Snow retention codes do not seem to be a priority in the United States’ roofing industry. But it is very common to see snow and ice sliding off of a metal roof’s slippery surface. Snow and ice crush cars, and damages the roof, gutters, and landscape.  In some cases, snow and ice cascading off roofs have killed people. Codes for snow retention systems are essential to protect people and property from sliding ice and snow.

There are many reasons snow retention systems fail and why we need codes in place.  Some examples are:

PRODUCT FAILURE

This snow retention system was not engineered for some variable of the project that caused it to fail.

The snow guard was not strong enough to hold the load it was carrying.

Anyone can cast a wax snow guard, spread some adhesive on the bottom, and tell the consumer how to install it without any testing of the product or the system. Codes would provide a standard to ensure adequately designed products are utilized.

SHEATHING/ROOFING MATERIAL FAILURE

Roofing material is inadequately secured for the shear created by sliding snow.

If the roofing material is not securely fastened to the deck (specifically on standing seam metal roofs), added weight can cause the standing seam metal roof to slide right off, along with the rest of the roofing material and snow retention system. There is a code requirement in place for wind uplift on standing seam metal roofs, but not for shear strength.

Screws or fasteners pull out.

Sliding snow can be incredibly dangerous.

When installing snow retention on roof sheathing, the thickness and type of the sheathing determines the fastener pull-out strength.  If one is installing a snow retention system on 7/16-in. OSB board, the fastener will fail more quickly than when using ¾-in. plywood.  (See chart below.) When designing a layout for a project, many snow retention manufacturers do not test for these variations.  If the snow retention system was designed for ¾-in. plywood and the project is using 7/16-in. OSB board, the whole system needs to be redesigned.

The fastener does not penetrate the sheathing.

If the fastener/screw is not penetrating the sheathing, the snow guard will not have the holding strength for which it was designed.

ADHESIVE FAILURE

These plastic snow guards fell to the ground because the adhesive did not bond properly

When using an adhesive, if the surface is not free of dust, dirt, oil, or waterproofing; or it is not clean and dry, the adhesive will not adhere properly.
If the temperature is not above 50 degrees F, the sealant will not cure. If a load is placed on the snow guard before the 28-day cure time, the snow guard is more likely to fail. (This is according to the Technical Data Sheet  for SB-190)

SYSTEM FAILURE

The system is not designed for the roof slope and snow load.

When designing a snow retention system, factors change from project to project: the slope, roof type, sheathing type, and roof snow load.  If the snow retention system is not engineered for the variables of the project, it can fail.
Most snow guards are not tested to the fail point of the system.

Many snow guard manufacturers claim theirs are tested, and many of them are, but they are not tested to the fail point of the entire system.  The product may be tested to maintain its shape, but was it tested to stay on the roof?  It’s great if the product stays in one piece, but not if the fastener fails, the adhesive fails, and the sheathing fails.

A snow retention code needs to be put in place to help prevent injury to people and damage to property.

INSTALLATION FAILURE

The product was not installed to manufacturer’s specifications.

The manufacturer’s instructions need to be followed meticulously in order to ensure safety and to keep warranties in effect.  Many manufacturers have specific torque requirements, placement, and maintenance instructions.  If these instructions are not followed, the system can fail and the manufacturer is not at fault.

Obviously, there are valid reasons why the United States should establish codes for snow retention on roofs.  Why hasn’t this happened?  A few reasons could be:

1. Snowfall occurs in certain areas of the country but not nationwide; therefore, the demand for codes is minimal.
2. Not many deaths occur due to ice and snow sliding.
3. Property damage is localized.
4. The insurance industry is not pushing for this type of code.

There are many other codes in place to protect people and property; so why not for snow retention?  We have codes for wind uplift and ICC test standards for product failures due to wind and moisture penetrations, to name a few.  How many life threatening events need to occur before we do the right thing when it comes to a code for snow retention on roofs?

It’s time to make the invisible snow retention code visible.

