Ice dams are formed by the continuous melting and refreezing of snow on the roof. This is caused by heat escape, usually due to lack of insulation or the backing up of frozen slush from the eavestrough. Water from the melting snow flows under it until it reaches the unheated soffit area and refreezes. This causes a dam where it can easily push back up under the shingles and cause water to enter the attic causing damage to the interior walls, ceiling, insulation and of course the roof deck.
To reduce the likelihood of this occurring, consider doing the following:
- Keep the attic space cold by insulating it to prevent or reduce the amount of heat loss from the interior of the home, which in turn can melt the snow on the roof.
- Installing baffles when insulating to ensure air flow at the eaves.
- Ensuring that the eavestrough is lower than the roof line to allow snow and ice to slide off.
- Ensure the eavestrough is free of debris by regular cleaning or by installing Gutter Guard.
- Installing at least 3’ of ice and water shield at the eaves of all heated roof decks in conjunction with a metal drip edge or eavestarter. This creates a watertight envelope at the eaves above the eavestrough and greatly reduces the odds of an ice damming leak.