Cherry and Clark Roofing - Greater Toronto Area

What are ice dams? How can they be avoided?

Ice dams are formed by continual thawing and refreezing of melting snow. Large masses of ice develop as snow on the upper part of the roof melts. The water runs under the snow and refreezes at the edge of the roof. Additional snow melts and forms pools against the dam gradually causing water to back up the roof often getting under the shingles and eventually leaking into the house.

Causes other than heat escaping from the home include:

• Bright sunshine melting the snow;
• Insufficient attic insulation allowing the heated air of the attic to reach the roof deck and melt the snow. (This could happen anywhere on the roof surface).
• Naturally occurring ice accumulation due to various weather conditions.
• Poorly placed gutters prevent snow and ice from sliding off the roof.
• Inadequate attic ventilation.

How to avoid ice dams:

• Install Waterproofing Membrane on eaves and in valleys to prevent water from penetrating the roof;
• Improve attic insulation keeping the attic space cool, thereby reducing the amount of melting snow;
• Improve attic ventilation to ensure that the attic remains cold;
• Make sure that your gutters or eaves troughing are lower than the slope of the roof allowing snow and ice to glide off.