BoomerGirl Diary

Many of us love the look of icicles hanging down in front of our windows during the winter, but few realize that the ice dams on the edge of the roof may actually be causing structural damage to our home, and/or negatively be impacting our home’s indoor air quality.

An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow (water) from draining off the roof.

The water that backs up behind the dam can leak into a home and cause damage to walls, ceilings, insulation and other areas.

For an ice dam to form, there must be snow on the roof, and, at the same time, higher portions of the roof’s outside surface must be above 32 degrees Fahrenheit while lower surfaces are below 32 degrees Fahrenheit. When the snow on a roof surface that is above 32 degrees Fahrenheit melts, water flows down the roof and reaches the portion of the roof that is below 32 degrees Fahrenheit and freezes, creating the ice dam.

The dam grows as it is fed by the melting snow above it, but it will limit itself to the portions of the roof that are on the average below 32 degrees Fahrenheit. So the water above backs up behind the ice dam and remains a liquid. This water finds cracks and openings in the exterior roof covering and flows into the attic space. From the attic it could flow into exterior walls or through the ceiling insulation and stain the ceiling finish.

Preventing ice dams

Ice dams can be prevented by removing snow from the roof, which eliminates one of the ingredients necessary for the formation of an ice dam.

A “roof rake” and push broom can be used to remove snow but may damage the roofing materials.

In an emergency situation where water is flowing into the house structure, making channels through the ice dam allows the water behind the dam to drain off the roof.

Hosing with tap water on a warm day will do this job.

Work upward from the lower edge of the dam. The channel will become ineffective within days and is only a temporary solution to ice dam damage.

Be safe

Any person on the roof during the winter or performing work on the roof from below is risking injury and risking damage to the roof and house. You may want to hire a professional to carry out these jobs.

Long-term actions for preventing ice dams include increasing the ceiling/roof insulation to cut down on heat loss by conduction so that less warm air flows from the house into the attic space.

Because increasing insulation will decrease the amount of snow that melts off the roof, there will be an increase in the snow load that your roof has to carry. Can your roof carry the additional load? If it is built to current codes, there should not be a structural problem. Roofs in Colorado, like the rest of the home, should have been designed to withstand expected snow loads. If you aren’t sure, a professional engineer should be able to evaluate the structure of your home and answer your questions about the strength of your roof.

Mold, mildew, air quality

Moisture entering the home from ice dams can lead to the growth of mold and mildew, and these can cause respiratory problems.

It is important that the growth of mold and mildew be prevented which can be done by immediately drying out portions of the house that are wet or damp.

Interior damage should not be repaired until ceilings and walls are dry. In addition, interior repair should be done together with correcting the heat loss problem that created the ice dam(s) or the damage will occur again.

(Modified from University of Minnesota Extension publication “Ice Dams,” 2007.)