Removing Ice on Roofs
The 1998 Ice Storm
The ice storm that hit eastern Canada in January, 1998 was a laboratory for concentrated research into severe ice accumulation on roofs.
Removing ice on roofs describes some of the techniques developed from the research for dealing with extensive roof icing and ice dam problems.
Please note: Some of these techniques are for skilled tradespeople only. No ice problem on your roof is serious enough to risk broken bones — or worse.
The balance between removing ice and damaging the roof
Thick ice is hard to remove.You must decide if trying to remove it will cause more damage than leaving it on the roof. Tools, such as hammers, shovels, scrapers, chain saws, and devices such as shoes with ice spikes can damage roofing materials or the structure below. Chemical de-icers can discolor shingles, break down membranes and corrode flashings and drains. De-icers can also damage plants on the ground.
What to do in an ice storm emergency
First: Observe and evaluate the situation every day. Is the ice causing a structural problem? Is there water damage? Do you have to do anything?
Second: Evaluate your capabilities and limits. Do you have the equipment, the agility and the help to work safely and efficiently? If you don’t, get professional help before the situation becomes urgent.
Third: To prevent damage, do as little as possible.Total clearing 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.
Recommended Procedures for Sloped Roofs
When is there a problem?
The lower the slope, the greater the weight problem. During the ‘98 ice storm many flat roofs had 15 cm (6 in.) of solid ice, while most sloped roofs had little more than 5 cm (2 in.). Most of the ice collected at roof junctions, behind obstructions such as chimneys or skylights, and at roof edges. Drainage, not removal, solved the problem in most cases.
The information in Signs of Stress will help you decide if weight is causing problems on your roof. If your house doesn’t show signs of stress, then there is no need to remove all the ice.
Drainage
On a sloped roof, your goal is to make drainage paths through the ice on the lower edge of the roof. That’s where most ice dam and water back-up problems occur. Always shovel off loose snow to expose the ice.
If you have power and electric heating cables, making drainage paths is fairly easy. Attach loops of electrical roof de-icing cables to one or more long boards. With ropes tied to the board and thrown over the roof, pull the board up beyond the ice dam, letting the electrical loops hang slightly off the edge of the roof (see Figure 1).
Figure 1: Cables secured to roof
If you want drainage paths higher on the roof, use bundled loops of electrical de-icing cables. They can be drawn high on the roof. Make sure that they hang off the edge of the roof so you get complete water drainage.
You can use chemical de-icers on the edge of the roof. Clear the snow. At about every three feet along the edge of the roof, break the ice crust just above the ice block on the edge of the roof. Put de-icer in each hole above the ice dam and in a vertical line down to the edge of the roof. Use noncorrosive de-icers (see De-icers) and use as little de-icer as possible. Repeat as necessary rather than overdoing it the first time.
Removal
Removing ice mechanically from a sloped roof is always dangerous — both for the person doing it and for the roof. Removing ice will probably invalidate your shingle warranty. If ice must be removed, have it done by a professional with proper equipment and training.
Researchers learned a great deal about removing ice from sloped roofs by mechanical means in the winter of 1998. The most important lesson: always start at the top and work down. Starting on the bottom can release ice above you that can slide down and hit you. Small bumps of ice that remain on shingles are caught by ice blocks sliding down. As they slide, they catch and rip off the shingles.
Working from the top down allows you to use the ice on the roof as a slide for the ice that is being freed. Use a sledge hammer rather than an ax.The flexibility of the roof deck will cause the ice to fracture and you will not cut into the shingles.
Freezing Rain
Freezing rain is caused when there is a particular atmospheric “sandwich” of cold and warm air. Precipitation, usually snow, is formed in cold air high up in the atmosphere. As it falls, it travels through a layer of warm air that thaws it into light rain. Just before it hits ground level, it moves into another layer of cold air that brings
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