At this time of year, Chicagoland Concrete, Inc. receives many questions about the frost line and how it can affect poured concrete projects, including footings, foundations and flatwork. Wikipedia defines a frost line (also referred to as “frost depth” or “freezing depth”) as “the depth to which the ground water in soil is expected to freeze.” Footings, foundations and flatwork can be adversely affected by frost heave if poured improperly or at the wrong depth. If the underground sections of the supporting architecture are above the frost depth, the pressure imposed by the freezing and thawing of the ground water in the soil can result in cracked concrete which could end in considerable structural damage and consequently, costly and significant repairs to a home or project. Improperly installed concrete structures have been recorded to move or “heave” between three and four inches during a freeze/thaw cycle which can cause not only damage to the aesthetics of a project but also deterioration to the structural support. This can result in damage to the foundation which can lead to water issues in a basement or, worst case scenario, structural collapse.
Frost lines through the United States can vary broadly. For example, some of the Northern states have a frost line that can reach as deep as 60 inches while parts of Florida have no frost line at all. The Midwest portion of the country has a frost line that goes between 30 and 40 inches on average. Currently, the frost line in the Chicago area is recorded at 40 inches, which means that the water in the soil has not frozen at levels deeper than 40 inches below ground. In the Chicagoland area, building codes require that supporting structures are poured at least 42 inches below the ground; however, many architectural plans dictate digging to a deeper level to accommodate any future changes in the average frost line. When it comes to the foundation of your home, it is better to be safe than sorry.
We hope that this article has helped with some basic questions you may have regarding frost lines, frost heave and how it can affect your home or concrete project. If you have any further in depth questions, please feel free to contact the professionals at Chicagoland Concrete, Inc. in the office or via the website through the “Contact Us” tab. As always, please feel free to leave your comments on this post.