Massive snow accumulation on a roof creates the potential for an unpredictable avalanche-like effect. Metal is a great choice for your rooftop. It has a long life expectancy and can stand up to the harshest conditions. It does have a low coefficient of friction though–meaning things (including snow) don’t stick to it very well. But the notion that snow is intended to slide off a metal roof is misguided and can be dangerous.  

It is a sudden release of snow off a rooftop. Falling snow forms a temperature-sensitive bond to the surface of a metal roof. As that roof is warmed, (through sun or building heat loss), the bond with the snow is broken and a thin film of melt water lubricates the roof. This sudden release from a rooftop can dump many tons of snow below the eaves in a matter of seconds, endangering building elements, landscape, vehicles and pedestrians.

Qualifying Snow Retention Systems for Metal Roofing, from the Metal Construction Association discusses the rooftop avalanche in the following terms:

Metal roofs provide durable, long-term solutions and have been preferred by many for use in challenging northern and alpine climates where snow and its migration on and from the rooftop is a normal occurrence. Such climates can pose unique challenges for any roof. Pitched roofs of a material that has a slippery surface can pose sliding snow and ice hazards below eaves. In many instances, snow retention systems are installed on these roof types in order to reduce the risk of sudden rooftop avalanche and mitigate the hazards present in the discharge areas below the eaves.

Snow retention helps preserve your metal roof and allows snow drifts and snow melt to exit the roof in a more controlled manner (i.e. in small amounts, evaporation or melt water), avoiding the potential calamity of the rooftop avalanche.

According to the Metal Construction Association's technical document Qualifying Snow Retention Systems for Metal Roofing, a snow retention system, also known as a snow guard system, is a series of unitized snow-guard devices or continuous assemblies installed for the purpose of retaining snow on a roof and allow the snow to evacuate slowly via thaw and sublimation rather than suddenly and unexpectedly via rooftop avalanche. 

Our two-part series is on the S-5! Snow Guard Calculator. Step 1 covers exactly why it is so important to engineer your snow guard system. In Step 2, we'll explain how to log on and get started with your calculation!

Snow retention systems go by many names in the industry. Roof snow fences, snow rails, snow stops, snow stopper, snow guards, snow clips, snow bar, and more. Regardless of the phrase, the intended purpose is the same: to reduce the risks associated with rooftop avalanches. By holding back the snow and encouraging it to leave the roof slowly through small amounts or melting, damage to walls and foundations can be reduced.

This is Part Two of a two-part series on qualifying snow retention systems.

Recap of How Snow Retention Works

In Part 1 of What’s on Your Roof? we discussed how, unfortunately, there aren’t any snow guard police out there patrolling the industry. This creates a two-fold problem: One, that you can’t count on there being building inspectors to check a go-to-market system for structural adequacy; and two, architects and installers of these systems can potentially be sued for personal and property damage from faulty snow retention systems they specify or install.

But the light at the end of the tunnel comes in the form of the recently published Qualifying Snow Retention Systems by the MCA (Metal Construction Association). This technical guide bridges the gap between the free-for-all snow guard market and building owners, installers, and architects, who demand knowledge, strength, and a well-engineered system. So, what exactly constitutes a well-engineered system?

At S-5!, we don’t recommend installing adhesive-mounted snow guards on metal roofs. From both an economic and design perspective, glued on plastic snow guards typically have low holding strength and are unable to handle harsh weather-related elements. The bond weakens over time and when it fails, the guard can rip away paint and protective roof coatings, potentially leading to corrosion.

Our new SlideShare offers the best ways to mount snow retention. 

When a snow avalanche falls off of a rooftop, it can damage anything in its path! This sudden release of snow can be dramatic—dumping tons of snow in mere seconds. Falling snow forms a temperature-sensitive bond to the surface of a metal roof. Then, when that roof is warmed, whether from the sun or from building heat loss, the bond between the snow bank and roof is broken and a thin film of melt water serves to lubricate the slide.

A several-ton blanket of snow suddenly sliding off the roof can have dramatic results on anything in its path—gutters, the roof itself, landscape, vehicles and even people. Once it is piled up down below, that same snow bank can continue to cause additional troubles (e.g. repeated snow removal; direct damage to building walls; indirect damage caused by funneling melt water into, rather than away from the walls and foundations, etc.).

The Reason for Roof Snow Guards

This is what makes snow retention devices desirable: They keep snow in its place allowing it to leave the roof slowly, either in small amounts, evaporation or as melt water, avoiding the potential calamity of the avalanche.

Learn more about the three methods available for mounting snow retention systems to metal roofs with our new SlideShare. Click here or on the link at the end of the SlideShare to read the entire blog. 

Clamp Mounted vs Structure Attachment vs Stick-On Snow Retention Solutions

Metal roofs are a smart decision. But with metal roofs, you must consider the risk of roof top avalanches. A quality snow retention system will help you maintain your roof, avoid personal and property damage, and efficiently and safely allow snow to melt off your structure. But there are a number of methods to mount snow guard systems. What is the best way?

In my eight plus years with S-5! the most common question we are asked is, “Which S-5! clamp do I use on my metal roof?” We will explore the tools available to choose the best clamp along with the various options and other variables to consider, such as what type of roof you are attaching to and what you are attaching to it: solar, snow retention, or some other rooftop utility.