Too many of us remember the pretty icicles on our house last winter, they spelled trouble. That’s because the same conditions that allow icicles to form — snow-covered roofs and freezing weather — also lead to ice dams; thick ridges of solid ice that build up along the eaves. Ice dams can tear off gutters, loosen shingles, and cause water to back up and pour into your house.
Ice dams form when:
- Heat from the house warms the roof and melts the snow.
- The melting snow re-freezes on the cold edges of the roof, accumulates and forms an ice dam.
- The snow continues to melt, the water backs up behind the ice dam, flows under the shingles, and into the house.
You can prevent ice dams by keeping your roof surface cold so that the snow doesn’t melt.
- To do this, increase insulation, seal air leaks from the warm part of the house, and improve ventilation in the attic.
If you plan to replace your roof, install a water barrier under the shingles (sometimes called ice and water shield) so that even if an ice dam forms, the backed-up water cannot get into your house.
Fast Fixes – when an ice dam forms:
- Rake it – If you can stand safely on the ground and reach the roof, pull off snow with a long-handled aluminum roof rake. A rake with wheels won’t harm the roofing. Call a professional roofing contractor if you can’t reach the roof from the ground to deal with the problem.
- Blow in cold air – If water is leaking into the house, take a box fan into the attic and aim it at the underside of the roof where water is actively leaking in. This targeted dose of cold air will freeze the water in its tracks. This is just a temporary measure to halt the flow of water while you deal with the snow and ice dams on the roof.
Don’t chip at an ice dam: you can damage your roof even more, and you could hurt yourself by slipping and falling off the roof.
For more information that explains how ice dams form and how to stop them.