References

1. Surebond Technical Data Sheet SB-190.

About the author

Terry E. Anderson has been in the roofing industry for over 35 years. He is the owner of Anderson Associates Consulting and president of T.R.A.-MAGE, Inc., a manufacturer of roof snow and sun accessories. Anderson was sought after to solve tile roof problems, eventually researching solutions to the frequent structural damage caused by sliding snow and ice. Traveling to Europe, Terry studied how the roofing industry there successfully dealt with snow and ice issues. Using his years of experience and research, he coauthored Concrete and Clay Tile Roof Design Criteria for Cold and Snow Regions. Anderson founded T.R.A. Snow and Sun, now in partnership with MAGE and known as T.R.A.-MAGE, and is recognized as a leader in snow retention systems. He is a member of RCI, WSRCA, and on the technical committee for the Tile Roofing Institute (TRI).

Published: Interface Dec 2011

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Every once in a while a customer will ask us why they should purchase our metal snow retention rather than the plastic ones they see. We typically don’t like plastic snow guards for many reasons.

TRA Metal Clamp-on vs Plastic Guards

Most plastics eventually become brittle when exposed to the sun.

Because of its tough nature, metal can withstand the sun’s destructive UV rays. Over time plastic will crack and deteriorate when continuously exposed to the sun. If you already have a metal roof, it simply does not make sense to put plastic on it. Metal snow guards will ensure that your metal roof is protected.

Cracked, Brittle and Broken “Plastic Snow Guards”

TRA’s metal snow retention systems are attached securely using a variety of durable and strong mechanical methods.

Unlike metal, plastic snow guards are usually attached to a roof using caulking, which is likely to fail for the following reasons:

• If the roof is dirty or wet when installing this makes the adhesive not adhere properly. When have you ever seen a truly clean roof?
• More common than not snow guards are installed at temperatures below 40 degrees.
• Caulking cure time can be more than 30 days above 40 degrees.
•  Over time plastic will crack & deteriorate when continuously exposed to the sun UV.

TRA C21Z Clamp-on with Ice Flags 

Unlike plastic, metal lasts.

Next time you are near a roof with plastic snow guards, see if any are missing and let us know!

We recommend only metal snow retention because we know it can properly protect those in and around your home. For extra protection, we engineer from the sheathing up with the fastener and provide a warranty on the entire snow retention system. Before installation, we engineer a specific layout to see that the system is exactly what you need for your specific location and weather. Contact us with any of your project details and we’ll provide you with the best snow defense system that’ll get you ready for winter.

Keeping snow and ice from avalanching off a roof requires a system of superior strength.  When strength really does matter to save lives and prevent damage to property, how does a home or business owner know what snow retention product is strong enough?

How does someone decide what product measures up?

How does one decide the best method of installing a safe and reliable roof snow retention system?

If your answer to these questions is, “I can find that out.  I’ll just look it up online under building codes or ask my roofing contractor.” 

Well, good luck.

There are NO codes for roof snow retention!  None.  Nil.  Nada.  (Our owner, Terry Anderson, is serving on a committee right now to finally establish standards.  Watch for updates on this in the future!)  If a contractor starts sitting codes or standards, be wary.  The contractor might have his own standards, and we sure hope they all do, but there are no national or international standards for snow retention.

This makes it very important for owners, architects, engineers, and contractors to take extra care when designing a snow retention system. At TRA Snow & Sun, we seek to offer high-quality snow retention devices ENGINEERED for the unique snow & ice and building conditions relative to each specific project.

Snow retention as a science has emerged as a technological know-how for human safety. The laws of physics have to be used when holding back lots of destructive snow and ice. Annual assets and personal damage from destructive sliding snow and ice is in the millions, however, the price of a human life is incalculable.  If someone dies as a result of no snow retention or faulty snow retention, the liability threat to household owners and business proprietors is astronomical.

