How to Determine the Frost Line for a Basement

As the winter air temperature drops below freezing, the water in the top layers of the soil also begins to freeze. If the temperatures stay cold for an extended period, the ice in the soil can go down several feet. The lowest level the ice is likely to descend to is called the frost line. A basement must have its foundations below the frost line to protect the home from ice freezing under the foundation and lifting the home up from the ground. Every area has its own frost line determination which must be followed for building construction. For example, Minneapolis requires footings at the 54- to 60-inch depth.

Instructions

1. • 1

     Check with the local zoning office or the public library to find a copy of the Residential Building Code for your specific area. If the state issues the building code, then look for information for your location within the book. Some government units are beginning to put the building codes on the Internet.

   • 2

     Ask the residential home building contractor who is building the home what the frost line is. He is required to submit to the authorities building plans for approval that follow the code.

   • 3

     Call the municipal building inspector to inquire about the frost line. He will be the one who issues the approval for the home building and inspect it afterward to make sure it has followed the construction code.