Metal Roof Snow Guards – For gutter installers interested in adding snow guards to their product offerings, the first step is to understand how they work and how to choose among the many guards on the market.
Snow guards are roof-mounted at spaced intervals and in two or more rows near the edge of a roof. The idea is that, as snow and ice back up against the guards, it will harden and create a dam. In turn, the ice dam will prevent the mass of snow from sloughing off the roof all at once in a single avalanche.
While all agree how snow guards are supposed to work, how can gutter installers choose among the many different designs? “First, the face of the snow guard has got to be big enough to hold the snow,” advises McMullen. Minimum size, he suggests, is 2.25 inches high and 3 inches across. Second, he favors a flat face rather than a pointed design, since he believes the latter is more decorative than functional and does not hold back snow.
“The height and shape of the face of a snow guard determines its ability to hold back layers of ice and snow,” continues McMullen. “Snow guards need to be mounted in the lowest portion of a roofing panel where the snow and ice actually moves. The flat surface should stand at least the height of the seam, creating a connected field to hold snow and ice stationary until it can melt off safely.”
Snow guards not only come in different heights and with different faces. In addition, the face may stand up from the edge of the mounting base or from the middle, so the guard looks either like a letter “L” or an upside down “T.” Further, the L-shaped products can be designed so that the perpendicular face which holds back the snow is on either the forward or rear edge of the mounting base.
No Snow BlocksIn other words, snow guards can be made so that snow and ice must either: pass over the surface of the mounting base before being halted by the perpendicular face; pass halfway over the mounting base; or encounter the perpendicular face first, so that snow and ice do not pass over the mounting base at all. McMullen endorses the latter design since, as he advises, “that means the weight of the snow pressing against the face will push the base even more securely onto the surface of the roof.” With the other designs, he believes, the weight of the snow against the face of the guard can cause the mounting base to pull away from the roof surface.
“The correct spacing and number of the snow guards is also important for the system to work properly,” McMullen relates. Manufacturers should provide tested spacing layouts based on the roof pitch, panel runs from the ridge to the eave, panel widths and profile, and the snow load for which the home is designed. Using these layouts as templates, installers can take a tape measure and easily mark out where snow guards should be mounted.Snow Curl
Snow guards can be mounted to the roof surface either with mechanical fasteners, adhesives, or tape. For his part, McMullen recommends that only adhesive mounting be used on floating-type standing seam metal roofs. “This doesn’t restrict normal thermal expansion and contraction of floating metal roof panels,” he points out, “and provides a release feature that prevents panel damage, and eliminates potential impairment to the seams.” In addition, he cautions installers against tape fasteners as anything but a very temporary solution.
Finally, gutter installers have a choice of materials for snow guards. Metal guards are available in colors that match roofing panels. However, McMullen suggests the aesthetic advantage of color-matching can be offset by the “sundial effect” of upright metal snow guards casting shadows on the roof. Metal guards can also become brittle in cold weather, he adds, and sometimes can produce rust-causing galvanic reactions with the metal roof.
The other choice of material is clear plastic, including polycarbonates that are stabilized against ultraviolet rays to inhibit yellowing and cracking. The material does not cause galvanic reactions and, because it is clear, does not cast shadows.
On the other hand, home-owners and architects can color-match the plastic snow guards to their roofs, yet color-matched guards and roof panels can fade differently over time “if the snow guard is not the same material as the roof, or was painted at the same time with the same type of paint,” responds McMullen.
He cautions further against the idea of installing snow guards only above, say, the front entranceway of a home.
“That’s a misapplication,” McMullen warns. “Snow guards only hold what’s above them and not what’s beside them. If you try to segregate the snow on a roof and only hold back the snow above a doorway, then that will put stress on the snow guards and might cause them to pull off. The imbalanced loading is detrimental to snow retention.”