Ice Dams

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Ice dams form when water reaches the edge of the roof and freezes or when gutters and roof valleys are full of leaves and debris and water from melting snow or ice runs off and refreezes at the edge of the roof or at the edge of the debris. The leaves and debris prevent water from rain or melting ice and snow from draining. This water then freezes and turns to ice when it gets past the exterior wall and hits a cold unheated roof edge or gutters which remain cold. When roof snow is melted by a warm attic space, the water runs between the snow and the warm roof surface. The ice dam grows as the snow and ice continues to melt, and as water continues to flow down the roof surface the water flow hits the ice dam it creates a larger and larger ice dam.

 Ice dams may also form on the unheated edge of a roof with no gutters where the melting ice or snow run off hits the cold unheated roof edge.

 An ice dam will work its way back up the roof edge or valley, get under the shingles, melt and leak into the exterior wall, home or attic causing extensive damage to the structure of the home or attic insulation.

 Roof snow or ice melts from the roof surface upward. There are a couple of reasons for this.

 First – the suns ultra-violet rays go through the snow or ice to the roof surface where they warm the roof surface, thereby melting the snow from the underside. The snow on top acts as an insulation blanket.

 Second – warm attic space. Homes with poor insulation and attic ventilation are more susceptible to ice dams.  Poor attic ventilation allows the roof deck to be warm. Attic warming from poor ventilation is made worse with the introduction of heat from the occupied floor below the attic including sources such as lighting, air leaks, ductwork, lack of enough insulation, etc.

 The attic needs intake adequate intake air vents (soffit vents) and exhaust vents to move the moisture in the air from the attic to the exterior of the home. These vents need to be checked annually to insure they are free of paint, insulation, wasp nest etc. In the winter time your attic should be the same temperature as the exterior temperature. I see a lot of gable vents without soffit vents. You need those soffits vents so that the air can be pulled through the attic.

 Keep your gutters and roof valleys clean. Keep all leaves and debris off your roof surface. Install adequate attic intake and exhaust ventilation.

 If you notice an ice dam forming its best to not chip it away as this could damage your shingles. Check your gutters and valleys and roof surface for any debris and if they are full of debris wait until the roof is safe to walk on to clean off the debris. Check your soffit vents and your exhaust vents to ensure they are working at full capacity. Have a professional contractor locate the cause of the ice damning and correct the problem.

 Remember when walking on a roof should you slip, the fall will be kinda exciting however the sudden stop will be a bugger, so leave it to the professionals as it might be more cost effective in the long run.