What’s an Ice Dam?

What exactly is an Ice Dam? An ice dam is an ice formation that usually forms along the roof’s edge and restricts melting snow draining properly. Ice dams can also develop around skylights, vents, and wherever two sloping roof sides connect (such as valleys).


Insufficient attic insulation and inadequate ventilation cause the roof deck to heat up and melt the snow above. As a result, the melted snow trickles down the roof and becomes trapped behind the ice dam. This pool of water gradually turns into ice and further increases the size of the dam. The water backs up above the 6ft protective ice and water barrier on your roof and may seep into the home, causing damage to walls, ceilings, insulation, and other internal components.

How Does It Happen?

  • -Heat from inside the house rises to the attic via the ceiling, reaches the roof’s underside, and warms it up. This causes the shingles to warm up.
  • -Snow sitting on the now-heated parts of the roof melts, with the water flowing down the roof until it reaches a lower part of the roof that’s colder than 32F (usually the overhangs). Here, the water refreezes, starting the formation of an ice dam.
  • -As more snow melts and refreezes, the dam grows in size. Water now begins to pool behind the increasingly large ice wall.
  • -Eventually, the water penetrates through the shingles (or other roofing material) and through the roof decking into the attic. From there, it can seep through the ceiling, interior walls, and into the rest of the building.

The following diagram provides a more detailed illustration of this process:

If you are worried your home might have an ice dam, give our team call and we can inspect your roof for proper venitlation and create a solution that is best for your home!