Preventing Ice Dams

How do ice dams occur?  They start when attic heat melts the snow next to the roofing.  The water then flows to the eaves, where it freezes and forms the ice dam.  As the process continues, the water/ice backs up under the roofing, causing damage.  Ice dams are common on houses with moderate roof slopes, limited insulation, and little ventilation.

Ice dams do not occur on unheated buildings, so the idea is to have a cold roof.  How to do this?  Make sure you have adequate ceiling and/or roof insulation and air flow in and out of the attic.

Insulation:  Ceiling or roof insulation of R-38 or more is the best.  Any gaps in the ceiling around wires, pipes, chimneys, etc. should be sealed before insulating.

Ventilation:  Most attics need about a square inch of ventilation for each square foot of ceiling, and vent areas should be placed low and high.  Plastic or cardboard air chutes can be installed between rafters near the soffit to prevent the insulation from blocking the air flow.

Temporary and Emergency Measures:  You can remove the snow with a "roof rake."  Don’t chop the ice or use a torch to get rid of the snow, you could damage the roof.  You can also use water from a garden hose or heater cables to make channels through the ice dam.

Of course, see your contractor for more detailed information and make sure you educate yourself before tackling any of these to avoid damaging your roof.  With snow and ice melting and refreezing this time of year, it’s a good idea to check it out!

Thanks to Inspeca-Homes, St. Paul.

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