One problem brought about by the expansion of water on freezing has occurred in cold store buildings. This is frost heave, the name given to the damage caused to the buildings when the water in the subsoil beneath the site freezes and expands, causing
upward bulging of the floor and damage to foundations and walls. This reached serious proportions about the mid-fifties as storage conditions went lower in temperature. The trouble is now prevented by installing a heater grid of insulated stainless steel wires on the concrete site of the building during construction. Fed from the low-voltage output of a step-down mains transformer, a power of about 13.5 watts per square metre in the grid keeps the concrete a few degrees above freezing and provides for the inevitable “slow continuous flow of heat upwards into the cold store. The heater grid itself is covered with a 25 mm layer of cement and sand above which is a thick layer of thermal insulation on which the cold store floor is laid.