This is the first in our series outlining the installation of roof de-icing cable on flat roofs. For the purpose of this discussion, ‘flat’ roofs will include the two primary membrane systems in North America; EPDM (commonly referred to as ‘rubber’) and TPO (Thermoplastic polyolefin). Regardless of slope, Heat Tape PRO self-regulating heat cable is approved for use on all membrane roof systems. The term ‘Flat Roof’ also applies to low-slope roof systems, which typically are less than 3/12, or 14º in slope. We’re proud to say that Radiant Solutions Company offers the most innovative and simple systems for installing heat cable on flat and low-slope roof systems.
Below is an illustration to demonstrate two methods of installing heat tape on a flat roof with valleys. Again, the term ‘valley’ is used loosely because on a flat or low slope roof a valley simply describes the intersection of two roof planes. Valleys on flat and low-slope roofing systems can be so subtle as to be difficult to see from a distance. They can be a gentle swale between two slope where water congregates and moves, hopefully, to a drain location.
Heat Cable System Parts: Our Hardwire Connection Kit (Point 1) which is often used on flat roof applications to connect the heat cable into a junction box (either 120 volt or 240 volt). Anyone with basic mechanical skills can make these connections. (Point 2) A Jumbo Single Cradle Glue-Down Clip (DDK-719-1) can be used to secure heat cable to just about any surface, including rubber and TPO membranes. (Point 3) SB 190 is the adhesive of choice for all of our glue-down heat cable clips. (Point 4) Keep heat cable near the low point of the valley to encourage water to drain off the roof. A Jumbo Double Cradle Glue-Down Clip (DDK-719-2) (Point 5) is used for double heat cable runs. These clips are also commonly used to install double heat cable runs inside commercial open-face downspouts.
One Cable or Two? We are often asked if a low-slope roof with a valley should get one cable or two. Generally speaking one run of Heat Tape PRO will provide adequate de-icing in a valley. That said, if the roof has severe ice build up or if it intersects with other features such as roof-top equipment, having a second melted pathway through the snow and ice may be advised.
A couple considerations when installing heat cable around scupper drains… First, it’s easy to slap an additional DDK-2 Heat Tape Clip (Point 6) down to provide another loop of cable as shown. Next, consider using some RSC-555 Cable Separators to keep things tidy (Point 7). Heat cable separator clips are cheap and easy to install. The below illustration also shows an up close view of both a single run and double run of heat cable on a low-slope membrane surface. Also, strangely, a dog creeping in on the right.
As we frequently say, when it comes to managing snow and ice on flat roofs you should follow the ‘think like water’ principle. Put simply, this means that when determining your heat tape layout you should observe how water appears to be moving around on the roof. An easy way of seeing this is to look for where dirt and debris on the roof surface is collecting. These areas represent low spots that should possibly be factored in to your design. The goal of the cable system of course being to create pathways for water to use to escape off the roof. Normally, the water needs to move to either a perimeter drain, often called a scupper, or to an interior field drain. Those topics are covered on this page.
Apply a generous amount of SB 190 adhesive to the back of the roof clips and smoosh the clip down onto the roof surface. Easy.
Prep work is essential. Always clean the surface before applying clips. Use a cotton rag and rubbing alcohol and clean an area slightly larger than the clip being installed.
The RSC-555 cable separator clips is used to keep cables spaced consistently, which helps create a professional look and a super efficient melting pattern.
Here is a DDK-719-2 Jumbo Double Cradle Glue-Down Roof Clip on a TPO membrane roof.
