Snow guards are plastic or metal devices that are designed to slow or stop the advance of ice and snow from sliding off of metal roofing all at once causing damage to structures, landscaping, vehicles and people.
Snow builds up on your roof during winter storms, as the melting starts from the bottom, it creates a moveable wall of ice and snow that will slide down your metal roof and damage whatever is below it.
According to the National Roofing Contractors Association, areas with significant snow should only use the snow retention guards above entrances. This is because the guards may cause too much snow to accumulate, which can damage the roof.
Here in North Texas, no one would expect to get 12 inches of snow, but that's what we got in December 2010. Metal roofs are very popular here in Texas, unfortunately after the snow melted, many people found there gutters had been damaged or destroyed from snow sliding off their roofs in large sheets.
Types of Snow Guard
The most efficient design for the pad style guards are those with a 3 inch to 5 inch wide forward mounted flat face with solid support struts and base. The guard should be 100 percent prime virgin grade polycarbonate that is UV stabilized. A waffled base multiplies the bonding power of a smooth bottom snow guard.
Clear polycarbonate is virtually invisible and will not create corrosive galvanic reactions caused when dissimilar metals are exposed to moisture.
The layout of the guards on the roof is the most important part of the entire system. For the best system, use the correctly designed guards and install using a professional layout.
Many companies quote far too few guards in order to be the lowest bidder for the job. The result is an inferior layout destined for failure.
There are a few reputable snow guard manufacturers such as snoblox that have on-line programs that will help you determine how many guards should be used on a particular project.
A reliable layout will have multiple staggered rows of guards, with each guard mounted in the center of the panel where the snow and ice actually moves.
The most common layout mistake is to only install one row down by the lower edge of the roof. This layout gives the snow too much room to build up velocity and cause damage to the guards. It also allows for too much load on the lower roof section, causing an unbalanced structural load.
A properly designed layout will equally distribute the snow load across the entire roof, minimize the snow movement velocity with multiple rows and break up large snow fields by staggered guard placement.
The first row of guards should be positioned approximately six inches from the edge of the roof and the second row is approximately twelve inches from the edge.
Two rows of guards is usually enough for a pitch of 1/12 to 5/12. For 6/12 pitch and up, an additional row should be installed. On runs of 18 feet or more, it is recommended to add a row of guards halfway up the run.
Snow retention devices can be installed with adhesive or mechanically fastened with self-drilling screws. While mechanically fastened snow guards will support more weight than glued down, the roof panel must be penetrated.
To install the roof panel guard with adhesive, wipe the back of the guards with denatured alcohol, then wipe down the area on the roof where the guard is to be installed. Apply a liberal amount of adhesive on the back of the guard. I suggest using SB-190 Adhesive found at any roofing supply house. Push it firmly to the cleaned area on roof. Use enough adhesive so it squishes out the side. Be sure to follow manufacturer's suggestion on back of adhesive.
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