By retaining snow on the roof of a building and allowing even snow melt-off, injuries to residents/guests and property below the roof of a building can be avoided, saving money and limiting the possibility of personal loss. By installing snow retention you can:

• Prevent danger to residents and guests.
• Prevent costly roof and property damage.
• Maintain safe access, keeping entrances/walkways free of snow and ice.
• Promote energy efficiency by retaining snow which is a good insulation blanket.
• Trust in the best with the highest quality snow retention devices.

How does one avoid the potential pitfalls of a bad snow retention product?

It can get perplexing with several hundreds of different snow guard types and designs to consider from. With a TRA snow retention system, you know you’re safe because we have gone through extensive product testing. Our products are built to last to the fail point of the snow retention system, not just the product. Unlike other plastic type snow guards that turn yellow and fail over time, TRA’s snow retention systems are superior in strength. Our superior snow retention is designed to manage snow migration on any type of roofing is made of stainless steel or brass.

TRA CLAMP-ON SNOW FENCE vs PLASTIC GLUE-ON SNOW GUARDS

In simple terms, a first-rate snow retention product coupled with a reliable and safe FREE engineered spacing layout will help lessen the legal responsibility related to the unexpected slid of snow and ice from roofs. All requesting clients can receive free engineered layouts within 2 working days for each project’s specific requirements. For a free layout, data sheets, specs & quote contact us at 855-542-1861.

Snow Retention Case Study – Providing Engineered Snow Retention Solutions for HALF THE COST!

TRA Snow and Sun solves problems!  It’s not just our motto to provide Engineered Solutions.  We really DO IT!

On an addition to a home in Northwest Montana with a high snow load (100 psf); how do you retain snow on a cedar shake roof with a 12/12 pitch, whilst keeping it economical, aesthetically pleasing, and in line with the existing design?

After reviewing their options, Vandelay Construction was ready to order from a competitor, but was concerned about the high cost of the snow retention system, so they did one last internet search of roof snow retention.  They found a project with TRA Snow and Sun snow retention in Bozeman, Montana, liked our product and designs, and contacted us.

Using the information the contractor provided to us, we increased the thickness of the copper from the standard ¼” to 3/8” and designed a 3 rail snow retention system (D3H Deck Mount Snow Fence) specific to the project – cedar shake, 12/12 slope, copper, attaching to 16” OC rafters.  Copper was used to match the decorative end caps on the heavy timbers in the construction of the building.

Not only did the homeowners get a beautiful, warrantied system, but OUR SYSTEM WAS HALF THE COST OF OUR COMPETITORS.

We love the result.  See for yourself.

At TRA, we provide Engineered Solutions to all kinds of problems.  Let us help you with your snow retention needs!

Installing a snow retention system on your next metal roof can provide protection for the building owner and extra income, credibility and market share for you.

As the winter build-up of snow and ice begins to thaw, and even in the dead of winter in some places, building owners run the risk of a heavy avalanche of snow or ice falling on property or people as it slides off the roof.  You can see “Caution: Sliding Snow and Ice” signs in front of some buildings every year and probably witnessed a YouTube video of this happening.  Deaths and injury occur every year when people are hit by the heavy ice and snow build-up.

Anticipating and addressing this liability with your customer can provide them with valuable protection from the risk of snow and ice damaging property or even killing a person and could establish you as the contractor that goes the extra mile for his customer.  It’s not a time consuming or expensive add-on when you follow some simple guidelines and understand the issues involved.

Metal roofs have different properties from other roofs when it comes to sliding snow and ice; namely, metal roofs shed it quickly with little warning!  This is partly due to the lack of friction provided by metal as well as its conductive properties.

