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Ice Dam: a mass of ice formed at the transition from a warm to a cold roof surface, frequently formed by refreezing meltwater at the overhang of a roof, causing ice and water to back up under roofing materials. Ice Dams are functions of environmental conditions, attic and roof design, insulation, and ventilation.
Specialized ice and water barrier membranes are available which can be applied under shingles when installing a new roof.
Ice and Water Shield is a tough, pliable sheet membrane designed to help prevent moisture penetration and interior damage when ice dam buildup causes water to back up during the winter season, and helps protect against wind driven rain. Ice and water shield, along with a properly insulated and ventilated attic, will help minimize or prevent leaks caused by ice backup.
This waterproof underlayment can be installed in new construction or during installation of new roof, under shingles, tile, slate, metal and shakes, is compatible with accepted roofing materials, and provides an effective concealed waterproofing system without detracting from the roof or building design. Some cities now require the use of ice shield around the perimeter of your home when you install a new roof. A few of these include Bay Village, Berea, Brecksville, Broadview Hgts., Brook Park, Brunswick, Garfield Hgts., Independence, Lakewood, Maple Hgts., Medina, North Royalton, Olmstead Twp., Parma Hgts., Rocky River, Strongsville, and Westlake. Other area cities are recommending Ice and Water Shield but not yet requiring it.
Ice Dams are Damaging, Dangerous and Preventable. A cubic foot of snow can weigh as much as 30 lbs. Multiply that times the area of your roof and you get a good idea of the kind of strain that can result when snow piles up overhead through the winter. The longer it remains, the higher the moisture content and weight become. The buildup of moisture leads to the formation of ice dams. Ice dams can cause water to migrate into interior walls and ceilings. The damage to plaster, paint, wallpaper results in substantial repair costs. The risks don't end there. Water seeks channels. Often this leads to water following the path of electrical wiring to ceiling fixtures and wall sockets.
Roofs that "leak" in the winter (when there has been snow and ice), but have not previously leaked at the same spot during rain storms...are most likely not leaks at all. This condition is called "ice damming". It is a temporary condition and it occurs when snow and ice buildup on the roof. When the temperature warms up, the ice begins to liquefy. When trapped by layers of ice and snow, the water is forced up and under the shingles, over and around flashings and valleys, and behind the siding of sidewalls; leaving it to drain through the ceiling of your home. This is a common condition related to winter weather conditions, attic and roof design, insulation, and ventilation. It is often impossible to find or correct roof leaks thought to be related to ice damming during the winter. Once the snow and ice are gone from your roof, and the leak does not continue into the Spring during normal rain storms, you know you have an ice backup problem and need to take corrective action. Because so many different factors play a part in the formation of ice dams, most roofing companies can not guarantee to prevent them or warranty against damage they may cause. See below.
Ice Dam Prevention
Ice Dams are functions of environmental conditions, attic and roof design, insulation, and ventilation. Debris filled gutters can also contribute to the problem by allowing snow and ice to collect and buildup on your roof because it can not drain properly. Roofs with no or limited attic space can also cause problems. Improving your attic's insulation and ventilation is one of the most effective strategies for combating ice dams. The higher the R rating of the insulation the better. The object is to make the roof as uniformly close to the ambient outdoor temperature as possible. Homes in cold climate zones that receive significant snowfall should be protected with ceiling insulation that has an R rating of at least 38 and is about 12" deep. Seal openings around plumbing and wiring that will allow warm air to escape from below with aerosol foam (exercise caution, as this type of material expands after escaping the can).
Make sure that there is no insulation outside the outside wall of your house or above the top plate of your exterior wall. All insulation should lie on top of the ceiling and none of it should touch the roof. This allows the ventilating air to circulate under the entire roof so that it will stay at the same temperature all over. Good roof venting plays an important role in preventing the melting that feeds the formation of ice dams.
If it does not already exist, create a way for air to enter the attic through the soffit. Ideally, there should be an intake vent between each rafter tail. Better yet, you can replace the soffit board with material that has openings all along it, this provides a continuous intake vent. Depending on which you prefer, you can install vent screens that pop into holes you cut into your soffit with a hole saw, as well as the continuous vent material.
Ensure that the outlet vents - along the ridge or high in the gable ends, are open and free of any obstruction that might slow down the air that is trying to get out.
The best thing about good vent systems is that they adapt natural forces to our needs. Done right, they operate on their own with no electrical or mechanical power required.
Breaking Ice Dams
Even if you are able to eliminate or minimize the formation of ice dams, leaving large quantities of snow on your roof can result in structural damage and pose a risk to plants, pets and people if it slides off in mass. Once you've got water seeping into your house, you need to deal with the ice dam. Here's the challenge: you have to balance removing the ice dam and preventing further damage with the possibility of causing damage to the roof as you remove the ice. No solution is ideal. Do as little as you must.
Here are some ways to deal with the ice dam if there is water seepage. Be cautious: working on the roof or below it can be dangerous in the best of weather, and ice, cold, and snow can make it more dangerous. Roofing materials are more brittle in cold weather, and more susceptible to damage.
Best solution: Find a contractor. This is usually the best solution, as the professional will know what substances are safe and effective to use, and will know how to use ladders safely under these conditions.
Do not use hammers, picks, axes, or ordinary de-icing salt.
Set and secure any ladders properly.
Clear dangerous overhangs and icicles -- being cautious that you position yourself so these and other ice that may become loosened don't fall on you.
Remove snow from the roof behind the ice dam, to prevent further ice dam buildup and seepage. Use a roof rake or push broom. Use caution to avoid slipping and falling, and be careful not to damage roofing materials. A well designed roof or snow rake is the safest, most effective way to remove snow from roof areas.
When selecting a roof rake, keep in mind that even though it is as light as a feather as it falls, accumulated snow becomes heavy. Many roof rakes are lightweight and flimsy. Look for one that is sturdy and durable. Sharp edges can also cause damage to shingles and siding, so selecting one with rounded edges and wheels to keep the blade slightly above the roof surfaces is also a good idea. Be sure that the roof rake has an adequate reach - at least 16 feet - and that the pole comes in sections that separate easily for convenient storage.
Make channels in the ice so the melting snow can run off the roof.
If there's a dormer window above the roof, try running hot water from there.
Hose the roof with tap water from below on a warm day, in selected spots to make the needed channels.
None of these solutions is a permanent solution; if you have a problem with ice dams, you'll need to take action to prevent the problem from repeating.
Also please see this excellent article, including photos:
Copyright 2004, 2005 Mike Priebe Roofing, Inc
4355 Hickory Ridge Ave, Brunswick, Ohio 44212
(330) 273-2700 or (440) 582-1723
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