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Roof and Gutter Heating Cable

Roof and Gutter Heating Cable

Warmup Roof Ice and Snow Melting Cables

Some homes are predisposed to ice dams – and the leaks that can result from them. Lack of insulation, warm air leaks, and complex roof designs all contribute to ice dam formations. Preventing roof leaks requires addressing these issues and ice dams themselves, but that’s not always easy to do. This article will address roof and gutter heating cable.

Ideally, you’d be able to go into the attic and insulate the roof from the inside; but often this is too expensive or invasive, especially if the attic or underside of the roof is not easily accessible.

In this case you have two choices. You can treat the symptoms by using a roof rake to remove the snow every time it snows, or you can treat the root cause and install roof and gutter heating cables.

What Is An Ice Dam Leak?

An ice dam is a ridge of ice that forms at the edge of a roof (also called an “eave”) and prevents water from draining off the roof. Ice dams occur after a snowfall and get bigger after several days of freezing temperatures.

An ice dam leak occurs when water builds up behind the ice dam, works its way back up and under shingles, resulting as a roof leak.


How Does House Heat-Loss Create an Ice Dam?

The heat from the house travels to the underside of the roof surface in three ways:

Example of air leak in attic

This heat melts the snow on the roof and the melted water drains down the roof, under the snow. When this melted water reaches the roof’s overhanging edge it freezes the water, forming a dam.

This blocked or “dammed” water then pools, backing up the roof and resulting in a roof leak. Ice dam leaks cause costly damage and can become a health problem if moisture trapped inside the house causes mold to grow.

Roof Ice and Snow Melting Cables

Homeowners often don’t have the budget to fully insulate their attics, and they often don’t want to deal with the hassle of a full-scale roof renovation. In these situations, I advocate installing a roof and gutter heating cable system.

I use a company called WarmUp Inc and use their Warmup Roof Deicing Cables. These self-regulating cables work with “smart” controllers and sensors to melt snow and ice, allowing water to drain from the roof. The system prevents the ice from forming a complete dam and keeps a drain path open for water to drain off the roof, and through and out of gutters.

While this roof and gutter heating cable system does not completely cure ice dams, it does prevent ice dam leaks and subsequent damage. The goal is to get the water off the roof and through the gutters before it refreezes.

Using Snow Melting Cables

Warmup ice and snow melting cables can be used on all types of roofs, including:

Design Your System

When I’m looking at a client’s home, I often start by looking at locations for the outdoor electrical junction box and system controller.

Some of the factors in this decision involve the following:

  1. Electrical requirements: Ensure that the house can accommodate a 30 Amp breaker. This typically accommodates 300-400ft of cable and completes a typical residential home.
  2. Locate the starting point of the cable in an area that is best accessible from the power location. I want my cable power connection to start at a UL Listed weatherproof junction box.

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.

Wire Pattern On Roof

The roof and gutter heating cable is installed in a triangular or saw-tooth pattern. The spacing of the loops should be at 2-foot intervals.

It is super important that the cable run from the overhang and extend up and into the heated section of the roof. This means the cable MUST travel past the intersecting line of the exterior wall and the roof.

Rule of Thumb: Extend the cables high enough to pass the house exterior wall by approximately 6 inches.

Pattern for Valleys

A roof valley is where two intersecting roofs meet. These areas see a lot of snow accumulation and roof drainage and create perfect conditions for massive ice dams.

If a valley exists in a problem area of your roof, install the cable up and back down the valley a minimum of 3 to 4 feet. Remember to add this cable length to your measurements.

Securing the Heating Cable on the Roof

The roof and gutter heating cable is secured to the roof via special aluminum roof clips. Warmup recommends using two clips to form the loop that extends over the gutter edge and one clip to form the loop at the top of the triangle pattern.

While this is a great approach, certain field conditions may warrant different approaches. Sometimes you have to “MacGyver it.”

Improvise, Adapt, and Overcome [The MacGyvver Method]

If you were born after 1992, you may not remember MacGyver. There aren’t many action-adventure TV dramas that make it into the dictionary, but MacGyver was not like other shows. It starred Richard Dean Anderson as the eponymous hero who escaped life-threatening situations by avoiding firearms in favor of science, improvised engineering skills, and cobbled-together ingenuity.

While I’m not advocating “cobbling” this installation, I am warning you that there are many different gutters, overhang, fascia trim, and roof configurations and you will need to sometimes improvise and adapt your installation method.

I’ve used several approaches to install roof and gutter heating cable. While there is always a clip at the top of the cable, I have used varied methods to accomplish the lower cable fastening, depending on my situation.

Some variations include:

Installing the Heating Cable In A Gutter

If you have a gutter installed under a roof with heating cable, you must run cable in the gutter as well, or the gutter will become a solid block of ice.

Run the heating cable in and along the gutter bottom. The cable has to be installed under all of the gutter straps. Use care to NOT damage that cable as you pull it through the gutter.

TIP: In order to get the cable under all of the gutter straps, I attach the heating cable to an electrician’s “fish-tape” and feed the wire and cable across the gutter bottom.