There are several “Don’ts” when it comes to putting any type of snow retention on a metal roof:

• Be wary of gluing snow guards on the roof.  Adhesive-attached snow retention must be installed on perfectly clean surfaces and at certain temperatures.  Even when applying them correctly, glued-on snow retention devices they are vulnerable to release during freeze/thaw cycles.  Mechanically fastened snow fences are a better and less labor-intensive method
• Do not use dissimilar metals.  If your roof is steel, use steel snow retention.  Don’t put copper or aluminum on a steel roof and vice versa.  By mixing the metals, you risk galvanic action (corrosion).
• Never penetrate the roof system!  This will void the manufacturer’s warranty on the metal roof.
• Do not assume that you can place one or two rows of snow retention near the eave of the roof.  This is a common mistake and can result in snow fence failure due to using a system that was not engineered.  When the snow releases on this type of amateur design, it can take penetrations, gutters and the snow retention devices off the roof.  Sometimes whole panels slide off.  Various factors must be considered when safely laying out your snow retention

There are some basic “Do’s” to a good snow retention system on a metal roof:

• Use systems that clamp on seams.   Besides maintaining the manufacturer’s warranty by not penetrating the roof system, clamps with 3-4 ” of contact with the rib will provide more security for the snow fence system
• Clamps should attach under the hem on the seam.  This prevents twisting and detachment when the snow fence is under pressure from the weight of snow and ice.
• Part of the clamp should sit on the base of the metal panel.  This helps keep the clamp and rib stable and upright, preventing the rib from bending sideways.

The Importance of an Engineered Layout

Snowload -Either listed on the plans or obtained from the local building department.Engineering the snow retention system is of paramount importance to protect the roof system, the owner and you.  Don’t be afraid of the word “engineering!”  Some reputable roof snow retention companies provide this free.  All it takes is gathering a few facts:

• Roof Slope – Obviously a 12/12 sloped roof will need a different layout than a 4/12 but the actual layout should never be left to guesswork.
• Rib Type – Different clamps are designed to work with different rib types.
• Rib Spacing – Rib spacing affects the number of clamps needed.  The strength of the snow fence depends on how far apart the clamps are spaced
• Method of Panel Attachment – If a panel is attached with a clip which does not stop vertical movement, the snowload can cause the panel to fall off the roof.  Knowing how the panel is attached will affect what type of snow retention to use.
• Eave to Ridge Length – This affects how much snow that area will be supporting which will determine the number of snow fences needed up the span from eave to ridge.

Correctly installed snow retention is a good idea for the owner because it protects property and people from significant damage or even death.  By adhering to a few simple Do’s and Don’ts and using an engineered layout, it could also be a significant way to enhance your business.

Terry Anderson has been in the roof consulting and roof accessory business for over 30 years.  He is a Registered Roof Consultant, member of TRI and co-author of Concrete and Clay Tile Roof Design Criteria Manual for Cold and Snow Regions and the owner of several roof accessory patents including the original Snow Bracket and Ridge Riser®.  His company, TRA Snow and Sun, Inc. manufactures snow retention devices for all types of roofs, solar mounting systems, and flexible ventilation and flashing products.

Published: Metal Construction News April 2014

Did you know that venting underneath the roof surface can prevent problems with condensation, ice damming, and increase energy efficiency?  A ventilated system causes warmer air to move through the system and escape through the ridge while cooler air enters at the eave.  This phenomenon has tremendous benefits and an excellent payback.

Condensation

A brief lesson on condensation and dew point temperature:

Condensation occurs  when dew point is reached.  What  is dew point?  Dew point temperature is the point at which saturated air can no longer hold water in the form of vapor and it condenses into water droplets against a cool surface.  We’ve all witnessed this phenomenon when the air against a cold glass of ice water forms droplets on the outside of the glass.  The same thing can happen as warm vapor-filled air escapes up through our ceiling and into a cold attic or on to the back of a cold roofing product.  Ventilation provides a means for that water vapor to escape before it condenses in an attic or on the backside of a roofing product, like a metal panel.

How many of us have had that moment lying in bed staring at the ceiling and we see that brownish water spot on the sheetrock and think.  We think, ” ____(insert expletive here), a roof leak!”  But it might not be a “leak.”

