Why Meet Frost Depth

By Nate Rogers, E.I.T. | May 30, 2020

As New Englanders, we are no strangers to dealing with snow, ice and long cold winters. When air temperatures drop below freezing, the ground is sure to do the same.

The frost depth (also known as “frost line” or “freezing depth”) is the depth to which the moisture content in the ground is expected to freeze during the winter. This depth varies by location since it is controlled by the local climate.

What does this mean for buildings? As the moisture in the ground freezes it can cause the ground to swell, a phenomenon known as frost heaving. Foundations, as well as pipes filled with water, can be moved or damaged from frost heaving if not properly accounted for. In general, the easiest construction solution is to build everything below the frost line.

An alternative to protecting a shallow foundation (and pipes) may involve using insulation in accordance with ASCE 32, Design & Construction of Frost-Protected Shallow Foundations. These options are often expensive and typically only considered on sites where shallow bedrock or other conditions make deeper excavations impractical. To find out the frost depth in your area, consult your local building code or give us a call! Whatever you build, make sure you start with a solid foundation.

2 thoughts on “Why Meet Frost Depth

  1. Richard

    We had to stop using posts like you show. In snow country, the frost will eventually break and heave the cements. We have started to use a “washburn” pier which is tapered so that when the frost grabs the pier then rises, it cannot get a hold on the pier and cause movement.

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  2. Michael Hippert

    Wish i took pictures, I pulled a deck down because the piers had heaved, some a lot some very little. The stairs and stair landings were far from level or safe. When I pulled the concrete piers from the ground, they varied in length from 12 to 60 inches. The shorter ones sunk deeper while some of the mid-length piers rose as much as 6 inches. The area where the deck was installed was kept clear from snow, I believe this will also cause the frost depth to be a little deeper because the snow is not insulating the ground.

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