An ice dam is a problem of house and building maintenance on sloping roofs in cold climates. Ice dams on roofs form when accumulated snow on a sloping roof melts and flows down the roof, under the insulating blanket of snow, until it reaches below freezing temperature air, typically at the gutter where the cold zone is at soffit.  When the melt water reaches the freezing zone, it forms a dam, and snow that melts later cannot drain properly through the dam.  Ice dams may result in leaks through the roofing material, possibly resulting in damaged ceilings, walls, roof structure and insulation. A self adhered roofing membrane called ice & water installed under the roofing material helps prevent leakage from ice damming. This membrane can also help with wind driven rain.