Icicles are caused by a process known as ice damming, commonly found on the drip edge of homes and other buildings. This occurs when there is enough heat escaping through the roof to cause the snow that is on the roof to melt into water and run down the roof only to freeze at the unheated section known as the drip edge. The more heat leaving the home through the roof deck, the worse the ice dams get. This is a sign of a poorly insulated attic. The ice can even curl the shingles up and get underneath the shingle. When that ice melts, it goes directly into the home in most cases, ruining sheet rock, blistering paint, and causing mold problems with the framing of the home.