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How Does Frost Affect A Foundation

Feb 9, 2018 • By Matthew Stock with Todd Bunge.

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Living in the Midwest means living through the changing of the seasons. Who doesn’t enjoy the warmth of spring to break the back of winter or the crisp air of fall as leaves are changing colors? Having four seasons also means dealing with severe temperature swings from blazing hot to freezing cold. Humans have the ability to dress and prepare for these changes. Buildings and permanent structures do not. Your house is built with a foundation buried underground in soils that are porous, like a sponge. Different types of soils expand and contract at different rates when water is in them. In the summer, dry weather can result in soil shrinkage. In the winter, water trapped in the soil can freeze. Water expands when it freezes so the soil also expands. These constant cycles of expanding and contracting are the reason foundations fail.

Freezing Ground

With the exception of extremely dry conditions, most soil is going to retain moisture. In the winter time, snow falls, melts and soaks the soil. It gets cold at night and the ground freezes. The soil around your house freezes at the top first. As the cold continues, the ground continues to freeze deeper and deeper. As the ground freezes below layers that are already frozen, the expanding water pushes upward, resulting in what is called frost heave. This condition is usually seen on sidewalks, driveways and patios first. As time goes on, this up and down motion can create cracks or settling.

These affected areas then need to be lifted to become level again. But soil doesn’t always lift upward. If confined, it will also expand side to side, putting pressure on the foundation. In cold areas, building codes require the foundation to be installed below the typical frost line for that region. Most foundations are required to be at least 36” below grade but the deeper the better. Older homes built on shallow crawl spaces commonly have foundation problems as a result of freezing ground.

Foundation Issues

As you can imagine, years or decades of soil expanding into a foundation will have an impact on the structural integrity of the concrete or cinder block. In concrete walls, cracks form as the wall is pushed beyond its limits. Water then enters the home if the crack is wide enough. A common DIY repair is to put epoxy, cement or spray some of that late night sealer in a can on the crack.

Although this may seem to be a good fix, water is still entering the crack from outside and, when it gets cold, freezes inside the wall. Now the small crack is working on becoming a larger crack. Crack repairs need to be done correctly by injecting them with polyurethane. This prevents water from entering the crack altogether.

Another common problem is when pipes are drilled through the wall to get to an addition, lamp post or garage. Freezing ground is working on these pipes, up and down, weakening them until they fail to seal at the wall or even allowing water to enter the pipe. As we all know, water and electricity don’t mix and it could create a very hazardous condition. It can also happen to water, gas and sewer lines. Sealing inside and out of these pipes is required.

Foundations made from cement block are actually more at risk from damage by frost. To understand why, you have to look at the way a cement, or cinder, block wall is made. Block walls are made by stacking hollow blocks on top of one another with cement or mortar in between them. While they hold up very well to pressure applied from the top pushing down, the weight of the house structure, they are not very strong laterally. Think about building blocks when you were a kid. Stacking them up you could stand on them but it didn’t take much to push them over. Cement block foundations work well in the south where there isn’t the risk of freezing ground expanding into the foundation, wanting to push it in. Most older block foundations in this area show some kind of damage. The most common is tipping where the top three or four courses start to bulge inward. A line is commonly seen at this joint indicating the shift. If allowed to continue it can get worse and require bracing or, worse yet, straightening.

What can I do?

Once your foundation has damage, it needs to be repaired. Cracks need to be properly fixed but it takes a trained eye to see the story the foundation is telling. To help keep this damage from happening, preventative steps can be made to help your foundation. Water management is key to a foundation’s health. Moving downspout water away from the foundation by using underground downspout extensions. Take a close look at the grade around your house. Are there areas of ponding water than can be re-graded to direct water away? Can yard drainage be installed to help move water to a better location? Even installing mulch can help give the ground a bit of a blanket to reduce how much frost develops.

If you would like one of our foundation and water management experts evaluate your home, schedule an appointment online or give us a call to set up a free estimate.

Tags: structural foundation repair, foundation damage

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