You may have a problem forming on your roof this winter that you never knew existed. Ice dams are ridges of ice that form at the edge of your roof. These dams prevent melting snow from draining properly. Often the snow melts during the day, then freezes again at night increasing the ice damming problem. As the water backs up behind the dam, it can begin to leak through the roof shingles. This water can cause damage to ceilings and walls or the insulation in your attic, creating mold issues. While the ice dam is not a problem itself, it can be creating damage you may not notice for weeks or even years.

How do ice dams form?

A combination of snow cover, rising and dropping temperatures and heat seeping through your roof from the attic all contribute to the formation of ice dams.

Unless you (or the previous owner) requested it NOT be installed, a rubber membrane may have been installed under the shingles on the lower three feet of your roof, preventing water from backing up and entering your home.

The improper installation of insulation can contribute to the creation of ice dams as well. Warmth leaks through the roof, adding to the cycle of melting and freezing needed for the formation of ice dams. This can even occur with insulation that has a high R value, if it was not installed properly.

One solution is to insulate the underside of your roof with a closed cell spray foam product reducing your heating (and cooling) costs and reducing the formation of ice damming.

Problems Associated with Ice Dams. 

  • Rotted decking, rafters or exterior and interior wall framing and sheathing;
  • Growth of mold that could result in respiratory illnesses (allergies, asthma, etc.);
  • Gutter damage as large icicles form and grow in weight.
  • Reducing your insulation’s effectiveness of insulation. If your insulation is wet, it won’t retain heat well. If it’s wet all the time, it won’t decompress even when it dries.

Prevention of Ice Dams

  • Don’t get on your roof to solve this problem; it could be dangerous.
  • Seal air leaks in your attic to stop warm-air leakage (the source of the problem), such as those surrounding wire and plumbing penetrations, attic hatches, and recessed ceiling light fixtures leading to the attic from the living space below.  Recessed “can” lights on the top level of the house can be a source of leaks.
  • After sealing leaks, add additional insulation in your attic.
  • Provide adequate attic ventilation so that the underside of the roof and the outside air are at the same temperature.
  • Consider adding a vapor barrier between the insulation and the ceiling surface.  This barrier will keep moisture and water vapor from entering the attic area.
  • Clean leaves and other debris from gutters before the first snow.