hellziggy

Here's how ice dams work: Roofs are warmer than the rest of the outside of your house because you lose heat through the roof. So the snow melts and runs down the slope of the roof until it reaches the edge. Then there's nothing to really keep it warm anymore, so it freezes and fills the gutters. And then the water behind it keeps rolling down, and it freezes too. This keeps happening until the frozen ice on the edges of the roof gets too high for the water behind it to trickle over, so the water has nowhere to go. It just backs up on the roof behind the ice dam and sits there and can't melt because of the escaped heat from the house. Standing water on roofs is not good -- it gets under the shingles and comes into the house walls and leaks in, usually around the doors and windows. We've had a great setup this winter for them -- heavy snow, followed by a series of thaws and freezes.

Things to fix the ice dam include, for now, getting the snow off your roof so the stuff right next to the shingles can freeze, and clearing the gutters of ice. This summer you will probably have to track down the roof damage and fix it.

For long term, the most effective way to prevent them is pretty easy -- more insulation in the attic. This will prevent heat loss, and have the added benefit of lowering your heating bills and making the house more comfortable.