Pole Barn Footings and the Frost Line
Frost can damage a pole barn building and cause it to lean. It is therefore essential that footings be inserted in the ground below the frost line.
During the winter, the ground freezes from the top down. The depth of the frost line, or how far down the ground freezes, depends on the type of soil, the severity of the winter, the amount of water in the soil, and the depth of snow that acts as insulation. In a northern climate, the frost line can be 60 inches deep or more, while in a southern climate frost might not be an issue.
Water in soil collects and freezes into “ice lenses,” which are thin layers of frost. When it freezes, water expands. Ice can exert 50,000 pounds per square inch of pressure on footings that are embedded in the ground. This process is called frost heave. It is strong enough to lift even a large building.
If a building is lifted by frost heave, it might not return to its original height when the ground thaws because dirt can fill in under the footing when it is lifted. Over time, the building can start to lean.
If columns treated with pressure preservatives are not embedded deep enough in the ground, or if they are encased in concrete in conical holes that are wider at the bottom than at the top, they are prone to the effects of frost heave. It is therefore essential that footings be embedded below the frost line. Before you build your pole barn, check with your local building department to find out what the frost depth is in your area.
Heavy clay soil doesn’t drain well, so it is more susceptible to frost heave than sandy, well-drained soil. Even if the footings are deep enough, ice lenses can form on the wood and concrete and lift the pole barn footings and posts from the side. This can be prevented by increasing the diameter at the bottoms of the holes.
When you are ready contact CHA Pole Barns to talk about your pole barn project.