Ice dams cause ice and water to back up under the shingles and cause a leak. Some ice will form at the edge of the roof simply from natural weather cycles and this is generally not problematic. Problems occur when ice is formed from loss of heat within the building. This heat loss will melt snow. The resulting water will run down the roof until it reaches the unheated eave edge where it will re-freeze. This can form a significant ice dam with enough heat loss and snow cover. While keeping the roof shoveled does help as it removes the snow and keeps the roof deck cool, there are three factors involved in actually fixing the problem.
- Minimize heat loss - Areas around pipes and other penetrations from the living area into the attic should be air sealed. Insulation quality and depth should be verified to make sure it is adequate.
- Ventilation - Attics should be properly vented to allow cool air to flow along the bottom surface of the roof sheathing to keep it cool and eliminate snow melt.
- Ice and water barrier - An ice and water barrier should be installed on the eave edge. This seals tight to the roof sheathing and does not allow water to get into the attic even if it should back up under the shingles. This should be installed even if the other measures are taken. It is a last line of defense and ensures that any ice, whether created by your home or mother nature, doesn’t damage your home.
Gary Schwenn - Owner