Snow, ice dams, and weight concerns


The heavy amount of snow we have received over the past month or so has led to the buildup of ice dams and icicles on many homes and businesses.

The buildup of ice dams on the roof edges act as a trap for water that melts on the roof above and flows to the edge of the roof where it freezes. The other real concern is the actual weight of the snow itself. The amount of snow we have received is a concern, but it can be a bigger issue where the winds have caused the buildup of snow drifts on many roofs.


The weight of snow on area roofs has become a larger issue due to the rain we received. Some roofs of houses and farm buildings may have snow drifts that may be three or four feet deep. We normally don’t think of snow as being very heavy; however, light snow may weigh seven pounds per cubic foot, average snow may weigh 15 pounds per cubic foot, and drifted compacted snow may weigh as much as 20 pounds per cubic foot. A cubic foot of ice weighs 52 pounds. The concern here is that the weight of the snow and ice may become more than the roof trusses can support resulting in a roof collapse.

A snow rake may be used to remove snow or in some cases it may be necessary to shovel the snow off the roof. This should be done with extreme caution as it would be very easy to lose your footing and slide off of the roof. There are a large number of homes in our area that each year have very obvious walls of ice with associated icicles hanging from the roof edge. Ice dams are formed when the roof surface above the eaves is above thirty-two degrees resulting in the snow melting and running down the shingles.

When the water gets to the area of the roof over the eaves in weather that is below thirty two degrees the water freezes and over a period of time forms a wall of ice along the roof edge. 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°F. 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 will flow into exterior walls or through the ceiling insulation and stain the ceiling finish or more seriously result in severe damage to drywall and ceilings. Eaves troughs that build up with ice will sag or be broken away from the roof simply from the weight of the ice.

In homes with problems with ice dams there is usually insufficient insulation in the attic area resulting in heat loss which warms the roofline and then melts the snow on the surface of the roof above. Exhaust systems like those in the kitchen or bathroom that terminate just above the roof may also contribute to snow melting. These exhaust systems may have to be moved or extended in areas of high snow fall. 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 or the damage will occur again. Moisture entering the home from ice dams can lead to the growth of mold and mildew. These biologicals can cause respiratory problems. It is important that the growth of mold and mildew be prevented. This can be done by immediately drying out portions of the house that are wet or damp.