The Importance of Snow Retention Layout

Education is key when installing a well-designed layout to prevent failure

A snow retention system is an important factor in preventing damage to metal roofs from the buildup of ice and snow.

Today’s most popular metal roofs are manufactured to be self-cleaning, but the low friction surface creates a problem in areas of the country that get snow. A layer of water forms between the roof panel and the snow, making the snow release and slide down the roof when the metal roof warms. Huge liability claims have been made against building and business owners as a result of the damage caused by the sliding snow and ice.

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Photo courtesy of S-5!

That’s why all metal roofs on buildings and homes in areas that get snow should have a well designed snow retention system to protect against sliding. In order for the snow retention system to work properly, the layout is crucial. Although it is an upfront expense that contractors and building owners might not want to consider, it is imperative to prevent damage and resulting costs down the road.

Snow Guard Systems
A properly installed snow guard system is one of the most important safety considerations of having a metal roof. Without one, snow can damage property in ways that one may not even think of—crushing windows, damaging HVAC systems, breaking gutters, ruining landscaping and allowing water buildup against a buildings’ foundation that causes flooding.

“When the snow guards failed, which they often did, the retorts from the purveyors were always the same: ‘You didn’t use enough of them, or you must have put them on wrong,’ said Rob Haddock, inventor and founder of S-5! attachment technology. “But no company offered any solid, scientific advice on how many are enough?”

In 1992, S-5! changed that, de-bunking the myths and mystery with what it believes is “the right way,” involving some simple math and science.
“Even still, the most common mistake is the failure to design the frequency of snow retention devices to the actual sliding or gravity loads to which they will be exposed in service,” said Haddock of Colorado Springs, Colo. “These factors vary on a site-specific basis. It is imperative that job-by-job, the correct data is considered.”

S-5! considers the following:
1. The design roof snow load in pounds per square foot (not ground snow).
2. The sine of the roof angle.
3. The tributary load area.
4. The allowable load for the snow guard (determined by applying a reasonable factor of safety to appropriately tested and documented ultimate failure loads for the device).

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Photo courtesy of Sno Gem.

With the above information, the rest is really only a matter of math and common sense, Haddock said. Multiply No. 1 by No. 2 by No. 3 and divide by No. 4 to arrive at frequency of devices per panel.

Failure to perform the necessary math results with either over-design or under-design, Haddock said. Under-design causes system failures and roof damage, also endangering life and safety. Over-design causes unnecessary expense.

“Doing it the right way by performing the necessary calculations also enables users to accurately compare apples-to-oranges when evaluating snow retention costs and performance,” he said.

There are two main types of modern snow retention for metal roofs: pad style guards, which are used to create “field-type” layouts, and bar systems, which are used to create “fence-type” layouts. The main purpose for both is to hold the snow in place and allow it to safely melt and gradually come off of the metal roof. Both have their benefits.

Pad Style Snow Guards
When using pad style snow guards, the concept is to use multiple staggered rows of guards, which are mounted into the roof panel and they work together to protect against snow slides.

Pad style guards are usually made from UV stabilized polycarbonate, cast metal or stainless steel. Other metals used include aluminum, bronze, copper and steel.
The staggered pattern holds the snow and ice in place, preventing slides. Placed in multiple rows, the pad style snow guards create a field, not a straight line, that forms a fence.

Roofs are designed to hold the snow load, but not when the loads are uneven and are bigger at the eaves. When used in a field pattern, they are very effective at holding snow and ice.

Polycarbonate guards are typically glued onto the roof to avoid additional holes in metal panels. Peel-and-stick options are also available for cold weather installation and have a pointed guard designed to break the snow and ice. Screw mounted guards can also be used using non-corrosive screws with neoprene washers and a high quality silicone sealant.

Bar Style Snow Guards
Another snow guard system is the use of the bar style snow guard, a bar mounted perpendicular to the panels. There are many types of bars, some with multiple bars and high fences. Bar systems can be found in aluminum and mill finish or they can be custom powder coated to match the roof panels.

Bar systems use ice stoppers between the seams to protect the roof from snow and ice that can slide under the bar, creating a “fence” layout. The ice stoppers are mounted perpendicular to the roof panels to prevent snow and ice from going over the bar. They should be mechanically fastened to the bar securely with a foot, to prevent being flipped over or under the bar. The ice stoppers can also help prevent the panel from lifting during high winds.

Layout For Both Systems are Key
Regardless of which snow retention system you choose, almost all failures of snow retention are due to incorrect installation or layout.

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Photo courtesy of Snobar.

Today’s systems’ No. 1 priority should be to hold the snow and ice in place with multiple rows up the roof, so the snow and ice can gradually melt or come off the roof in smaller quantities. A misconception is that these systems are trying to stop the snow from sliding entirely and are holding the snow in place—which can cause extensive damage to the roof structure and even result in collapse due to the heavy weight.

According to studies done by both the Army Corps of Engineers and the American Society of Civil Engineers, layouts should be based on the following design considerations:
• Rows should be spaced uniformly. Multiple rows of reasonably strong snow guards are preferred over one very strong last line of defense placed near the eaves.
• Multiple rows of snow guards spaced well apart up the roof are better at holding snow in place (i.e., avoiding the large dynamic loads created by sliding snow) than one row of last-resort snow guards placed near the eaves.
• A short snow guard on a long roof without other snow guards must be able to resist all the snow located within outward 45-degree angles up a slope of its location. The loads at the ends of such a snow guard are about twice the average load on it.

