Ice dams form due to uneven roof heating. That is a simple explanation for a complex interaction involving snow cover, heat loss from a building and temperature changes outdoors.
The problems caused by this complex interaction may include damage to paint or exterior siding and compression of wall installation leading to decreased energy efficiency in a system that is already not operating efficiently. Leaking water can also stain interior ceilings and walls.
Damage to walls or ceilings can be “covered up” with fresh paint. But the dampness can lead to the growth of mold or mildew, which will eventually stain the new paint. Mold and mildew growth in the home is a cause of allergies and other illnesses.
Icicles are a sign that the roof has the potential to form an ice dam. Higher temperatures near the top of the roof cause snow to melt. Overhangs are typically cooler. The melt water freezes. Hanging icicles typically form first. The icicles are sometimes lovely to look at but they are a bad sign for the building owner.
If it snows again, the weight forces the melt water through the roof. That’s why the ice is a major problem of roof leaks. The melt water cannot get past the ice dam as easily as it can get through the roof.
There are several steps you can take to prevent the formation of an ice dam. Some of these steps should be taken before the season’s first snowfall.
An effective attic ventilation system helps in some areas. Mechanical attic ventilation is not a solution in areas where snowfall is heavy. In Minnesota, for example, mechanical air ventilation systems can create additional problems such as moisture in the attic. Natural (non-mechanical) attic ventilation systems are more effective for keeping the attic space dry and preventing heat buildup in the summer.
Any vents or pipes on the roof can be potential problems. Heat will rise from inside the building and through the openings causing uneven melting. Moving vents to the walls of the building is one solution. Additional insulation or weatherproofing at the point where the pipes or vent system passes through the ceiling of the building is another option. The goal is to make the ceilings as air tight as possible.
If you notice that there is uneven melting on the roof or you see icicles hanging on the edge, the immediate step to take is to use a roof rake to get the snow off of the roof. Use caution to avoid taking a fall. A roof rake has a very long extending handle and can be used from the ground in most situations.
If you can see an ice dam, you can hose the area with tap water on a warm day to melt away the ice. You will want to work upward from the lowest edge where the icicles are hanging to create a channel to allow the melt water to escape. This is a temporary solution at best and you can save yourself from future roof repair problems. As soon as the weather clears, you will need to take other measures to prevent heat loss that contributes to ice dam formation.