Ice damming is caused by clogged gutters and or leaders.. A well designed roof will have a metal ice shield under the shingle extending back at least one foot from the roof edge. Simply cleaning the gutters will keep the water flowing when the snow on the roof gets melted from the heat of your home. Its just that simple. Clean your gutters two to three times a year. Especially after the fall.
charles
A clogged gutter can cause a ice dam, but most ice dams are caused by improper construction. Not enough attic ventilation and not enough insulation in the ceiling (assuming a unconditioned attic) is the main cause of ice dams. Snow on the upper portion of the roof melts, flows down towards the overhang and then freezes because that area isn't heated by escaping attic heat. Ice dams occur when the outside temps are in the 15-25 degree F range. Colder than that the roof is cold enough the snow doesn't melt and warmer than that the overhang area is warm enough so no freezing occurs.
You can shovel the snow to reduce ice dams but if you do don't use a metal shovel/rake. They're very rough on the protective coating on the shingles. You can remove ice dams with a pressure washer but if you don't know what you're doing it'll also ruin your roof and maybe a bunch of drywall.
If you have ice&water shield you can still have extensive damage. Water will find a way through any gap. There are no gaps with Ice&water shield
if it is installed perfectly, but the constant freeze/thaw of ice dams will eventually make an opening.
Essentially an ice dam is nature telling you that your home has a defect that will eventually cost you big bucks if you don't fix it.
