Snow Guards 101

Snow guards help stop the movement of a snow avalanche from sliding off the roof all at one time, preventing damage to property, landscaping and people.

By Tim Gentry, Vice President of Technical Services, DaVinci Roofscapes.

As a roofer, you may not be as familiar with composite roofing as you'd like to be... especially when it comes to understanding how the product performs in winter weather conditions. We're here to help.

These are some of the top questions we get at DaVinci Roofscapes about snow, snow slides and guards.

Q: Does snow slide off of a composite shake or slate roof?

A: Snow tends to slide off all roofs, but is more likely to slide off metal, natural slate, glazed tile, and composite tiles. This is due to some of the same physical characteristics that help to make synthetic roofs so long lasting and beautiful.  At DaVinci, our roofing products have smooth surfaces and don’t absorb water. This means that snow and ice have no place to “grip” as it might with some other roofing products. When snow begins to melt from a warm attic underneath, the snow blanket on top may slide off the roof all at once. Sometimes this is an "avalanche" effect, which can be dangerous to people standing underneath and to valued landscaping. 

Q: What is the solution?

A: Installing a pattern of snow guards or attaching snow fences near the eave can reduce or eliminate snow slides. Guards work by adding friction to the roof. Snow fences on the other hand, create a barrier to prevent snow movement.  Snow guards are the preferred product for most areas while snow fences are used in very high snow areas like ski resorts.

Q: Who should consider snow guards?

A: Snow guards should be considered in parts of the country where accumulating snowfalls occur. Many roofs or parts of roofs may not need any snow guards at all. In fact, some structures are designed so that snow will slide off of the roof, reducing the stress on the structure.

Q: How do I know if the house I'm re-roofing needs snow retention?

A: It all depends on what the snow may fall on as it slides off of the roof. If you're installing composite roofing in a geographic area where there is regular snowfall, then snow guards should be strongly recommended to the homeowners. The placement of snow guards should be considered on roof areas where sliding snow might land on people or property. Decks, doorways, walkways and driveways are obvious examples of such areas.

Q: What snow guards should I use?

A: There are many different types of snow guards. Snow guards for use on DaVinci roofs must have an attachment strap and be manufactured of long lasting- non-corrosive metals. The best types to use with composite roofing products are manufactured of copper, stainless steel or coated aluminum. Plastic snow guards, typically used on metal roofs, are not recommended for composite roofs.

Q: I installed a composite roof last summer without snow guards. The homeowners had bad winter experiences with snow sliding off the roof. Can I go back in and retrofit snow guards on composite roofs?

A: Yes. While the best time to install snow guards is when a composite roof is being installed, they can be retrofitted. There are snow guards available that are specifically designed to be installed after a roof has been installed. These are known as retro-fit snow guards and this type of snow guard won’t compromise the integrity, warranty or longevity of a composite roof.

Q: What is the actual process of determining where snow guards should be placed on a roof?

A: Great question .. and I'm leaning on an expert to answer the question. Lars Walberg is president of Rocky Mountain Snow Guards.

Here are the steps he's recommending:

"First we look at a roof diagram for the building, either an aerial picture of an existing structure or architectural drawings of a new structure," says Walberg. "We ask the roofer or homeowner to identify areas over driveways, walks, dog runs, decks and other key 'traffic' locations. Then we design a snow guard system to help protect those eaves and areas from snow slides."

According to Walberg, the science behind the operation comes in determining how many guards to specify, at which locations and to determine the snow load and retention.

"We've calculated and designed a number of different patterns of snow guards that are effective for different situations," says Walberg, "Steeper roofs, longer runs and the lower coefficient of friction of the roof covering all play a part in determining how many, what placement pattern and what snow guard will be most effective."

There's even more science involved. Walberg says that the placement distance of the snow guards from the eaves of the roof is a function of "eave to peak distance, pitch and snow load." Plus, there are different considerations if you're installing snow guards with synthetic shake roofing versus synthetic slate shingles.

"We're specifying a job in Minnesota right now with Bellaforté Shake," says Walberg. "For that project an RG10 snow guard is most effective because it has a larger and higher pad face. If the same house had Bellaforté Slate roofing, we'd most likely specify the SnowTrapper ST9 product because they're a lower profile snow guard and work well with the Bellaforté Slate product."

Learn more about DaVinci Roofscapes.

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