ICE DAMS - Causes, Removal, Damage, Prevention

Icicles hanging from a roof may look pretty but they may be an indication of  ice dams forming on the roof.  Ignoring them will not minimize the fact that the ice and water may be causing significant damage to the house.

Ice Dam Causes
When snow accumulates on a roof a cycle of melting and refreezing occurs.  The snow melt will refreeze at the cooler edge of the roof and create a ridge of ice commonly called an ice dam.   These dams will block water from escaping off the roof by creating a pool of water.  This water can sometimes leak into the soffit area or leak back under roof shingles and into the house creating damage to ceilings, walls, insulation, cabinets, flooring, and other personal belongings.  The warmer the attic the greater will be the amount of water from snow melt.  Though it is not always possible or even practical, one way to stop snow melt is to remove all the snow with the use of a snow roof rake.

Ice Dam Removal
Removing ice dams off a roof can be very dangerous.  Snow covered roofs can be very slippery.  Ladders can fall over because of slippery ground and ice on the gutter.  In addition, damage can occur to the roof while removing ice.  Immediate ice removal will however quickly stop the water coming into the house.  This can be accomplished by chipping a channel into the ice dam to release the trapped water.  Another way is filling a sock with one of the appropriate ice melt products and placing it on the ice dam to melt a groove through the ice that will allow the water to run off the edge of the roof.  Ice melt products may be harmful to the shingles or they may damage plants, read the packaging material carefully!


Ice Dam Damage
Roof shingles and gutters can be damaged by the ice dams.  Any wood that has become saturated with water is subject to wood rot.  The wet wood can also provide perfect conditions for the development and growth of attic mold (sometimes called black mold) or mildew.  Mold and/or mildew can grow in the attic, in damp wall cavities or grow on wet drywall.  Wet insulation can also harbor mold.  Mold removal can be very difficult as well as quite expensive.


The water running into the house can also damage walls, floors and floor coverings, cabinets and wood trim used around doors, windows, baseboards and ceilings.



Ice Dam Prevention
Ice dam prevention begins in the attic.  Since attic heat is a major contributor to the melting of snow on the roof and subsequently to the formation of ice dams, lowering the temperature should decrease the formation of ice on the roof.  There are 2 partners in this endeavor to prevent ice dams; attic insulation and attic ventilation.  The proper amount of attic insulation, combined with sealing all areas that may leak warm air into the attic, will help keep the attic cooler while sufficient attic ventilation will allow the warm air that does collect in the attic to be replaced with cooler outside air.

There are also some steps to be taken during roof installation that will help prevent ice dams but that will be the topic of another post.