Often water damage perceived as a roof leak is actually caused by condensation within the attic, walls, or underneath the roof material.  If water vapor accumulates in any of these areas it can condense to form water droplets, which will eventually cause serious damage to wood, insulation, sheetrock, etc.  In coastal areas, the damaging effects of water condensing under the metal panel is intensified by the corrosive nature of the humid air and salt.  That moist air needs a way to escape and one way to assist with this problem is by ventilating.

Ice Damming

Ice dams are formed in snow climates when warm areas of a roof cause snow and ice to melt.  After melting the water then runs down the roof to an area where the roof is very cold, re-freezing into ice.  Eventually enough water has frozen, forming a wall of ice which prevents water from running down the roof surface.  This water inevitably backs up and finds a way into the building.  Ice dams can also cause serious problems when they eventually break loose and damage gutters, roof penetrations, and possibly people and property below.

The solution to ice dams is to keep the roof temperature even, preventing warm and cold spots.  Without ventilation, eave overhangs tend to be very cold and roof areas above the living spaces within the building tend to be warmer.  This scenario lends to the formation of ice dams.  By venting underneath the roof surface, any warm air escaping the building can exit through the ridge while being replaced by cooler air entering at the eave.  This keeps the roof at an even temperature so that ice dams never form.

Although ventilation can help prevent the formation of ice dams it won’t prevent sliding snow which can still cause serious problems.  An engineered snow retention system should always be considered.

Energy Efficiency

If you have ever worked in an attic space on a hot summer day you know how miserable that is.  Obviously roofs get hot from the sun and that heat enters the building.  Metal panels as well as other roofing products radiate that heat to the surrounding air and materials.  If there is a vented air space underneath the roof material, then the heat exiting the material warms the surrounding air molecules.  The molecules rise, escape through the ridge and are replaced by cooler air entering at the eave.  This drastically decreases the heat that enters the attic space or building by as much as 50% according to studies done at Oakridge National Testing Laboratories.

This decrease in entering heat equates to savings in cooling costs.  Those same studies from the testing lab showed as much as a 25% decrease in cooling costs.  The resulting savings makes for an incredibly rapid payback to the cost of adding a vented space under the roof surface.  An added benefit is that we conserve our limited resources, ensuring  a better future for all of us and generations to come.

Doing It the Right Way

Many factors play into the design of a ventilation system including determining the height of the air space needed and the size of the input and exhaust.  Some rules of thumb when installing a ventilation system are:

1. Intake and exhaust should always exceed the size of your vented space
2. Intakes and exhaust should be increased in size to accommodate for losses  to function created by screening as screening can significantly reduce airflow.
3. The vented air space under the roofing product should be sized according to rafter length and roof slope.
4. Steeper slopes tend to vent better than lower slopes and shorter lengths also tend to vent better than longer lengths.  So, steep short lengths require less of a ventilation space than low sloped long lengths.
5. Cut up roofs with dormers and valleys also create challenges when designing ventilation because eave intake areas are limited.

When designing ventilation for your roof you should consult with an expert to get a properly designed system.

To sum it up, metal roofs benefit in many ways from a ventilation system.  A metal roof shouldn’t be installed without first giving these benefits consideration

Terry Anderson is CEO of Anderson Associates Consulting, Inc. and President of T.R.A.-MAGE, Inc.
He gives credit to Dr. William Miller of Oak Ridge Testing Laboratories and Dr Nigel Cherry of Redlands Testing Lab, London, for their work on ventilation.

Picture – Nomograph 4-21 from “Concrete and Clay Tile Roof Design Criteria Manual for Snow and Cold Regions” showing the height needed for air space based on slope and length of rafter.

Picture – “Ice dams and eave ice.jpg” showing a vented roof system in the background and a non vented roof system in the foreground.

By: Terry Anderson

Published: Metal Construction News January 9, 2012

Snow retention codes do not seem to be a priority in the United States’ roofing industry. But it is very common to see snow and ice sliding off of a metal roof’s slippery surface. Snow and ice crushes cars, and damages the roof, gutters, and landscape.  In some cases, snow and ice cascading off roofs has killed people. Codes for snow retention systems are essential to protect people and property from sliding ice and snow.

