Snow Retention Devices

 

snow retentionThe design of snow retention devices originated in the colder European countries and has been in use for hundreds of years. The indigenous hardy people who took up residence in the Alps and in the Northern regions of Scandinavia learned early on the benefits of controlling the accumulation of snow on their roofs. These retention devices crude by today’s standards utilized stones and logs to increase the friction between snow and the roof to retain the snow on the rooftops. The desired results of the retention devices were to maintain the snow, prior to insulation; this would provided an insulator and helped keep the structure warmer. These pioneers in snow controlled devices did not stop at their dwellings but continue today to control all types of snow accumulation. The regions hillsides are still today peppered with snow retention devices to prevent snow from sliding over roads and mountain passes.

 

A snow retention device is a guard or system that when properly installed to the correct specifications of the roof will evacuate the snow accumulated in a predictable and controlled fashion. The snow is evaporated and thawed in a controlled predictable timeframe rather than a sudden and dangerous rooftop avalanche.

 

Why are Snow Retention Devices Necessary?

  • To Protect your Customer or Residents. Signage warning the individual of pending possible dire circumstances from falling snow or ice does little to lessen your liability. When snow slides and falls, it can be extremely dangerous and costly and pose a very serious threat.
  • To Protect Private Property (Vehicles). Sudden snow falling from a steel roof can total a parked car beneath leaving the owner of the building with a costly insurance ordeal.
  • To Protect Buildings and Roof Elements. Gutters, flues, vents are all accessible to damage from moving snow. Building walls and foundation are not immune to the effects of improper snow retention as well. Metal walls can be quite fragile and in some cases can implode due to snow sliding.

 

With the winter months giving way to what we in the North call spring, the time to reevaluate the necessity of installing snow retention devices. The cost associated with procuring and installing these devices can be substantially lower than the damage caused by a normal winter’s snow accumulation. Liability insurance premiums and litigation associated with roof snow can all be reduced with a proper system installed. The science to mathematically calculate the proper snow guard for your typical roof can assure against product failure and proper snow retention.

 

snow retention

The vertical weight of the snow on the roof translates into the “drag load”. The snow retention system in place must resist this calculated drag load or they will be torn away from their mountings. Once this drag load or vector force is calculated then it is possible to design and install a snow retention system that will work for your roof and its slope.

 

The following chart calculates the load that a snow retention guard must resist. The vertical load is always the design roof’s snow load. In this example we will assume a 35lb / Sq. Ft. The load the guard must resist is the angular or vector force exerted by the snow. Solving for vector multiple the vertical, 35psf x Sine (.382) = 13.37 psf. To get the units in pounds per panel we extend that figure by the length of the roof. The result of this roof shows a snow guard that must resist 978 pounds of force being exerted on it by the snow.

 

Jottan-Jorel offers a variety of commercial roofing solutions for your new or existing roofing needs. Jottan-Jorel specializes in preventive maintenance, emergency repair and service along with new and reroofing services.

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