Ice buildup is not generally considered a hazard to your roof unless it becomes unusually thick. But an ice storm like the one in 1998 created two problems: weight and blockage. The freezing rain stuck all over roofs, creating ice dams which backed up the natural runoff of rain and melting ice. Flat roofs suffered serious weight problems due to ice accumulation, while sloped roofs tended to suffer more water-penetration damage.
The aftermath of the storm provided an opportunity to learn how to better deal with a similar situation in future. The Canada Mortgage and Housing Corporation (CMHC) conducted research to determine how best to remove thick layers of ice from roofs as safely as possible and with as little damage as possible.
It’s important to note that these techniques are for skilled tradespeople only. No ice problem on your roof is worth risking injury – or worse. In many cases, unless the ice is causing a structural problem, it may be best to do nothing at all.
Furthermore, tools such as hammers, shovels, scrapers and chainsaws, and items like shoes with ice spikes, can damage roofing materials or the structure below. Chemical de-icers can discolour shingles, break down membranes and corrode flashings and drains. De-icers can also damage plants on the ground.
In the event of an ice buildup on your roof, there are three things you should do.
First: Observe and evaluate the situation every day to see if the ice on your roof is causing a structural problem. From the outside, deflections of the roof, particularly along the ridgeline, could be signs of a structural problem.
You can also check for signs of damage from the interior if you have access to the attic. Structural problems sometimes show up as the appearance of cracks on interior walls or difficulty in opening and closing interior doors. Consult a qualified professional if a structural problem is suspected.
Second: Assess your capabilities and limits. If there is any question as to whether or not you have the necessary skills, capabilities and equipment to remove ice from your roof, be safe and hire a professional.
Do you have the tools to safely access the roof and to remove ice? Do you have the agility, balance and strength to work safely and efficiently on a roof? Can you remove the ice without it posing a hazard to you or others? Do you have help – both to remove the ice and in case you get in trouble? Removing ice from your roof is a dangerous task, so engaging a qualified professional is advisable.
Third: Remove as little ice as possible to solve the problem. Attempting to totally remove the ice has the greatest potential for damage to the roof and to people and property below. Often, clearing dangerous overhangs and icicles and making drainage paths is enough.
Two methods of creating drainage in thick ice on the roof include electric cables or chemical de-icers. If electrical power is available, this is the easiest and most effective method of creating and maintaining drainage paths on your roof. De-icers can also be effective, but they may need to be applied more than once to melt through to the roof and to keep the drainage paths open.
If you hire a company to remove ice from your roof, check their references to ensure they have the necessary expertise and equipment. Ice removal by inexperienced tradespeople could endanger you and your neighbours, put the workers at risk and result in damage to your roof.
Its important to remember that during freezing rain conditions that cause roof ice build-up, emergency medical help may not be able to get to you quickly, if at all. Simply staying off the roof and hiring experts to do the work can be the best option. To learn more about removing ice from roofs, CMHC has a free About Your House fact sheet called Removing Ice on Roofs. To order your copy, visit cmhc.ca or call 1-800-668-2642.
Mark Salerno is district manager for the Greater Toronto Area at the Canada Mortgage and Housing Corporation. You can reach him at 416-218-3479 or firstname.lastname@example.org.