Installing the Heating Cable In a Downspout

When installing the heating cable into the gutter downspout, I use the Warmup downspout hanger brackets that keep the cable bend from straining.

This bracket also protects the heating cable from damage caused by the sharp edges. Gutter-to-downspout transitions have sharp edges or exposed screws and you need to ensure that the cable is protected from damage.

TIP: For downspouts that end above the soil line, install the wire to the bottom of the downspout, but no further. Don’t leave the wire exposed outside the downspout or it may become damaged by lawn mowers or grass trimmers.

TIP: When downspouts drain underground to a drywell or are extended in an underground pipe away from the house, try to get the heating cable below the frost line or to the end of the pipe. The frost line in my areas can extend as much as 36-48” deep.

Installing Heating Cable in an “in-line” downspout

Because the heating cable is one continuous wire, you will sometimes have to run the cable down a “mid-line” or “in-line” downspout and then back up in order to continue gutter coverage.

To do this, loop the heating cable down into the downspout. We estimate how much wire we need by holding the wire next to the downspout pipe. We then create a loop that will easily reach the bottom of the drain pipe.

To pull the roof and gutter heating cable through the pipe, we run the electrician’s fish-tape up the downspout and pull the wire down.  The fish tape attaches to the heating wire with electrician’s tape. Once attached, we pull the fish tape down through the downspout and then remove the fish-tape.

TIP:  If we need to add or remove wire slack, we simply pull wire “slack,” down or up, depending on the need.

Power Connection

My electrician handles all of the connections to power and mounting of the controller/sensor.

I always factor in the starting location on my installations so the power wires start or terminate in the same location. I try to pick a spot that is easily accessible for the electrician to be able to get his power to the system.

TIP:  Use only UL Listed weather-proof junction boxes for power connection.

TIP: Visually check all power connections, splices and end seals, and then perform a 2500 VDC meggar check. The meggar check is performed at the power connection end of the cable between buss wire and the grounding braid. The minimum acceptable reading is 20 megohms.

Ending the Cable Run                           

When we have reached our endpoint we cut the excess cable and finish off the cut end with a Warmup NAM-END-KIT. This kit ensures a waterproof, electrically safe end connection.

TIP: If you’re nearing the end, and you think you’re running out of wire, backtrack and widen your triangle bases or reduce the height of the triangles on areas of the roof that are less susceptible to ice dams.

Mounting the Controller

We use the DS-series of automatic controllers, mostly the DS-8C rain/snow sensor controller. Warmup does have an interior mounted controller but we found this system the easiest to use and install.

My electrician mounts the controller near the UL Listed weather-proof junction box. The Warmup Roof & Gutter De-Icing Cable works most effectively with an automatic thermostat and sensing device. The sensor device monitors for moisture and temperature to maintain the required temperature.

Using the DS-8C Rain / Snow Sensor Controller

The DS-8C has a corded interleaved sensor grid that senses freezing rain or snow. The DS-8C precipitation sensor is very sensitive and can detect a single snowflake or raindrop.

The brass cylinder protruding from the bottom of the DS-8C enclosure is the temperature sensor.

TIP: For reliable rain and snow detection, the moisture sensor should be installed in the gutter, facing up, against the fascia board with a 1” “C”-style conduit clamp.

Allow part of the sensor grid to be exposed to snowfall. This allows the sensor to initially trigger when the snow starts falling and remain triggered as long as the roof/gutter heater continues to drip melted snow buildup from the roof edge when temperatures are below freezing.

TIP: For proper temperature detection the DS-8C enclosure must be mounted outdoors, away from furnace vents, dryer vents, and other sources of heat.

Note that, when powered, the DS-8C moisture grid will always remain hot. This is normal. This allows the sensor to continuously melt/evaporate both rain and snow from the grid.

TIP: The sensor has ten feet of cable is pre-terminated to the sensor head. This cable may be shortened on the controller end as required. Do not add additional cable to the interface.

Maintenance of Your WarmUp System

Prior to the winter season, make sure to clean out your gutters and downspouts of leaves and debris.

Warmup recommends checking the insulation resistance of the roof and gutter heating cable sheath with a 2500 VDC meggar. This reading is taken at the power connection end of the cable between a buss wire and the grounding braid. The minimum acceptable reading is 20 megohms.

The wire, controller and sensor installation should be checked every Fall.

The following checks should be done:

Note: Over time, corrosive elements left behind when water is evaporated out of the moisture grid will eventually damage the grid rings. The moisture grid can be easily replaced by ordering and installing a new “Moisture Grid Assembly”.

TIP: To test the system, you can trick the system into starting by wetting the sensor and spraying component cooler onto the grid.

Warmup Roof and Gutter Deicing System


Be Proactive

If you’re unable to rectify the issues that cause your home to have ice dam leaks, then take a proactive step and install a self-regulating cable system that will melt snow and ice and keep a drain path for water to flow freely away from the house, from the roof and gutters.

I consider this roof and gutter heating cable system an investment and cheap insurance.

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