Concord Carpenter

Roof and Gutter Heating Cable

By Robert Robillard on Home Maintenance

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Calculating the Cable Length

Once I have all that information, it’s time to calculate the amount of cable required.

The simplest way to figure out what you need is to take photos of the house and draw out the wiring pattern. When I do this, I do the following:

1. Measure the roof edge length
2. Measure the roof overhang
3. Measure the gutter length
4. Measure the downspout length
5. Take a photo of the roof. Send the photo to Warmup Inc. and they will design the system for you.

It’s also possible to design your own system if you prefer. To calculate cable length for purchase, I follow this formula:

1. Multiply the roof edge length by the spacing factor [see below] found on the Warmup Inc. website.
2. Choose the proper spacing factor, based on the depth of your overhang. I always round up if I have a size not listed.

Estimating Length of Cable

Roof Overhang   Heating width    Heating Height    Spacing Factor

12”                               2 ft                      18”                             2

24”                               2 ft                      30”                            3

36”                               2 ft                      42”                            4

3. Add in the total gutter length plus the total downspout length. In some cases, you’ll need to loop the cable down and back up the downspout in order to connect all the gutters around the house; remember, the cable is one continuous line. If you’ll need to do this, multiply the length of the downspout by 2.