Mistakes Commonly Made
Only placing snow retention devices near the eaves of the roof is a common problem. Also, just protecting isolated areas is also an ineffective solution. This usually occurs when buildings are constructed without a proper snow retention layout integrated within the design.

“The biggest mistake when installing a snow fence layout is trying to get the architect to get an accurate layout,” said Jason Nagaki of Snobar, Denver, Colo.
“Usually the architect’s drawings will not include what the building will ultimately need for snow retention. What would be great is if they would work with a manufacturer from the beginning so they could get a more accurate drawing and it would include what it would need.”

Typically the contractor working on the project will see the architect’s drawings and then add some bars or guards in isolated areas such as where air vent stacks are located, doors and entryways.

“This is a recipe for disaster,” Nagaki said. “The key is to work with an architect and then have the owner bring the plans to a reputable manufacturer to get a proper layout.”

Snobar provides in-house shop drawings of proper snow retention layouts after they see an architect’s plans.

“In a perfect scenario, we would work with an architect from the beginning and have an adequate snow retention layout within the final drawings, which will be presented to the contractor before the building is constructed,” Nagaki said.
To help customers design the right snow retention system, S-5! offers an online calculator.

“The ColorGard Calculator ensures that you identify the correct materials for your project,” Haddock said. “It also allows you to save your projects online for later use. Based upon your input the calculator will indicate the appropriate number of rows of snow retention to install, and a total parts list needed.”

In addition, many of S-5! distributors will gladly provide free layout services of any S-5! snow retention system.

Education is Key
Contractors need to educate themselves about correct snow retention.
SnoBlox-Snojax, Lemoyne, Pa., offers a class for snow retention at www.snowretention101.com, where you can get a brief overview of the different kinds of products and the benefits.

“The biggest problem we see with installation layout is that people need to be more educated on it,” said Howie Scarboro of SnoBlox-Snojax. “The No. 1 reason why snow retention fails is due to the failure of the layout. The most common mistake we see that people make is that they put only one or two rows on the metal roof, when multiple rows are needed. The public in general is very uneducated about it.”

Snoblox-Snojax also offers www.snowguardspacingtool.com, where if followed correctly, can help you space their equipment.
For example, a user will enter precise project details in six steps, and then receive a price quote and layout for a project.

A Lot of Research Goes Into Layouts
Many considerations go into getting a proper layout. Whether you plug numbers into software, or go directly to a reputable manufacturer, as long as you get a correct plan, your roof should be protected.

Sno Gem, McHenry, Ill., looks into many considerations when planning a layout.
“A significant factor in the success of any snow retention product is the importance of getting a correctly engineered layout,” said Jim Carpenter with Sno Gem. “Although a worthwhile investment, if an owner does not want to pay for a stamped and engineered layout, our office can provide a recommended layout upon request.” A recommended layout is not a general layout, Carpenter said.

“When requested, we look at the particular geographic characteristics of where the product is being installed. In addition, the layouts are also largely determined by what products are being used,” Carpenter said. “There’s not just one kind of metal roof. There are so many different roof systems and the layout may vary depending on what roof system is being used.”

Contractors must make sure that the snow guard design is a match for the project panel. Individual pad style guards should fit in the center of the panel. For bar systems, make sure that the clamps used are a correct fit for the panels.

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Photo courtesy of SnoBlox-Snojax.

“We look at everything, including surrounding area snowdrifts, historical snow accumulation and, of course, the building’s characteristics, like roof panel manufacturer and roof slopes,” Carpenter said. “This is all critical information to determine an appropriate snow retention layout and what works in one area, may altogether not work in another.”

As more and more roofing companies offer metal as an option, many are also developing their own snow retention systems. “Be careful of contractors simply bending metal and fastening it to a roof to substitute for an engineered snow retention system by a company with a proven history of providing quality snow retention systems,” said Carpenter.

“Sno Gem is solely in the snow retention business. All of our products are designed, engineered and tested. We have a proven track record over 20 years in the industry. Snow retention is what we are in business for.”

Warranties
A properly installed snow retention system usually has a lifetime warranty. However, keep in mind that these warranties are only effective if they are installed correctly, using a layout that is recommended by the manufacturer.

If you install a poorly designed system and it fails, causing damage, the burden will fall on the contractor or possibly the homeowner. If a homeowner decides to implement an inadequate system to save money, the homeowner will be responsible for any damage that occurs.

S-5! offers a Certified Engineer Stamp Program for its snow retention systems.
“The S-5! Certified Calculation Program allows installers of ColorGard to submit their ColorGard snow retention system project calculations to a registered professional engineer for review,” Haddock said.

“The engineer will review the calculations and, if approved, affix his stamp of the appropriate state providing increased assurance that the S-5! ColorGard snow retention system will last as long as the roof itself. It is a very simple online process.” Snow retention manufacturers like S-5! stand behind their products, by offering a warranty with written assurance of comprehensive coverage and system performance, not just empty sales claims, Haddock said. Manufacturers should be able to provide a lifetime warranty on systems that measures up to the task—not just for a few years, but for the life of the roof.

According to Haddock, a good snow retention warranty should provide:
•  That the attachment clamps or device will not pull off the seam, break or otherwise cause the system to release
• The system crossmember and its anchorage will not buckle, break or otherwise fail under load
• The system will not corrode or cause corrosion of the roof
• The snow retention system will not damage the roof
• The system will color-match the roof for the life of the roof.

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