There are many reasons snow retention systems fail and why we need codes in place.  Some examples are:

PRODUCT FAILURE

This snow retention system was not engineered for some variable of the project that caused it to fail.

The snow guard was not strong enough to hold the load it was carrying.

Anyone can cast a wax snow guard, spread some adhesive on the bottom, and tell the consumer how to install it without any testing of the product or the system. Codes would provide a standard to ensure adequately designed products are utilized.

SHEATHING/ROOFING MATERIAL FAILURE

Roofing material is inadequately secured for the shear created by sliding snow.

If the roofing material is not securely fastened to the deck (specifically on standing seam metal roofs), added weight can cause the standing seam metal roof to slide right off, along with the rest of the roofing material and snow retention system. There is a code requirement in place for wind uplift on standing seam metal roofs, but not for shear strength.

Screws or fasteners pull out.

Sliding snow can be incredibly dangerous.

When installing snow retention on roof sheathing, the thickness and type of the sheathing determines the fastener pull-out strength.  If one is installing a snow retention system on 7/16-in. OSB board, the fastener will fail more quickly than when using ¾-in. plywood.  (See chart below.) When designing a layout for a project, many snow retention manufacturers do not test for these variations.  If the snow retention system was designed for ¾-in. plywood and the project is using 7/16-in. OSB board, the whole system needs to be redesigned.

The fastener does not penetrate the sheathing.

If the fastener/screw is not penetrating the sheathing, the snow guard will not have the holding strength for which it was designed.

ADHESIVE FAILURE

These plastic snow guards fell to the ground because the adhesive did not bond properly

When using an adhesive, if the surface is not free of dust, dirt, oil, or waterproofing; or it is not clean and dry, the adhesive will not adhere properly.
If the temperature is not above 50 degrees F, the sealant will not cure. If a load is placed on the snow guard before the 28-day cure time, the snow guard is more likely to fail. (This is according to the Technical Data Sheet  for SB-190)

SYSTEM FAILURE

The system is not designed for the roof slope and snow load.

When designing a snow retention system, factors change from project to project: the slope, roof type, sheathing type, and roof snow load.  If the snow retention system is not engineered for the variables of the project, it can fail.
Most snow guards are not tested to the fail point of the system.

Many snow guard manufacturers claim theirs are tested, and many of them are, but they are not tested to the fail point of the entire system.  The product may be tested to maintain its shape, but was it tested to stay on the roof?  It’s great if the product stays in one piece, but not if the fastener fails, the adhesive fails, and the sheathing fails.

A snow retention code needs to be put in place to help prevent injury to people and damage to property.

INSTALLATION FAILURE

The product was not installed to manufacturer’s specifications.

The manufacturer’s instructions need to be followed meticulously in order to ensure safety and to keep warrantees in effect.  Many manufacturers have specific torque requirements, placement, and maintenance instructions.  If these instructions are not followed, the system can fail and the manufacturer is not at fault.

Obviously, there are valid reasons why the United States should establish codes for snow retention on roofs.  Why hasn’t this happened?  A few reasons could be:

1. Snowfall occurs in certain areas of the country but not nationwide; therefore, the demand for codes is minimal.
2. Not many deaths occur due to ice and snow sliding.
3. Property damage is localized.
4. The insurance industry is not pushing for this type of code.

There are many other codes in place to protect people and property; so why not for snow retention?  We have codes for wind uplift and ICC test standards for product failures due to wind and moisture penetrations, to name a few.  How many life threatening events need to occur before we do the right thing when it comes to a code for snow retention on roofs?

It’s time to make the invisible snow retention code visible.

