Top tips for snow retention on metal roofs

As the popularity of metal roofing grows, so do the options for preventing dangerous and damaging avalanches of ice and snow. While you may think that anything made to stop it, should stop it, there is a lot of science that goes into a properly engineered snow retention devise. Mother Nature is not easy to predict, but good science leads to more effective products.

Keith Lipps, Vice President of Metal Roof Innovations, Ltd., (S-5!), is an expert on the topic, and notes: “Snow retention is some simple science mingled with a touch of art-in-practice.

“The science is not difficult to understand, and not too debatable.

“The art-in-practice is discretionary, opinionated, partly supported by science, partly by myth and hotly debated amongst users and purveyors of such product offerings.

“Snow effects, coupled with accompanying winds are difficult to predict and the architecture and density of a snowbank is varied at any given time. These unknown variables lend to the controversy.”

With that in mind, here are a few simple tips for selecting and installing successful snow retention.

Use only warrantied systems
There is consensus among our sources that buying from a manufacturer who warranties its products is critical. According to Snobar, it’s by far the most important tip for contractors/designers/architects. “Always buy from a snow retention manufacturer that will back it up with a warranty and inquire if they have product liability for their snow retention systems,” said Jason Nagaki. “If they do, it most likely means they’ve been in business for years and have good knowledge about the industry.

“What I consider bad competition are the guys that make up their own snow retention system and sell it to the owners or owners’ reps not knowing what all goes into a design for a proper snow retention layout on a roof. The building owner doesn’t get a warrantied system from these kinds of installs.”

S-5! agrees and warns: “There are plenty of snow retention systems on the market that are willing to sell you an untested system, use these systems at your own risk. An untested system is one that has not been tested on how it will perform overall or how it will preform on specific roofs.”

Buy only well-engineered and tested systems
This tip really goes hand-in-hand with Tip #1. S-5! noted that reputable manufacturers will freely share information to assure a properly designed plan. “Testing specific to roofs is essential to running any type of engineering calculations for a designed and engineered snow retention system. If you’re installing on “Manufacturer X” roof, make sure you know how the system should perform on “Manufacturer X” roof. Responsible snow retention manufacturers can share with you their testing on each roof that their system works on. If not, don’t use it.”

Seek design advice
When in doubt, architects and designers should not hesitate to seek advice from the manufacturer during the design phase. “They should call a snow retention manufacturer so they can draw a properly designed snow retention system on their roof,” Snobar’s Nagaki said. “Worst case scenario, the architect/designer should put a note on the roof plan where they want snow retention and in the specs that the contractor must have a properly designed layout from the snow retention manufacturer. I can’t count how many times where the contractor tells us that the architect/designer just has one row of snow retention drawn on the roof plan, so that’s all they order, and 9 out of 10 times the project is under designed and the owner doesn’t even realize it.”

Alpine SnowGuards echoes the advice. “The biggest (and ultimately most costly) mistake we see time and time again is not getting a recommended layout prior to bidding, purchasing, and installing them. If you don’t install the proper quantity of snow guards and/or brackets, in a recommended layout pattern, you run the risk of system failure.”

Remember: logical isn’t always practical
While it may seem logical to place a snow management system only above doors and other isolated areas where you are most concerned about avalanching snow, Alpine SnowGuards warns that you may be missing key fault areas. The company offers: “Snow and ice tends to build up and away from any roof obstruction (in this case, a snow guard) at a 45 degree angle. This means that a snow guard installed above a doorway in the middle of a 100 foot long eave area on a building with a 50 foot rafter length would carry the weight AND mass of more than half of the entire roof.”

Don’t ignore directions
It comes up time and time again: follow directions! “You’re taking the time to find the best snow management system available for your project, so installing the system correctly is crucial to ensure that the system functions to its full potential,” offers Alpine SnowGuards. “Some common mistakes we’ve seen run the gamut from not tightening set screws or fasteners to the proper torque settings, to not flashing properly in order to comply with roofing industry best practices.”

And make sure you understand what you read, S-5! reminds installers. “Make sure you understand the manufacturers installation directions and how this is critical to the designed performance of ANY snow retention system. Responsible manufacturers go to great lengths to create installation instructions that, if followed, get the best results of their system.”

This photo shows a failure of a bar system in Colorado. Notice that three rows of bar are concentrated close to the eave. Snow retention should be equally spaced up the roof area to control the dynamic loads of sliding snow and ice. Two-thirds of the snow load on this roof was being held by just the upper bar. The lower two bars only held one third of the snow. In addition, this system failed because it used isolated placement and extended the bars too far across the panel at the end of the run. These clamps were also installed over batten strips, which is not a good idea.  SnoBlox-Snojax notes that this failure could have been avoided by equally spacing the rows up the roof, by extending the runs the entire length of the roof, and by using clamps that would have attached under the batten strip, not on it.

This photo shows a failure of a bar system in Colorado. Notice that three rows of bar are concentrated close to the eave. Snow retention should be equally spaced up the roof area to control the dynamic loads of sliding snow and ice. was being held by just the upper bar. The lower two bars only held one third of the snow. In addition, this system failed because it used isolated placement and extended the bars too far across the panel at the end of the run. These clamps were also installed over batten strips, which is not a good idea. SnoBlox-Snojax notes that this failure could have been avoided by equally spacing the rows up the roof, by extending the runs the entire length of the roof, and by using clamps that would have attached under the batten strip, not on it. SnoBlox-Snojax photo

Special note for standing seam: connections, connections, connections
Snobar adds this tip about installation of snow retention systems on metal roofing. “If your snow retention system is being attached to a standing seam metal roof by clamping it to the seams, the contractors needs to make sure that there are enough fix fastened points in the panels so that the panels don’t slide from the weight of the snow, that the snow retention is going to hold. Just having the roof clips that holds on the metal panels is by no means enough to keep the panels from sliding.”

BONUS Tip: Download this MCA document
Want a good, unbiased explanation of snow retention selection and installation? This suggestion comes from Keith Lipps, S-5!: Go to the MCA website (metalconstruction.org) and under the Technical Resources tab, download the document “Metal Roof Design for Cold Climates,” or DOWNLOAD HERE. The document contains some illustrated technical description of the science behind snow retention along with an explanation that makes it easy for any designer or contractor to select and apply a product adequately to prevent failure and catastrophe.

F In this picture, there are two roof areas that are side by side. On the lower roof you will notice four rows of snow retention. It was designed this way because the manufacturer took into consideration blowing and drifting snow from the upper roof area.

In this picture, there are two roof areas that are side by side. On the lower roof you will notice four rows of snow retention. It was designed this way because the manufacturer took into consideration blowing and drifting snow from the upper roof area. – Snobar photo

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