What is an Ice Dam?

diagram showing how ice dam is formedAn ice dam is a ridge of ice that causes water to be trapped behind it. This results in water being forced into areas that your roof and gutter system was not designed to handle.

  • Ice dams form at roof edges whether you have gutters or not. Gutters are not the cause of ice dams. Melted snow and below freezing temperatures at the roof edge are the primary cause of ice dams.
  • Ice dams form in valleys (generally near the bottom or exit of the valley) due to snow compression, heavy drifting and obstructions. Valleys concentrate the amount of water present because they collect water from larger areas above them.
  • Ice dams can form anywhere melted snow can refreeze.
  • Icicles usually indicate an ice dam formation has occurred.

Ice dams are the result of snow melted by:

  • Heat loss from the conditioned area of the home or business into the attic cavity which warms the roof from underneath.
  • Inadequate levels of insulation allowing conducted heat to transfer into the roof structure.
  • Temperatures fluctuating above and below freezing.
  • Solar gain – the roof surface being warmed by the sun even though temps are below freezing. This can occur even at temperatures below 10F.
  • Poor or non-existent ventilation.
  • Roof ventilation that is covered by snow will not allow trapped warm air to escape. Also, the process of the snow melting from around ridge ventilation creates meltwater which can lead to ice dam formation.


Edge Melt Systems have the best products to prevent ice dam formation and protect your home.

Edge Melt Systems Product Line


Understanding the causes of your ice dams will help in solving your ice dam problems.


A home with ice dams and heavy icicle formation

Ice Dams are often accompanied by icicle formations