Roof and Gutter Heating Cable

By Robert Robillard on Home Maintenance


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


  1. 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.
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About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

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