Snow Guards: What Works What Does Not
What to look for when purchasing snow guards.
Snow guards should be made of high-quality materials and have published independent test results to back up their strength. Snow Guard manufacturers should have the knowledge and years of experience to apply these test results to effectively provide the appropriate number of recommended rows necessary to control the snow load on a roof without overloading the snow guards. Snow guards that are incorrectly used may result in premature system failure, property damage, and potential liability for the building owner. Here are a few common errors to avoid:
WHAT DOES NOT WORK!
No Snow Guards On The Building
The absence of snow guards is not an option in this situation. This building was recently constructed, and the contractor did not install snow retention.The business owner may be responsible for personal injury or property damage caused by snow and ice falling from the roof. There is an entryway and a parking lot right underneath where people can park their cans before entering the business. The correct way to install snow guards on this roof would be to address the upper roof first so the snow and ice do not fall onto the lower roof. Snow guards should also be installed on the lower roof to keep the snow and ice from sliding off.
Incorrect Snow Guard Placement
Positioning of snow guards on a roof is an essential aspect of a snow retention system. Snow guards should never be installed on a roof section below the bearing wall, as this can cause ice damming and structural damage. Pad-style and seam-mounted individual snow guards should not be placed in straight lines (As shown in the picture). Snow guards should be in every panel flat, never skip spaces in between the seams as pictured. Many companies will quote an insufficient amount of snow guards for a particular job just to be the lowest bidder. This results in a loss of money from a misapplication because of an insufficient layout that is destined to fail. The snow guards in this image are bending and will flatten out over time, rendering them useless.
Inadequate Snow Retention
One of the leading causes of snow guard failure is a lack of snow retention devices. Multiple rows of snow guards going all the way across and up the roof will assist in balancing the snow load on the roof while avoiding overloading the structure, especially at the eaves. Please refer to our snow guard spacing guideline page for proper snow retention spacing recommendations.
Inferior Snow Guard Designs
A properly designed snow guard has a flat face at the front of the base at least 3 inches wide. Some incorrectly designed snow guards have the attachment point at the top of the base and the face near the back of the snow guard. This creates a leverage point that will pry the base up from the panel over time as constant heavy snow loads consistently push against the rear positioned face. Shown here is a popular restaurant drive-thru that chose a snow guard with a tiny face that is only 1.5 inches wide that features a rear mounted base. As you can see here, the tiny snow guards provide very little protection from sliding snow and ice. A worker had to get up on the roof to manually push the snow off before injury occurred.
Isolating Snow Guards
This is the number one leading cause of failure! If snow guards are only installed above doorways or any other isolated areas, the snow guard attachment may become overloaded and could come off. Snow and ice freeze together, usually across the entire roof. When this occurs, the snow retention system becomes trapped in the frozen mass. When the snow and ice begin to melt, it will not separate easily from the isolated area of snow guards. This can result in an unbalanced snow load placed on the isolated areas of snow guards. The snow retention system will most likely fail in this case.
Miscalculation of Snow Load
People often guess what the snow load is for the project instead of doing the actual research. We base all our snow guard recommendations on the ground snow load rating for the geographical area. The ground snow load is not the actual load applied to the roof structure; rather, it is a measurement derived from historical evaluations and statistical calculations. The ground snow load is used to help calculate a design roof snow load for a specific area and is based on historical measurements taken at various weather stations across the United States. It takes neither the structure's characteristics nor its purpose into account. If you’re not sure what your ground snow load may be, call your local building code enforcement office.
Snow Guard Misconceptions
The placement of snow guards is NOT a mixture of art and science as some manufacturers have claimed. The best spacing guideline is to spread the snow load across the entire roof to keep all the snow and ice from moving initially. Snow rails should NEVER be placed just on the lower half of the roof plane unless it is a short distance from ridge to eave. (See Photo) Never run pad style snow guards in a single line and always use multiple rows going up the roof evenly to spread to balance the load evenly. If this is not done, the initial shifting of the snow and ice on a roof will destroy the snow retention system as shown in this photo.
Some Seam Mounted Snow Guards
Seam-mounted snow guards can be mounted any time of year and are usually quick and easy to install. They do, however, sit up on the high seam which can leave unprotected areas on wider panel flats. This flaw can result in seam damage due to the snow and ice sliding by the snow guards and catching the outer edges as shown in this picture. The final outcome is that the snow guards may get twisted, ruined, and sometimes cause seam damage. Our SnoCleat products address this issue by providing a swivel base that can rotate if the snow guard is subject to impact from sliding snow and ice.
Mid -Face Snow Guards
Mid-Face Snow Guard designs may provide a point of leverage to pry the front of the guard up. The face of a snow guard should always be located at the furthest forward point of the snow guard, creating a leverage point that transfers the load to the lower downhill section of the base. If not, when snow load is applied to the mid-face, it may raise the front of the guard, potentially allowing water to become trapped beneath it. The snow guard attachment can fail if the trapped freezing water expands.
