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Saturday, February 6, 2010

Flat Roof Hazards with Heavy Snow Load

Buildings and structures with flat roofs are at a greater risk of collapse since the heavy wet snow has no room to slide off. This winter storm has left anywhere from 16 to 24 inches of snow on roof tops and the as additional accumulations is expects throughout the course of today. Fire/EMS Department officials are also concerned that the risk may rise as melting and refreezing of the wet snow will occur which increases the weight.

Light metal buildings will typically have less capacity to handle a high snow load. For flat roofs, the step-down area between roof sections is a potential source of roof overload because of the tendency for ice and snow collection.

Many new structures are built to withstand higher weight loads. The total accumulated weight of four feet of snow could be as high as 60 lbs per square foot of roof space, which is getting toward the limits of even the best designed roof.

If there's ice, it's much heavier, with one inch equaling about a foot of fresh snow.

The men and women of the Prince George’s County Fire/EMS Department warn residents not to venture onto your roofs as the additional weight may cause a collapse. Do not use water from a hose in an attempt to remove the snow as this will melt and refreeze as well as causing drains to become blocked; further complicating the situation.

The Fire/EMS Department discourages home and business owners from clearing snow off of roofs themselves. This dangerous activity involves placing a ladder against the structure, ascending the ladder and using a broom or shovel to push snow off of the roof. Many performing this task are tempted to enter the roof structure. DO NOT GO ON THE ROOF. Be warned that climbing a ladder and entering a roof structure already stressed by a heavy snow load has its own inherent dangers and is not recommended.

The Fire/EMS Department highly recommends that you contact a professional roof contractor that has the experience and tools to safely clear snow off of flat roofs.

If you are in a structure with a flat roof and hear cracking, popping or stressed wood/metal noises; evacuate the structure and call 911 from a safe location.

The Prince George’s County Fire/EMS Department has not experienced any roof collapses at this point.

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