![]() ![]() (470 lb) has been chosen, four rows of these parts per seam will be needed to withstand the angular force (125/461=3.68, or ‘4’).Ģ. If angular force equals 461 kg (1016 lb), and a cleat snow guard device with the tested allowable load of 125 kg For example: Figure 6: Roof valleys are very susceptible to damage by uncontrolled sliding snow.ġ. ![]() ![]() To determine the number of snow guard rows needed, the tested allowable load of the snow guard being considered should be divided into the angular force sum. Once the angular force is calculated, snow guards can be chosen by consulting the published test data from the manufacturers. (There are several commercially available calculators on the Internet that can walk through this process and complete the calculation.) Multiply the sum of Step 3 by the seam-to-seam width measurement of the roof. Multiply the sum of Step 2 by the eave-to-ridge measurement of the roof.Ĥ. Multiply the roof snow load by the sine of the roof angle.ģ. In the case of a metal roof, the force snow guards can withstand can be calculated simply by following these steps (Figure 7): Figure 5: Gutters, facia, and trim can all fall prey to an uncontrolled avalanche of sliding snow and must be protected by snow guards.Ģ. You May Also Like Standards for specifications: MasterFormat, SectionFormat, PageFormat, and you Simply stated, the calculation takes the vertical weight of the snow and reduces it by the sine of the roof angle to arrive at the angular force exerted on the snow guard. The forces of snow on a rooftop should be mathematically calculated to ensure product success. A small investment in snow guards can protect a building owner from extensive repairs and long-term maintenance headaches. Ice and snow sliding uncontrollably down a roof valley can open up seams and destroy valley flashing (Figure 6). Gutters, fascia, trim, signage, light fixtures, antennae-anything attached to a roof-can fall prey to an avalanche of sliding ice and snow (Figure 5). Extensive rooftop damage can be caused in an instant. While it is clearly important to protect people and equipment, it is also important to defend the building itself from avalanching snow. Figure 4: Snow sliding uncontrollably from roofs can be thousands of kilograms, and can cause devastating effects on objects below. The volume of ice and snow quickly exiting a roof can be measured in tonnes and can cause significant damage. Vehicles, mechanical equipment, and landscaping can also be in the path of rooftop avalanches (Figure 4). Often, it is not just people at risk from the ravages of falling ice and snow. The goal is a well-managed snow pack, maintained on the roof by snow guards, where it can be naturally melted and eliminated (Figure 3). The addition of snow guards is a simple ‘insurance policy’ to protect the designer, owner, and public from falling snow and ice. If someone were to be hurt by falling snow it may be an invitation for a lawsuit. It might actually create a greater issue for the building owner because the sign admits to a problem with falling snow and the owner is not taking proper remedial action to protect the public. Figure 3: Snow guards retain snow on rooftops so it can be managed and predictively removed by sublimation and thaw.Īdding a sign to the building warning pedestrians of falling ice and snow is not an acceptable alternative to snow management. ![]()
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