Ice Dams and leaking roofs in the winter
Since it is snowing here in Cincinnati, I thought I?d write a quick article on Ice dams and the possibility of leaking roofs. Ice dams form when the snow melts either from the top of the roof (from the sunshine), or warm air from the house enters the attic and melts the snow from the underside of the roof decking. When the water runs down the roof like it should, it can re-freeze along the way, and build up as a dam that traps the water and prevents from going down the shingles (or slate or wood shakes) to the gutters and down and away from the home. This ice buildup creates a pool and causes the water to go back up the roof shingles, where it easily gets under the roof material and hits the sheathing, and potential leaks into the living area of the home. There isn?t anything you can do about the temperature, or even from keeping the ice from forming.
There are a few things you can do to at least minimize the possibility of ice dams.
First is to ensure good ventilation in the attic, so there is not a dramatic difference in temperature between the outside air and inside the attic. Roof or gable vents near the peak of the roof are good starts. Soffit and ridge vents are better. (Soffit vents are at the lowest section of the roof near the gutters, and ridge vents run along the peak of the roof.) This allows the cool air to enter the lower portion of the attic, and flow upper wards toward the ridge vents and exit as hot air. This prevents heat from building up in the attic, even in the winter time, and causing snow to melt at the top of the roof, and re-freezing near the bottom.
Good insulation in the attic keeps the warm air inside the home, not quickly rising upward and exiting the attic. Caulk around attic openings or install a nice Styrofoam or Batt insulation piece directly above opening (in the attic) to prevent heat loss in this vulnerable area.
There are also some products available that can be applied to the most vulnerable areas of the roof; valleys, slope changes, eaves, along with the rake boards. These products are installed not to prevent the ice from damming, but to prevent the water from penetrating the roof decking once the dams have formed. Calling a qualified roof contractor to discuss your options is a good idea.
Nobody wants their roof to leak at any time, but hopefully understanding the phenomenon of ice dams can take the anxiety out of a simple leak. Keep you from thinking you have to replace the entire roof and give you a couple of tricks to defend your home from unwanted water entry.