References

1. Surebond Technical Data Sheet SB-190.

About the author

Terry E. Anderson has been in the roofing industry for over 35 years. He is the owner of Anderson Associates Consulting and president of T.R.A.-MAGE, Inc., a manufacturer of roof snow and sun accessories. Anderson was sought after to solve tile roof problems, eventually researching solutions to the frequent structural damage caused by sliding snow and ice. Traveling to Europe, Terry studied how the roofing industry there successfully dealt with snow and ice issues. Using his years of experience and research, he coauthored Concrete and Clay Tile Roof Design Criteria for Cold and Snow Regions. Anderson founded T.R.A. Snow and Sun, now in partnership with MAGE and known as T.R.A.-MAGE, and is recognized as a leader in snow retention systems. He is a member of RCI, WSRCA, and on the technical committee for the Tile Roofing Institute (TRI).

Published: Interface Dec 2011

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There are typically three different types of methods used when installing snow retention on a metal roof.

• Fastening through the panel to the roof deck or structure.
• Fastening to the panel, by mounting or clamping to the rib.
• Gluing or adhering to the metal panel.

Each method has its pros and cons, so when should each method be used? This question is usually left up to the roofing contractor or architect.

Roofing contractors should know that many snow retention manufacturers offer warranties with their products if installed to specifications.  Ice damming and snow and ice movement are two of the most common roofing problems in snow areas. Snow retention manufacturers have experience calculating loads and recommending proper layout and design for snow retention devices. Consulting with a snow retention manufacturer can save roofing contractors money, liability and ensure a high quality snow retention device that has a low risk of failure. Even snow retention manufacturers can have occasional failures due to the many variables when retaining snow on a roof, so the little extra money thatis spent for a warranted product is well worth the cost.

The first method of attachment is to fasten the device to the deck or into the roofing struc-ture with lag bolts, anchors, welds, etc. This method provides great strength to the product transferring the loads to the structure itself.  When installing large, bulky snow fences this is the only way to go; it is the only way to provide enough strength to the large load that will be placed at the fence. Unfortunately fastening to the deck or structure forces us to punch holes through the metal panel, this increases the potential for leaks and forces the contractor to seal or flash the holes in some way. Also, installing fasteners through the panel prevents expansion and contraction and can cause tearing, buckling or other forms of distortion to the panel. Many panel manufacturers will not allow their product to be fastened in this way.

The second method of attachment is to fasten to the raised rib by clamping or pinching.  This method also can provide great strength, and also does not penetrate the panel in any way, reducing the chance of leaks in the roof.  This allows the panel to expand and contract as well due to change in temperature. The only problem with this type of attachment is the loading; the load is not absorbed by the structure, it is transferred to the panel, so testing also needs to be done to ensure that the panel fasteners can support the weight. If no testing is done, occasionally whole panels will shear off the roof sending not only snow but sharp metal sliding to the ground below.

The third method of attachment is gluing or adhering the device to the panel. This method provides the simplest installation and usually the least cost. From our experience with snow retention glue-on guards, they are typically high risk. More glue-on snow retention devices fail than any other type because of the many variables of installation. Adhesives require, in general, an approximate 30-day cure time of temperatures over 50 degrees. Many mountain areas drop below 50 degrees every night even in the warm seasons. These devices are usually made of a plastic material. Plastics can be damaged over time by UV-rays causing color distortion and brittleness. Over time the plastic and adhesive break down and have a greater chance of failure.

To sum it up when holding a large amount of snow in one place (like a large snow fence at the eave) something very strong needs to be used and should fastened through the roof into the structure. In most cases a clamp-on snow fence is the best method of attachment. These are less expensive; sometimes multiple rows may be needed. And remember—the panel also needs to be fastened sufficiently to hold the weight. Glue-ons can be used to save cost and labor, but will not provide the strength, life and reliability that a clamp-on system will provide. But, on occasion glue-on snow retention is the best option. In most cases mechanically fastening to the rib provides the best bang for your buck. Just remember to always consult with one or more manufacturers instead of designing something yourself; if not you may end up paying for it later when you get back up on the roof for a repair. Most manufacturers will provide recommendations and design free of charge with a quote.

