Dealing With And Preventing Ice Dams

1/24/2019 (Permalink)

The cause of ice dams.

What Is An Ice Dam?

An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow from draining off the roof.  The water backs up behind the dam can leak into a home and cause damage to walls, ceiling, insulation and other areas.

What Causes Ice Dams?

There is a complex interaction among the amount of heat loss from a house, snow cover and outside temperatures that leads to ice dam formation.  For ice dams to form there must be snow on the roof and, at the same time, portions of the roof's outside surface must be above 32 degrees while lower surfaces are below 32 degrees.  The snow on a roof's surface that is above 32 degrees will melt.  As water flows down the roof it reaches the portion of the roof that is below 32 and  and freezes thus causing an ice dam. The ice grows as it is fed by the melting snow above it. The water backs up behind the ice dam and remains a liquid.  This water finds cracks and openings in the exterior roof and flows into the attic space.  From the attic it could flow into exterior walls or through the ceiling insulation and destroy those areas.

Prevention

Remove snow from the roof, eliminating the key ingredient to ice dams.  A "roof rake" and a push broom and be used to remove snow.  In an emergency situation where the water is already flowing into the home, make channels through the ice dam which allows water behind the dam to drain off the roof.  This is a temporary solution.