Snow, Ice Cause Concerns About Farm Buildings

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ST. PAUL, Minn. – Last weekend’s snowstorm in the southern part of Minnesota has resulted in significant amounts of snow on the roofs of agricultural and rural buildings.

University of Minnesota Extension climatologist Mark Seeley said, “The medium range forecast for Minnesota from Dec. 24 to Dec. 31 looks like more frequent and accumulating snow is on the way, so we will certainly be adding to our December snowfall total without any melting.”

Larry Jacobson, an agricultural engineer with Extension said that, because of the cold temperatures and a layer of ice, snow that fell on metal roofs is not sliding off like it normally does in the winter. “If the ice/snow layer on the roof doesn’t melt, each additional snowfall this season will intensify the problem,” he said.

Farmers and building owners should monitor the snow load situation on agricultural structures and take appropriate action. Jacobson asks that farm and rural property owners and managers check high-risks areas, and be extremely careful with snow removal.

Snow loads for agricultural buildings in much of southern and western Minnesota are generally around 20 pounds per square foot. More recently built buildings may have increased snow loads to 25 or even 30 pounds per square foot. Jacobson said, “No matter what the level, snow loads are not intended to last all winter; there is a fatigue factor. A roof may be able to support the designed snow load for several days or a few weeks, but probably no more than 30 days.”

Jacobson estimates that the “safe” amount of snow to have on roofs for extended periods is about half of the designed load, or about two feet of normal snow or one inch of ice and one foot of snow.

Safely remove excess snow as soon as possible. Generally there is some time between a large snowfall event and possible structural failure. Unfortunately, one good way to remove snow from a roof is to physically get up on the roof and push the snow off with a shovel and/or broom.

Safety is an obvious concern when working on a snow-covered and icy roof. Use ladders, safety ropes and take necessary precautions. Snow rakes also can be used to remove snow. When using a snow rake, use extreme caution when working near overhead electrical power lines. Also, avoid excessive scraping on the roof or trying to chip off ice. These practices can damage the roof and lead to a leaky roof.

There are other methods of removing snow and ice from roofs. One involves warming the inside of the building sufficiently with large heaters to melt the ice layer, and then waiting for the snow and ice to slide off. Obviously, a lot of heat is necessary for even a moderately-sized building, and it must be an open-trussed structure (no flat ceiling), and have an uninsulated metal roof. Caution is necessary to prevent large chunks of ice and snow that slide off the roof from falling on people, animals or equipment.

For flat ceiling buildings, putting heaters in the attic is generally not recommended because of the fire danger and the possibility of creating ice dams along the building's eaves.

For more information, visit University of Minnesota Extension’s website at www.extension.umn.edu/extreme-weather/winter-damage.

Sources: Larry Jacobson and Kevin Janni, professors and agricultural engineers with University of Minnesota Extension



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