained by the wood framing, and by the bottom by the footer, the freezing, expanding soil will push on the exterior of the foundation wall with enough force to crack the concrete.

A horizontal crack will form on the interior of the foundation near the soil level.  The crack is not visible from the exterior.  A small horizontal crack will not typically result in enough displacement to lead to secondary cracks in walls or problems with doors or windows.  But the crack is a leak path for water and soil gasses, and with repeated freezing events, the crack can enlarge. 

Water seeping through a foundation crack can cause damage to drywall, trim or flooring in a finished basement, but the cracks will be concealed by the finished walls.

Since these horizontal cracks are caused by freezing water, they are a clear indication of a drainage problem next to the house.

For example, a home with no guttering – or clogged or leaking gutters – allows water to accumulate in the soil at the drip edge of the roof where a large area of roof drains.  The water freezes and pushes against the foundation.  Similarly, when there is landscaping water applied next to a home in the fall, residual water can remain in the soil into the winter when the freezing occurs.

Roof drainage and landscaping water must be managed to keep the soil next to the home dry.  Not only will this prevent frost heave cracks but will also prevent other water related deterioration of the concrete.

Foundation problems are always about water. Moving water away from your foundation is critical. Whether it's gutters with downspout extensions, hard surfacing or adequate slope, it's essential to keep the structure's footing dry!