Dangerous Snow Covered Roofs
Snow-covered buildings can be beautiful and picturesque. But heavy snow-fall can deliver a one-two punch to roof structures that are not capable of supporting the weight.
Record snow-fall in the New England region has led to a number of dramatic roof collapses in Maine and Massachusetts. Here in the Midwest, we also regularly experience heavy winter snow and ice.
Remember the two 10” snow storms in 1979? Both storms bore heavy, wet snow which caused many roof truss failures. In contrast, the 2011 Groundhog Day storm dumped 22” of snow, but it was very light and powdery. The storm did not have the serious impact on roof structures because the snow was light weight. It is the heavy, wet snow that we worry about when designing roof structures.
In a 2013 blog post, we talked about getting through the winter unscathed. We offered design strategies for managing snow and ice.
Building roof structures must be
designed to carry the weight of the snow. Snow drifting must be predicted and
figured in the calculations. The roof surface, drains, and flashing also must be regularly maintained to reduce the chance of roof collapse.
But even well-designed structures may fail under the weight of record storms. Rain-soaked snow on roofs may turn to ice if the temperatures drop. Ice dams may also form at the perimeter of the roof, putting undue pressure on the eaves and gutters. The weight of all this ice may put a strain on the roof structure.
Strategies to lessen the chances of roof failure
- Have the roof structure evaluated, based on current design loads and weather statistics. Older structures may benefit from additional structural support.
- Ensure the roof membrane, flashing, and insulation are in good condition. Roofing is the barrier that prevents snow, ice, rain, and wind from entering the building and harming the roof structure.
- Insulate the attic floor so that heat does not build up at the inner roof surface which encourages the formation of ice.
- Remove heavy snow from the edges of the roof, if conditions are safe to do so.
- Check for clogged roof drains and gutters. Be especially vigilant in the fall when leaves and debris can accumulate and block the drainage of roofs. Ice dams can build up and put pressure on the roof structure. You can help protect the roof and the structure underneath by adding the following elements:
- Ice and water shield is installed under roofing, at valleys and the perimeter of the roof, where the roofing material and configuration are more vulnerable.
- Heating elements can be installed where ice dams typically form. They melt the ice before it can build up to thick and heavy dams.
- Ice breakers are installed on the roofing surface, preventing large areas of ice to form.
- Raised grates are installed over roof drains to filter out debris and allow the flow of water.
Call us for advice about your specific roof structure.
