Excess accumulation of snow and ice is one of the most common weather-related problems that steel buildings face. Although most building codes require that a building’s structural design supports some snow and ice accumulation, there are times when weather conditions will test the limits of these requirements. Snow and ice tend to slide off steeper and warmer roofs but remain on colder or previously covered roofs with low slopes. Failure to remove excess snow and ice accumulation significantly increases the load, which in turn can cause personal injury as well as damage to the structure of your office, warehouse, barn, or other building.

How Much Snow and Ice is Too Much?

The density of snow on the roof of a structure usually ranges from 16 pounds per cubic foot to 30 pounds per cubic foot. However, it is tricky to specify the exact depth and density of snow that a building can support. The weight of snow and ice can vary based on conditions that exist during and after precipitation. Fresh snow weighs as little as 10 pounds per cubic foot, but it becomes heavier with water as it compacts. Furthermore, as the snow on the roof melts, the density can increase because not all of the water from the melted snow will drain off the roof. Instead, the underlying snow and ice will absorb the water. In addition, whenever it rains on top of the snow, the underlying snow soaks up the rain like a sponge, which increases the weight load. These variations in density can easily cause the weight of snow and ice to approach the density of water at approximately 62 pounds per cubic foot. Due to the expansion of freezing water, snow and ice density will rarely equal that of water. These conditions, however, should still be monitored carefully.

When Should You Remove the Excess?

Although it is hard to determine the exact depth at which to remove snow and ice accumulation, an approximation is helpful. It is usually a best practice to clear roofs of accumulated snow and ice once more than half of the maximum depth has been reached. You can find out the depth maximum of your building by contacting the party who designed and constructed the building. The maximum depth is usually calculated based on the density of the snow accumulation and the design snow load of the building. Based on this information, you can make some approximations. If a warehouse can handle up to 30 pounds per cubic foot of snow, then 18 inches of snow at a density of 20 pounds per cubic foot could overload the building, especially in wet conditions. The accumulated snow and ice will most likely build up in: valleys, lower roof levels, parapet walls, dormers, and firewalls.

Tips for Safely Removing Excess Snow and Ice

Safe removal of snow and ice accumulation will reduce the risk of overloading your building. Here are some general tips for safely removing accumulated snow and ice from your steel buildings. Due to the nature of this task, however, it is highly recommended to consult with a qualified structural building engineer before beginning.

• Remove all hanging icicles. These icicles can get very heavy, especially when the snow has accumulated on top of them. Exercise extreme caution so as not to damage the building or harm pedestrians below.
• If possible, avoid getting on top of the roof. One way to avoid working on top of the roof is to use a dragline. If you must work on the roof, however, work with someone else for added precaution. While working on top of the roof, use extreme caution when working along the edges. Even on a roof with a low slope, one misstep on a small patch of ice can cause an injury.
• Always place ladders at the end of the building. Falling snow and ice can easily dislodge a ladder from a building and cause serious injury or even death.
• Remove snow and ice in a balanced manner. Don’t remove all of the snow and ice from one area and then go to the next area. Avoid making piles of snow all over the roof. Instead, gradually reduce the load by removing the layers of snow and ice across the entire working area in a balanced manner, and remove the snow in the direction of the roof’s structure. For sloped or gable roofs, this means starting at the beginning of ridges and then working your way towards the eaves of the structures.
• Avoid damaging the roof panels, mechanicals, fasteners, and other peripheral structures. When removing snow and ice, exercise care when working around HVAC units, ventilator bases, pipes, electrical wiring, etc. Damaging any of these structures, such as electrical wires, can cause injury and unnecessary repair costs.
• Never use metal shovels or other sharp tools on a roof. Don’t be tempted to use tools such as picks, axes, and metal shovels to break up the ice on top of the roof. While these tools can certainly make it easier to break up the ice, they make it even easier to damage your roof in the process.
• Watch out for pieces of snow and ice sliding down the roof. A single piece of ice can be extremely dense, and even if it falls from a low-slope roof, it can still cause serious injury to someone below.
• Watch out for light-transmitting panels. Snow and ice will often conceal the locations of light-transmitting panels. Therefore, be careful not to walk directly on light-transmitting panels. Also, be cautious of walking on an area that is adjacent to light-transmitting panels.

Snow and ice are normal occurrences in many locations. Resolving excess accumulation of snow and ice from the roof of your building is necessary for both your safety and the structural integrity of the building. For more information on how to safely remove snow and ice from your steel buildings, contact a qualified professional at Allied Steel Building today!