The days following a snow storm, you may have noticed a leak or damage to your ceiling. If it has never appeared before, even during heavy blowing rains, then there is a good chance you have an ice dam.
What is an ice dam?
When snow melts on your roof and runs towards the gutters, the refreezing of the runoff near the roof eaves is where the ice dam starts. As this process is repeated every day until all snow and ice have melted, ice damming can cause damage to ceilings, walls, insulation and other areas. Because of the dam, ridge, rim, mounds or humps of ice, melted snow/ ice from the roof cannot flow down to the gutters and instead goes backwards or laterally. Shingles are designed to shed water, so backwards or lateral flow is what allows the water into the home and causes damage.
Why do ice dams form?
Most shingles absorb sunlight. Heat rises from your attic. These two factors cause the snow to melt on the largest areas of your roof first. The areas near the eaves and gutters, also snow covered, do not have the rising heat factor. Because the snow melts slower at the eaves, it will be the last to go. So the melted snow/ ice that is not drained from the roof will refreeze due to the temperature drop at the eaves or nightfall. If the snow on your roof is melting faster in comparison to other roofs in the neighborhood, potentially accelerating an ice dam problem, that is an indication your attic is short on insulation.
How to prevent ice dams
In this area, we have less than a handful of storms every winter. So shingle manufacturers do not require ice and water guard be installed between eighteen inches and six feet along all the perimeters of your roof. In other areas of the country, this is required by manufacturers or local building codes. We have only encountered one coil heating system installed on a roof designed to prevent ice damming on a northern facing low pitch back porch roof. Heat cable systems are expensive and not in use the majority of the year, thus making them a last resort in this area. If you have had a past issue with ice damming, make sure you have proper ventilation and insulation, have ice guard installed in the problem area, clear the area after a heavy snowfall with a rake or broom, but never put rock salt on your roof.
