Tag Archives: snow guards

Snow Retention in Building Codes

For all of my friends in locales where it does not snow, you are welcome to take a nap through this article. For those of us who are seriously tired of winter, but choose to endure shovels and plows, please read on.

Now snow retention is a subject well ignored by probably everyone you are discussing a new barndominium, shouse or other type of post frame building with.


Fear you will go to a different provider if the price is a few dollars more! 

Hint: someone has not learned to present benefits and you do not know to ask what you do not know.

I have searched every IBC (International Building Code) chapter for a section I was just certain I had viewed in an earlier Code edition – preventing accumulated snow sliding off roofs, in particular at door openings. I even went so far as to post a query in a Building Code Forum I am a member of. Other forum members confirmed I will be futile in my search. However one of them did come up with a link to a very sad story: https://www.foxnews.com/us/2016/02/27/snow-from-idaho-cabin-roof-buries-3-children-1-dead-2-in-hospital.html

These could very well have been your or my children or grandchildren – or even an adult, in event of a large snow slide.

I will admit to being sensitive to snow killing people, especially loved ones, ever since my cousin Kim’s tragic death, due to lots of falling snow back in 1986 (read more about Kim Momb here: https://publications.americanalpineclub.org/articles/13198701502/Avalanche-British-Columbia-Selkirk-Mountains).

Snow sliding down mountains happens and is pretty hard to prevent in back country. Snow sliding off building roofs can be avoided and with it tragic events such as a child’s death.

How can snow sliding off a roof be prevented?

By using a properly designed snow restraint system.

A snow and ice retention system mounting to a steel roof has to resist forces of snow and ice pressure by transmitting those forces from a snow fence or snow guard through roofing and into underlying roof purlins.

There are building codes for building roof system wind-uplift resistance on metal roofs but there are not for describing “shear strength” resistance for fasteners used to secure snow retention systems to steel roof panels.

Failures in mounting systems for snow retention devices can occur if not adequately secured to the building structure itself. Damage can also occur if total snow and ice load bends or breaks the roofing.  

It is plausible high snow and ice loading near roof edge, imposed against snow guards, could provide a bending force pulling fasteners out of the roof deck, bending or damaging roof, and sending snow guards and snow and ice to the ground below.

I had a snow retention system failure occur on one of my own roofs, where snow brakes were installed with stitch screws to only every third high rib of roof steel. My particular case had a dropped shed roof on one sidewall. When the upper retention system gave way, it came crashing down upon the lower roof, denting it and subsequently carrying away the lower roof system.

Before any modifications are done to an existing roof, a structure needs to be reviewed to determine if it is designed to support the weight of snow remaining on top, rather than sliding off. Provisions of model Building Codes, allow for reductions in design roof load for snow sliding off, especially in cases of unobstructed slippery roofs (e.g. steel roofing).

If your building is designed with a Cs value of less than 1.0, then it is not a candidate for a snow retention system (you will have to dust off your building’s engineer sealed plans to check).

Snow retention systems can be as simple as steel trim snow breaks I have properly screwed down to roofs of my home and two post frame buildings at Newman Lake, Washington. Without them, our 7/12 slope roofs will allow 18 to 24 inches of snow to accumulate, before sliding off, speeding like an oncoming freight train. When a mass of snow of this volume hits ground, noise is both deafening and frightening and an impact would most certainly not be healthy for anyone hit by it.

Where should snow retention systems be used? In snow country, anywhere it can slide off onto a lower roof, people, closely parked vehicles or adjacent buildings and above sidewall door openings.

For extended reading on snow retention systems, please check out this article on snow brakes: https://www.hansenpolebuildings.com/2012/02/snow-brakes/

Snow Brakes Help Keep the Snow on Your Roof

I live in a lake side home, in the mountains. Typically it snows here in the winter. We are not talking a few flakes or a few inches….we are talking about feet of snow.

My garage is adjacent to the stairs leading down to the house, from our parking lot. The garage has a 7/12 slope steel roof. One might believe not very much snow will stay on a slick roof which is so steep. I fell into this category, until I first saw several feet on top of the roof. Then I closed the door of the garage and witnessed the snow coming off the roof like a freight train, burying my stairs in several feet of snow.

My back having learned the lesson the hard way, I came up with what I thought would be a solution the following summer – I had steel snow brakes added to my roof to keep the snow on. These are pieces of steel trim which screw onto the high ribs of the roof steel, keeping the snow on the roof…..until the snow got so deep it ripped the screws out of the steel, sending snow, snow brakes and my gutters plunging onto the stairs.

My eldest step-son teaches physics, so I am sure he will be impressed by my having used the laws of physics in coming up with a better solution.

Keep in mind, the correct snow guard solution involves holding back thousands of pounds of snow and ice. Done right, the property and personal damages from sliding snow are eliminated, removing not only the problems of removal, but also the potential liability risk involved if a person was to be hit by such an avalanche.

Back to physics, the most efficient design is a pad style snow guard with a three to five inch wide forward (uphill) mounted flat face, with solid support struts and base. Other shaped configurations have found to not be efficient at retaining snow, which is their sole purpose.

For strength, the guards should be made of either 100% prime virgin grade UV stabilized polycarbonate or American made 304 Stainless Steel.

The manufacturer should be able to provide independent test results and replace the product, in the event of a failure. The only thing worse than having to purchase a snow retention system… is having to buy a second one to replace the first one.

Snow guard layout is critical to performance. The best value will come with a professionally designed layout. Most often, companies will quote far too few guards to properly do the job, in order to be the low bidder.

A reliable layout will have multiple staggered rows of guards, with each guarded mounted in the center of the valley between the high ribs of the steel. The most common layout mistake is to mount a row near the eaves and call it good. This gives sliding snow a chance to build up velocity and damage the guards and allows too much load on the lower roof section, potentially causing a structural failure of the entire roof.

Proper snow retention layouts equally distribute the snow load across the entire roof.  They will have multiple rows and a staggered placement.

Also, and just as important, most steel roofs are designed with a snow load adjustment due to snow being able to slide off a slick surface. If your new pole building will have snow guards of any sort installed, it is essential this snow load factor be set to not incorporate this reduction.

Take it from me, the guy with the shovel and the sore back…if you are in snow country – put snow brakes on.  But have someone design your roof system so they do what they are supposed to…and hang up your shovel.