Buildings and facilities often deal with snow piles during and after winter storms. While these piles look unsightly, they can also be risky for building occupants and visitors. Depending on the location and roof design, each building has a maximum snow load it can safely bear. Understanding this limit can help prevent damage and structural failures.
Roof Collapse
As winter snow accumulates, a building’s structure may be pushed to structural failure. It can cave in if a roof’s weight exceeds its design capacity. This can affect everything below it, from personnel and equipment to inventory and materials. A collapsed roof can lead to various expensive issues, including water leaks. This can wreak havoc on a facility’s interior, leading to mold and rot of the structural supports. To avoid these problems, a clean, unobstructed drain is crucial. But the most important consideration is determining how much snow a structure can safely support. The uniform load a structural design can bear is typically expressed in pounds per square foot. However, this doesn’t directly relate to the depth of accumulated snow.
Injury
Snow can be a major safety hazard, especially when it’s heavy. People can get injured by falling on icy surfaces, climbing ladders to hang holiday decorations, placing rooftop lights, and shoveling snow. Getting struck by a snow shovel might not seem like a serious injury, but it is responsible for thousands of emergency room visits each year and has claimed as many as 100 lives nationally. Shoveling snow causes lower back injuries, shoulder pain and neck injuries. The sudden exertion can also trigger heart attacks in individuals with preexisting conditions. Using roof snow load measurement can help determine how much snow your roof can safely hold without risking damage. It can also help you prevent water infiltration and structural damage.
Water Infiltration
The depth of snow on a roof and the density of that snow determines its weight. You can calculate the roof snow load using a simple formula and known snow volume. Choosing a building’s design snow load from the original structural drawings is easy. However, determining whether the current snow accumulation overloads an installation requires knowing the actual unit snow weight based on an accurate sampling of the existing conditions.
To obtain a sample of the actual unit snow weight, the sample must be taken at multiple locations throughout a roof area. This includes the areas against rising walls and parapets and roof-mounted mechanical units where snow tends to drift. The sample must also be weighed to determine the current snow load accurately.
Ice Buildup
The weight of snow builds up and compresses a roof system. This may result in ice buildup over time, seriously harming the structure and its contents. Ice dams form when heavy snow melts during the day and then refreezes at night, and they are particularly common in northern regions. This melting-freezing cycle causes water to work under the shingles and into the attic, significantly damaging ceilings, walls and contents. To sample roof snow load, facility maintenance teams can use a simple method that involves thrusting a metal rod or stove pipe into the snow until it reaches the roof structure. This is much safer than climbing on a roof and provides comparable results. The rod or tube is then weighed to determine the roof snow load.
Wind Damage
The force of snow accumulating on a roof can add up to significant weight. This additional weight may be exacerbated by wind, which can further weaken the structure and cause damage. A building’s maximum snow load is based on various factors, including geographical location, roof design, pitch, and building codes. A snow load calculator determines your home’s maximum allowable snow load. The key to calculating the correct roof snow load is knowing how much snow has accumulated, which is only possible through precise measurement. Factors that impact the weight of snow include depth and snow density. Fresh, light snow may weigh only five pounds per square foot, but packed snow can be twice as heavy. Temperature fluctuations can also cause snow to thaw and refreeze, changing it from light to denser wet snow.
