When silts, sands or gravels are contaminated with clay, however, heaving ability is usually much enhanced and becomes less predictable. At present the most reliable method of spotting a frost-heaving soil is to carry out a laboratory freezing test, although soils that show frost heaving in the laboratory do not always do so in the field. The test is therefore apparently on the safe side, but further research is required before completely reliable predictions can be made. Prevention of Frost Damage Frost heaving is not usually a problem in heated structures since the heat loss from the building keeps the temperature in the soil adjacent to the foundation above the freezing point. Difficulties often arise, however, in unheated detached buildings or in unheated additions to heated buildings.
Damage also occurs to roads, sidewalks and shallow underground service lines.
A detached unheated building located on frost heaving soil may show no signs of distress owing to the fact that the foundation has been raised uniformly so that no stresses have been induced in the structure. Because of the non-uniformity of soil and other factors such as variable snow cover, it is more usual, however, to have differential heaving. This may also occur where the building has supports carried on footings located inside the structure. Due to the protection provided by the building, the penetration of frost under the interior column footings may be less than that under the perimeter footings. Under these circumstances there is a possibility that differential movement will occur.