Calgary has a very harsh and unique climate with winter temperatures that swing up and down rapidly causing conditions that are very hard on concrete. One of the common occurrences in fluctuating climate regions is the dreaded “Frost Heave.” This unfortunate phenomenon is caused by moisture buildup under concrete, which then freezes, expanding and “heaving”, leaving an ugly mess and spiderweb cracking throughout your concrete slab. Concrete also expands and contracts with temperature fluctuations, so the rapid, sometimes extreme, temperature changes can also lead to extensive settling and cracking of large spans of concrete.

Frost Heaves Covered Under Warranty

Most concrete companies do not warranty frost heaves or hairline cracks in the slab and may only warranty for surface flaking, which occurs when they over work the surface and or use too much water. Often concrete companies will only warranty for cracks that are more than two feet long and greater than 3/16” wide, but this is limited to exclude cracks caused by frost heaves.

Protecting Your Property From Frost Heaves

Your best chance of avoiding these unpleasant results in your garage is a frost wall. Frost walls ensure that moisture does not saturate under the concrete, protecting your slab from the consequences of extreme weather conditions. While attached garages are automatically built with protection to keep out the frost and ice, frost walls are important to consider when building a detached garage in Calgary. Adding a thicker gravel base and more rebar may help keep cracking down to a minimum, because the spaces between the gravel allow for some movement of moisture under the solid concrete.

Determining if the Cracks are from Frost Heaves

If you want to know if cracks in your concrete are caused by frost heaves there are two things you can try. First, find the point where all the cracks run and meet and then place a marble on the concrete. If the frost has heaved up the marble will roll away from the centre of all the cracks in each direction respectively. Secondly, take a hammer and tap around the edges of your garage; it should sound very dull and solid. If you then tap the middle of the slab and hear a hollow noise, you’ve got frost heaves. As the frost heave melts it leaves behind a hollow void under the concrete.

If your garage, driveway or patio is suffering from frost heaves, there is a solution. Cut along each of the cracks, opening them up to about 1/4”, and then fill the voids with non expanding grout. You will see the difference in colour and material, but after a couple of coats of concrete paint it will look like brand new!