Some roof types are difficult to prevent ice dams from forming on. Ice dams occur when melted snow flows down your roof and under a blanket of snow on the surface of your roof. Heat could be leaking into your attic space from plumbing stacks, wiring, chimney, attic hatches, recessed lighting, or other areas. These leaky spaces are called bypasses and could be contributing to ice build up in your gutters and ultimately lead to ice dams. Finding bypasses in your home and insulating your attic properly can help reduce ice dams.