WHAT WORKS
Understand your roof's type in relation to the various styles of metal roofing and their potential attachment limitations. Some roofs are screwed down and can accommodate a mechanically mounted snow retention system, but some property owners may not want to drill any new holes in their roof. In that case, they can use an adhesive-mounted polycarbonate snow guard. A screw-mounted snow retention system is not recommended on most standing seam metal roofs and may void the roof warranty. The most common snow retention options are screw down snow guards and snow rails, seam-mounted clamp-on snow guards and snow rails, or adhesive-mounted polycarbonate snow guards.
Snojax II Installed On A Strip Mall
This is one of the original Snojax II snow guard installations, which were installed on a shopping mall in Camp Hill, Pennsylvania. Notice how the snow guards are correctly staggered across the entire roof. When this project was being built, the building contractor was wise enough to suggest snow guards. This contractor may have saved the building owner from the consequences of having someone injured or paying for property damage to vehicles that frequently park under the roof.
Advantages of Snow Rails
A seam-mounted snow guard has the advantage of being able to be installed at any time of year. If properly designed, seam-mounted snow bars can withstand heavier snow loads. Unlike adhesive mounted snow guards, a clamp-on snow retention system has no release factor so make sure the system is spaced properly by following the manufacturers spacing guidelines. Snow Rails are also available as a screw down version for exposed fastener metal roofs. It is strongly advised to obtain a price quote and layout recommendation before placing an order.
Adhesive Snow Guard Benefits
Adhesive-mounted snow guards have a significant advantage over seam mounted or mechanically fastened guards in terms of long-term roof integrity. If they become overloaded, they will release without causing any damage to the roof panel. When the weather allows, they can simply be reinstalled over the same locations on the roof. Adhesive-mounted snow guards do have a substantial cure time in warmer weather and sometimes require more guards to do the same job as a snow rail.
IceStoppers and Snow Bars
Snow and ice are prevented from sliding under the SnoBar and ColorBar with IceStoppers. They should be mounted perpendicular to the roof panel and have a 90-degree foot on the bottom to keep them from bending under the bar. Our IceStoppers are mechanically attached to the bar with self-drilling tek screws to prevent the IceStoppers from flipping up. IceStoppers are especially important over pedestrian walkways and parking areas. Buyer beware there are some poorly designed snow rail systems on the market that have curved snow stopping clips that simply slide on to a round channel on the bar. Because these clips are not screwed to the bar, they can become windblown and swivel upwards in high winds. This will render them useless to keep snow and ice from sliding under the snow retention system.
Staggered Snow Guard Patterns
The proper way to prevent snow slides on a sloped metal roof is to evenly distribute the snow load. It is necessary to place pad-style snow stops across the entire roof surface, in a staggered pattern. The first pattern should consist of two rows of staggered snow guards at the eave. This image shows how a staggered pattern of snow guards essentially acts as fingers to keep snow and ice in place. Depending on the roof pitch and panel length, patterns of snow guards may need to be equally spaced going up the roof. Always refer to the spacing guideline page for proper spacing.
Multiple Rows of Snow Retention
The recommended number of snow guard rows is usually based on the roof pitch, panel distance from ridge to eave, width of the panel flats and ground snow load rating. Once this information is obtained, a reputable snow guard company will be able to make a proper spacing recommendation. The best way to retain snow and ice on a roof is to have multiple rows of snow retention space evenly, going up the roof, to minimize the chance of movement. If the snow load is not evenly distributed, an avalanche could color, destroying anything in its path, including an insufficient amount of snow retention placed just near the bottom part of the roof. This picture illustrates a properly installed SnoBar system on a large project in Colorado.
Upper Roofs Before Lower Roofs
One of the fastest ways to have your snow retention fail is to allow snow and ice to drop from an upper roof to a lower roof. Snow Guards should always be installed on upper roofs before attempting to mount them on lower roofs. If the snow and ice are allowed to drop from an upper roof onto a lower roof, the force from the impact and additional snow loading will cause premature failure of the snow retention system. This is often overlooked and is a common mistake when installing snow rails and individual guards.
Vent Pipe & Chimney Snow Guards
One of the most frequently asked questions is, "Will snow guards protect chimneys and vent pipes"? The short answer is yes, but only if the snow retention system is installed across the entire roof and not just over a pipe or chimney. This is why we offer three VentSaver models specifically designed for this purpose. A fin on the VentSaver products splits the snow and ice around the pipe. As an added bonus, all VentSaver models include a stainless-steel strap that aids in the support of the vent pipe or chimney. The VentSaver can be used in conjunction with or in place of snow guards for vent pipe and chimney protection.
