An ounce of prevention... snow load loss

by Jaren Tolman, MBA, PE

With winter in full throttle, I'd like to remind readers of the dangers associated with heavy snows, specifically as they relate to older wood barns or out-buildings. Older wood barns or out-buildings are especially prone to the dangers associated with heavy snows. Many of these structures were built without a permit or design.

As heavy snows build up, there is no heat inside the building to encourage melt-off.  In addition, drifting snow accumulates and is not commonly cleaned from the sides of the building.  This encourages moisture degradation of the structure and, in essence, weakens it. 

These structures are candidates for collapse.  If you are using buildings of this nature, it is a good idea to maintain them throughout the year.   Metal roofing will help snow sluff off steep roofs.  Keeping the perimeter free of snow will help keep the wood dry.  As always, if you have any doubts, Contact an engineer to examine the site and make potential recommendations for repair. 

The picture to the left, shows a wood column and a 'kicker' that was framed into the column.  This 'kicker' supported a large portion of the roof loads.  The column here had fractured, not unlike breaking a stick over your knee.  Also note that the edges of the fracture are clean and the wood is bright.  Had this been an older failure, the edges of the fracture would have weathered to match the other wood shown in the photo. 

It is easy to see that this fracture was dramatic and occurred under heavy loading.  Additionally, I was able to obtain photographic evidence that the structure was intact and standing the previous summer.  

These clues - the point of fracture, the color and sharpness of the fracture, and knowing the structure was standing the previous summer all led me to believe the structure failed under heavy roof loads; and the likely candidate was snow.  A quick review of climatic data showed that the area had indeed received heavy snowfalls in late spring.  It was then concluded that the heavy snows were, indeed, the likely cause for the failure of the building.

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