One of the most common cause of winter ice and water damage is Ice Dams.
An ice dam is a problem of house and building maintenance in cold climates. It can occur when snow accumulates on the slanted roof of a house with inadequate insulation. In these cases, heat then melts snow on the roof but will not touch that which extends onto the overhangs. Eventually, ice accumulates along the eaves and gutters preventing melting snow to drain properly. This leads to leaks and structural damage to the roof, insulation, ceilings and walls.

 
Preventing Ice Dams

Ice dams can be prevented with a bit of attention to your roof. The most critical method is through proper insulation. Using the appropriate type and amount of insulation in your attic and ceiling can help prevent heat escape that causes ice dams. Some suggest the use of a dehumidifier in your attic to eliminate water vapor that can also create an ice dam. Furthermore, sealing any openings in the home such as ceiling mounted fixtures, ceiling fans and junction boxes will also prevent water vapor penetration into the attic and onto the roof.

Other ways to prevent ice dams include 1) keeping your attic air temperature below freezing, especially when the outside air is also below freezing; 2) keeping your gutters and downspouts free of leaves and other debris; 3) raking out fresh snowfall from gutters; and 4) wrapping or insulating all heating ductwork in your home.