Roof Snow Fences FAQ

A snow fence is a horizontal structure usually attached near the eave that creates a barrier to snow and ice movement. Snow above the snow fence will settle against the snow fence over time. Snow fences are recommended on eaves where even small amounts of snow and ice falling would be problematic. Roofs over high traffic doors and garage entrances and roofs that drop snow onto walkways around commercial buildings are examples. Ice flags and Ice screens are recommended to hold even the smallest amount of ice and snow from falling off the roof.

The number of snow fences and the placement of the brackets is determined using ASCE standard calculations. Rocky Mountain Snow Guards can determine the placement and number of snow fences quickly and easily to fit your specific situation.

This is generally a bad idea. Snow and ice will stay in place above a snow guard at roughly a 30-45 degree angle. This is known as the angle of repose. Because snow isn’t held in a straight line up the roof from the snow guard there is extra load placed on snow guards at the end of the pattern. Those snow guards may become over-loaded and fail. The same theory applies to snow fences where the end bracket may be over loaded and fail. Snow guards and snow fences should installed to control the snow on the entire roof area.

The number and placement of snow guards necessary varies greatly based on a variety of factors including location of roof, roof slope, roofing material, etc. Rocky Mountain Snow Guards can recommend the correct number and placement of snow guards according to your specific situation. Generally, the minimum recommended number of snow guards is 3 rows starting at the eave with snow guards placed 24” apart within rows. The center row is offset 12” to create a zig-zag pattern. Additional snow guards may be necessary above the minimum 3 row pattern. Rocky Mountain Snow Guards can easily determine the appropriate quantity and pattern for your specific situation.

Our snow guards and snow fences are designed to hold static snow and ice loads. Moving snow is a dynamic load that cannot be calculated. If you have a two story house and the snow drops off the second level and onto first level, and then onto the driveway, you may want to consider a combination of our snow guards and snow fences. Our design and layout services will help you determine the best system for your particular roof.