Madison, WI,
15:49 PM

Beware of Ice Dams

Protect your home from water damage this winter.


Icicles may give your home a quaint look in winter, but they’re symptomatic of a bigger problem – ice dams.

Ice dams can damage your home because they prevent melting snow and ice from draining properly. This melted snow can seep under your home's shingles, damaging your roof, attic, ceilings, insulation, walls and belongings.

What causes ice dams?

Ice dams form when attic air becomes warm enough to heat the underside of the roof, which in turn causes the snow on top of the roof to thaw. The melting snow runs down the roof until it hits an eave or roof edge that is below the freezing point. The melted snow refreezes and creates a ridge of ice – an ice dam – which blocks further runoff. As snow continues to melt, it has nowhere to go but up, where it starts seeping under the shingles and into the house.

Prevent ice dams in the first place

The best way to prevent ice dams is to keep the roof – and attic underneath – as cold as the outside air. Here are some steps you can take to keep ice dams from forming.

  • Use a roof rake to get the snow off your roof. By removing the snow, you remove the water needed to form an ice dam. Use caution not to damage shingles, which can become brittle in cold weather.
  • Have adequate insulation. Attic insulation should be at least 12 inches deep, installed without any gaps and in conjunction with a vapor barrier.
  • Check light fixtures, chimneys, bathroom fans and anywhere else heat might escape into your attic. Seal any openings with caulk, spray foam or weatherstripping.
  • If heat ducts run through your attic, make sure they’re well insulated to prevent heat leakage.
  • Insulate and seal all attic access doors.
  • Install peak or ridge vents in the attic to allow warm air to escape, and install soffit vents to allow cold air in.
  • If you’re installing a new roof, add a moisture barrier under the roof covering to help prevent water from seeping into your home.
  • Weather permitting, and if you can safely access your gutters and downspouts, remove leaves, sticks and any other debris. Keep them clear of snow and icicles throughout the winter.
  • Many sources advise against using salt or calcium chloride to melt snow on a roof, as these chemicals can damage gutters, downspouts and nearby grass and plants.

What should I do if I have an ice dam?

The best thing you can do is wait for warm weather to melt the ice dam, and take steps to keep it from getting worse – namely, removing snow from the roof with a roof rake and keeping downspouts clear. Going on the roof to chip away at it is not only dangerous, it can cause more damage to your roof. If you can't rake the snow off the roof and can’t wait for the ice dam to melt, hire a roofing company with the tools and expertise to safely remove an ice dam.

Check out these related resources:

How to Prevent Ice Dams

How to Avoid Ice Dams on Roofs

Avoiding Ice Dams (and Showers Indoors)

Tips for Winterizing Your Home