Roof Ice Damming
What is an Ice Dam?
An ice dam is the ridge of ice that forms primarily at the edge of a roof which prevents melting snow from draining as it should. An ice damn can do serious damage to your roof, walls, floors, ceilings, insulation and other areas inside your home. This is caused by water backing up behind the ice dam and leaking into the home. Sloped roof shingles are designed to shed water, not to prevent water from backing up under them. Ice dams can also destroy your gutters and downspouts. If the ice dam breaks free, it can pull shingles and gutters off with it and can damage anything it falls on too.
What Causes Ice Dams?
Ice dams are caused when heat escapes into the attic or roof space and the heat build up eventually melts snow on the roof. Water from melting snow runs down the cold surface of your roof and refreezes. As the cycle of freezing and melting continues, ice builds up and begins to dam. Sometimes the melting water backs up and finds it way under shingles and refreezes, lifting the shingles from the roof deck and creating a spot for water to enter your house. Factors such as insulation, ventilation, tree coverage, home architecture, snow cover, home owner lifestyle, and weather conditions all interact to determine ice dam activity on every home. No two homes are alike.
How to Prevent or Minimize Ice Dams
- Keeping your gutters clear of snow, including the bottom of the downspouts so that when the snow melts the water flows freely
- Sealing all points where warm air leaks from the living space into the attic
- Making sure you have a adequate bathroom fan that is in proper working condition and is hooked up accurately to your gooseneck
- Insulating the attic space well enough to prevent conduction and convection of heat through the ceilings in the living space
- Installation of proper ventilation in the attic to include soffit ventilation and ridge ventilation where applicable, to ensure heat that does sneak into the attic is carried away.
If You Get an Ice Dam
- If your roof is still under workmanship warranty, we recommend hiring the roofing contractor that installed your shingles to get rid of the ice dam for you. You do not want to void your warranty by chipping away ice and damaging shingles. If you do have to chip the ice away, do not use an axe or hammer (or anything that may damage the shingles), use a blunt mallet and tap lightly. This is a very slow and dangerous process, so take extreme care.
- You can also use a melting agent like calcium chloride which you can get at your local hardware store. Do NOT use rock salt, this can damage paint, drain pipes and plants that will access the melted salty water.
- Clear out your gutters and downspouts. You may want to consider installing a continuous hanger system to help with the clogging of ice and snow.
- Helpful Hint: To make a pathway for the water to drain, take a leg from an old pair of panty hose, fill with calcium chloride (again NOT rock salt), tie it off and lay it vertically across the ice dam. This will slowly melt its way through the ice dam, clearing a path for the melted water underneath.
Common Ice Dam Locations
Please see the diagram below to explain the most common ice damming locations on a home as illustrated by The Ice Dam Company.