What Is the Frost Line in North Carolina?

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As of 2014, the frost line depth for the majority of North Carolina is 6 inches. The extreme southeastern coastline has no seasonally frozen ground. Frost lines are often referred to as frost depth or freezing depth.

Local frost line depths are important to know when doing construction, as many counties have building codes that determine when building or digging may take place in areas with seasonally frozen ground. One regulation states that water mains must be buried beneath the frost line depths or insulated if installed above the depths to prevent the pipes from freezing and busting. A building’s foundation must also be set below the frost line to allow for frost heaving. Frost heaving occurs when the ground freezes and swells upwards; it may cause major damage to a building’s structure if the building’s foundation is not deep enough.