How to Install a Heat Cable on a Shingle Roof

Climb up to the roof and measure the areas to be covered with heat cable. Beginning by a window or roof deck door, measure a maximum of 6 feet for connector cable that will plug into an electrical outlet. Run the cable across the ridgepole and down the outer edge of one side of the roof to the bottom edge.

Along the bottom edge of your roof, plan a row of zigzags 18 inches high and 18 inches wide. If your roof does not divide easily by 18, bring the bottom points of the zigzags closer together, keeping the intervals between them even. Once you have finished calculating one side of the roof, double your figures except for the connector cable. This will give you enough cable for both sides of the roof.

Check your measurements using a manufacturer's chart. Allow for the height of dormers, measuring the height of both the walls and the roof against the roof. Double the length of cable needed for any downspouts located in the middle of a run of cable; cable will need to run down, then up to where you continue across the roof. Double-check your calculations by completing a manufacturer's diagram or drawing your own.

Check the outside temperature before installing your cable. It should be at least 50 degrees Fahrenheit. Lower temperatures can make shingles brittle.

Thread cable over the roof following your diagram. Starting at the end you need to plug into the electrical outlet, use enclosed clamps to attach the cable to shingles as you turn corners around dormers or zigzag along the roof. Clamps will either clip onto the bottom edges of shingles or pinch through them. Some brands of cable include spacers, which help hold the cable straight without clamping it down. Clamp the heat cable securely but do not damage the cable covering or bend the cable at sharp angles. Both actions can damage the cable.

Position the water/temperature sensor as described by manufacturer's directions. Different brands use different sensing equipment, so follow the directions for your current installation.

Plug in your heat cable and monitor its performance during the first heavy storm. Make any minor adjustments needed before it snows again.