A Therma-Roof system can help prevent ice dams and icicles by maintaining a continuous path for melt water to drain from the roof. As long as a heated path from the roof to a safe discharge area is maintained, ice dams will not form. The system can be used on roofs and valleys and in downspouts and gutters made from many types of standard roofing materials, including metal, plastic, asphalt and fiberglass shingles.
The Therma-Roof heating cable is laid in a "zigzag" fashion along the lower edge of the sloping rood. The heater should extend at least 12 in. (30 cm) above the level of the outer building wall, or 6in. (15cm) in above the snow fence, whichever is the higher, and extend down into the gutter. This will ensure a continuous run off path for melted water.
Since this is not a self-regulating cable, it can not overlap at any point!