Published: Metal Construction News | April 2006

If you’re like most roofing contractors that work in the mountain regions of the United States and Canada, designing snow retention can be quite the chore.  Often, a call to a snow retention manufacturer leaves a roofing contractor wondering how they will explain to the customer the number of snow brackets needed throughout the roof.  It is often tempting for the roofing contractor to install just 1 or 2 or rows along the eave.  Here are a few reasons a roofing contractor may install insufficient snow retention:

• “That’s the way the architect drew it on the plans”
• “The owner can’t afford so many snow retention devices”
• “I’ve seen the snow here, I think it’ll work”
• “The snow retention manufacturer is just trying to make extra money, I don’t really need this many”
• “I’ve never done this before, I have no idea what I need, I’ll just put on some of these that I found at my local roofing supply store”

None of these excuses are worth the liability and risk of damage that can occur.  Designing snow retention is a refined science.  If the right steps are not taken to design a system properly it is very likely to fail.  Here is a list of some of the factors that must be considered when designing snow retention on any particular project

• Ground Snow Load
• Roof Slope/Pitch
• Roofing Substrate
• Roof Type

Studies have been performed across the United States and Canada to determine how much snow particular areas receive in pounds per square foot (psf), not inches or feet.  A certain depth of snow often weighs more in a particular area than another.  This is due to the different characteristics of snow; one foot of snow in the Sierra Nevada’s might be significantly heavier than one foot of snow in the Rocky Mountains.  Local building departments are familiar with this information and often have a code required snow load.  Obtaining the proper snow load information is the first step to designing a successful snow retention system.

These loads are then analyzed to determine how much weight is applied to the roof.  After some engineering calculations your snow retention manufacturer should be able to calculate how much force the snow is placing on the snow retention devices and therefore be able to determine how many devices are needed on the roof.  When too few snow retention devices are installed it becomes a matter of when and not if the snow brackets are going to fail, the math doesn’t lie, the snow retention will fail.  The first severe winter will take them out.

It is critical that these calculations are performed; if not designing snow retention becomes no more than a guessing game.  Often manufacturers receive calls from upset owners wanting to know why snow retention devices failed.  Many times, these customers are not compensated by the manufacture because the snow retention devices were not engineered and installed properly.

Here is one example we ran across recently.  For some unknown reason the roofing contractor decided that only 1 row of snow brackets was needed on this particular project.  During the first winter the snow brackets failed leaving the owner shaking his head and poised for more roofing expenses.  When snow retention devices fail, it becomes a matter of not just replacing the snow retention devices but also replacing other damaged items such as: gutters exhaust vents, roofing panels, etc.  In this case the owner was lucky and the sliding snow did no additional damage.

Unfortunately, the owner not only had to pay to replace the damaged snow brackets but he also had to pay for additional snow brackets so he would have enough to bring it up to manufacturer recommendations.  As you can see from the before and after photos the new design required 4 rows of snow brackets based on the design criteria for this area.  The good news is the owner now has a system that is warranted, but more importantly one that will work!  A quality snow retention manufacturer will warranty the product when installed correctly.

Here are some keys to follow when designing a snow retention system.

• Be prepared with an electronic or faxable roof plan showing the locations where you would like the snow retained.  If you don’t have one, draw one.
• Make sure you have obtained the key design factors (snow load, roof slope/pitch, roof type, roof substrate).
• Make sure that you are working with a manufacture that will design the system based on the criteria mentioned above, and will provide you a drawn out plan.
• Become familiar with the various products available and their strengths and weaknesses, a good manufacture will take time to explain these to you.

When the time is taken to design and install a snow retention system correctly the system pays for itself.  A properly designed snow retention system will prevent damage to the roof as well as people and property below the roof.  And with many snow retention manufacturers the design is free!

By: Jacob Anderson

Published: DesignandBuildwithMetal.com