Don't let a collapse cave-in on your program
Most structural collapses that occur in a camp setting are caused by heavy snow loads that stack up on roof tops. A study completed by Curt Gooch, Sr. Extension Associate, Cornell University, states that the weight of 1 foot of fresh snow ranges from 3 pounds per square foot for light, dry snow to 21 pounds per square foot for wet, heavy snow. So hypothetically, if your roof measures 10 ft. x 30 ft., twelve-inches of wet snow could easily exceed three tons.
An effective loss prevention plan to prevent roof collapses due to snow needs to include monitoring upcoming weather events that might result in significant snow falls and having a response plan should it fall. The following article regarding snow loads is provided by FM Global and reprinted with permission.
Help prevent snow load roof collapse by taking these steps now
Resilience runs from the top down. In winter, that means the roof. Prepare now to stay in the clear during snow season. “Winter storms can become a routine occurrence,” says Katherine Klosowski, P.E., Vice President and Manager of natural hazards and structures at FM Global. “Yet snowstorms and deep freezes can still catch us off guard. If you’re unprepared, these storms can result in roof collapse and frozen pipes. Having a plan and implementing it can help keep you in business.”
Make these steps part of your rooftop snow removal plan:
Before a snowfall:
- Ensure you have and follow an occupational fall prevention plan that is compliant with local regulatory agency requirements before engaging in roof preparation activities.
- Clearly identify safety protocols and ensure they are followed.
- Train your emergency response team and contractors to properly remove snow.
- Ensure generators are working and their fuel tanks are full.
- Check roof drains and downspouts to ensure they are clear. Remove leaves, pine needles, and any other objects that would impede water drainage.
- Mark roof drains with a visible flag high enough above expected snow.
- Check condition of rooftop equipment and make any necessary repairs before snowfall and freeze.
- Check changes in roof elevation. Adjoining roofs of different heights can lead to snow drifting onto lower roofs, so these areas must be reinforced to withstand the greater weight.
- Clearly mark fire hydrants and fire protection system control valves to avoid damage from snow removal equipment. This identifies them for prompt snow removal along with access routes. “Performing this routine maintenance helps you avoid unpleasant business disruptions,” Klosowski explains. “One of the most critical items is also one of the easiest—keep the roof drains clear. It’s all about getting water off the roof.”
During a snowfall:Winter weather can arrive suddenly and squall relentlessly as wind blows and snow piles on rooftops. Klosowski cautions, “Wind gusts and whiteout conditions make it dangerous for people to be on the roof during a storm. Prepare to take action after the storm has passed.”
After a snowfall:
- Ensure you have and follow an occupational fall prevention plan that is compliant with local regulatory agency requirements before engaging in roof snow removal activities.
- Manually remove snow with shovels and wheelbarrows, and cart snow off the roof edge. Snowblower augers can damage rubber and plastic roof structures.
- Snowblower caution. If using a snowblower, ensure that the auger is set to the highest level to avoid contact with the roof. Set the blower discharge level high enough to clear the roof.
- Carefully remove ice using small tools. Ice choppers and ice melt can damage a roof.
- Check the integrity of roof overhangs and canopies that can buckle from the weight of snow and ice.
- Use an emergency, standby, or temporary generator and make sure the following circuits are included for heat:
- Heat tracing along the roof edge
- Dry sprinkler riser heater and air compressor
- Building heating system(s)
- Inspect roof for damage and make any necessary repairs when it is safe to do so.
“Roofs can handle light, fluffy snow. The danger comes with dense heavy snow or rain intermixed with snow -- along with repeated freeze and thaw cycles. Water ponds on the roof and snow soaks it up like a sponge. This adds a lot of weight.” Klosowski explains. Then there is this good rule of thumb: “Be wary of snow that makes good snowballs.”
Milder weather can put roof collapse from snow out of mind. Klosowski explains, "Roofs can handle routine snows. But if snow events continue and are followed by snowmelt and rain, that adds a lot more weight. Ponding rainwater can also cause collapse." Remember, when you protect your roof, you protect everything beneath it. Prepare now to take the load off before the snow flies.
Before allowing personnel or contractors on a roof, ensure that it has been designed to withstand the amount of snow expected in your geographic region and the actual amount of snow that fell, and add to that the weight of equipment and expected people on the roof. Buildings with metal roof systems are especially vulnerable if the purlins have not been adequately braced or otherwise designed according to the 1996 (or later) edition of the American Iron and Steel Institute Specifications for the Design of Cold-Formed Steel Structural Members.
If you plan to hire a contractor to manage your snow removal, there are certain steps you will need to take to make sure your business is properly protected. Learn what you need to know about working with independent contractors.
*Markel Specialty is a business division of Markel Service, Incorporated, the underwriting manager for the Markel affiliated insurance companies.