TWO PIPE SNOW GUARD SYSTEM – When to use it.
article originally post on S-5! – http://blog.s-5.com/blog/snowguardsonmetalroofs-0 reposted with permissions
When it comes to snow guards, there is a common perception that “more is better”, such as “two pipes are better than one” and “three are better than two”. Many believe that because a snow bank is very deep, it should have a taller snow guard system—with more cross-members.
X-Gard 2.0™ two-pipe snow retention system
This rationale seems intuitive, but is actually a myth. To put things in perspective, a 70 psf snow load can easily translate to 8 feet of snow or more. Whether the system restraining it at its base is 4 inches high or 8 inches high is somewhat irrelevant to a snow bank of such depth.
20″ Blanket of snow on a metal roof with an X-Gard™ system, in the mountains of Snoqualmie Pass.
All snow retention systems work by engaging the snow bank at its densest layer, which is immediately adjacent to the roof surface. This layer is compressed by the weight of all the snow above it, thus achieving its higher density, which also increases its compressive, tensile, shear and cohesive strengths. All snow guards rely primarily on the compressive and cohesive strength of that lower layer. We have seen banks of snow 6, 8—even 12 feet (2.5-3.5 meters) in depth restrained by snow guard systems only a few inches in height, provided the system has sufficient structural capacity and has been properly tested and engineered to resist the vector loads to which it is exposed.
Sometimes, designers or building owners simply want to make an architectural statement that the building is well protected by calling attention to the snow guard system, and for that reason choose a very robust system that is intentionally more visible. This, of course is a matter of taste and aesthetic.
S-5!® offers many different snow guard alternatives, including those which are only a few inches in height and visually blend into the roofscape. For those who believe that bigger is better, or just want the visual impact of a conspicuously robust snow guard system, we offer some that are two cross-members in height using unique pipe designs, utilizing both 1 and 2 inch diameter pipes. (Note that adding a third or fourth pipe does not improve performance or structural capacity. In fact, it may reduce capacity due to the tipping moments introduced to the system with such heights.) Each of our systems is carefully designed and rigorously tested for structural capacity, and can be engineered to withstand any snow load with our online calculators.
That’s why S-5! has a well-engineered snow calculator to help you plan out your snow guard project. The calculator saves you time and money in the planning process, including an option to get a low cost certified engineer stamp on your calculations.