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What is an ice dam?
Ice dams are ridges of ice that form at the edge of a roof. Having an ice dam will prevent melting snow from draining off the roof and the water will back up behind the dam and seep under roofing material. The water that is trapped behind and in the dam can leak into the structure and cause damage to walls, ceilings, insulation as well as other areas. If left untreated, the damages can be extensive and extend from roof to basement.
Effects of an ice dam
When an ice dam is present, the water and moisture entering the structure can lead to excessive mildew and growth of mold. Mold growth is known for causing respiratory problems as well as creating allergies to those who are continuously exposed to the spores.
What causes Ice Dams?
Snow cover, outside temperatures and heat loss interact/combine to form ice dams. For ice dams to form, there must already be snow on the roof and the higher portion of the roof must have a surface temperature above 32F while the lower portions of the same roof must be below 32F. These average temperatures must be sustained over a prolonged period of time. The snow on the roof surface that is above 32F will melt and as the water flows down the roof and reaches the portion of the roof that is below 32F, the water will freeze causing a build up of ice on the edge of the roof. This is the beginning of the dam.
The dam will grow as it is fed by the melting snow above it but will be limited to the portions of the roof that average below 32F. As the water starts to pool up behind and inside the dam, the water will find cracks and openings in the exterior roof material and will start to flow into attic space. From the attic, the water will likely flow into exterior walls of the structure as well as insulation in the attic. When wet, the ceiling insulation will leave water stains in the ceiling finish as well as promote the growth of mold within the walls.
Prevention of an ice dam can easily be accomplished by having a professional company such as Trade-Mark Construction (back link this to Trade-Mark Website) check a structure with a blower door test to find any inefficiencies in a structure. These tests work by depressurizing a structure and then using a thermal camera to find areas where insulation is poor.