It's inevitable; winter along with its accompanying white stuff has arrived.  If you own or manage buildings in the Snow Belt section of this country, this information should be of interest to you.

For those of you in the north, snow and snow removal is something you have hopefully learned to live with. Snow removal operational plans are commonplace for roads and parking lots, but have you ever considered having one available and ready to implement to remove snow from the roof of your building? This is especially important on large span buildings such as gymnasiums, warehouses, "big box" retail stores, and shopping centers.

Each building in the north is designed to accommodate a specific amount of snow. This load is normally defined by the local building code. On occasion, in her effort to let us know who is in charge, Mother Nature dumps more of the fluffy white stuff than a building can handle; structural deflection, and in extreme cases, collapse, can occur. Each winter, roofs collapse because of excessive snow loads.

Determining a building's design snow load may be as easy as reading it off the building plans or talking with the "designer of record". On older buildings, it may require the services of a structural engineer to determine the in-place capacity of the structural elements and thereby allow interpolation of the original design snow loads. This load can then be used to establish a building's "safe snow load." Depending on the structure and building occupancy, the "safe snow load" could be 50% of the roof's actual design snow load. Snow removal would be initiated once the actual snow load exceeds this amount.

Design snow loads are measured in pounds per square foot (psf) and can range from 20 psf to over 70 psf. Fresh snow can range from 10 to 20 pounds per cubic foot. Snow that has partially thawed and then frozen may approach 40 to 60 pounds per cubic foot.

So you can see that determining if a roof is overloaded can and generally is part of the problem. Snow sampling procedures can be developed to measure and approximate the actual snow loads. Normally, this procedure would require taking several 12" x 12" full depth samples of the snow and weighing them. It is important to determine the load by actually weighing samples of the snow and not by measuring snow depth.

Due to the differences between fresh and frozen snow, there is no definitive correlation between snow depth and snow density.

In addition to exceeding the "safe snow load", other warning signs of overloading are:

One piece of information that is critical to the proper and safe removal of snow is the layout of the building's framing system. This layout must be available and easily viewed from the roof surface. Prior to the onset of inclement weather, the building column lines, location and direction of primary framing elements should be marked on the roof. This can usually be accomplished with spray paint on the backside of parapet walls.

Once it has been determined that the snow must be removed, the snow removal operational plan can be instituted. This is generally by a prearranged contract with a local roofing contractor. Snow removal is usually accomplished on a time and material basis, and can range from $0.35 to $0.50 per square foot and, as we all know, may need to be performed repeatedly over several days and weeks. Adding insult to injury would be if the roof had to be repaired or replaced because of improperly performed snow removal operations. A snow removal operational plan should be developed just like a roofing specification, clearly identifying who will do what, what procedures will be used in measuring actual snow loads, what type of equipment should be used, and in what sequence the operational plan will be accomplished.

Plans should also consider the need for emergency shoring at vulnerable areas and how all operations will be conducted in a safe manner. Specifically, the plan should address roof access and egress, edge fall protection, and appropriate cold weather clothing. The following are some specific dos and don'ts of the snow removal plan.

Snow removal is an inevitable part of winter. Are you adequately prepared for the safe and proper removal of snow from the roof of your building? Determining the building "safe snow load" is the first step in the development of a snow removal operational plan. Plans can be developed and bid out just like roof maintenance or reroofing projects, providing you with the confidence that next winter when Mother Nature comes calling, you will be ready.