Ice dams can form on the overhangs of pitched roofs. This happens in areas with prolonged periods of freezing weather. Heat loss from the homes interior and solar heat from the sun can cause the snow on the roof to melt. As the water reaches the cooler area of the overhang, it starts to freeze near the edge of the roof and forms an ice dam. If the ice dam gets big enough it starts to trap water from the the melted snow. As the water pools behind the ice dam it backs up under the shingles and enters the buildings interior.
To help prevent ice dams form forming there are several thing that you can do to help. First make sure your attic is insulated properly for the climate you live in. Make sure that your attic access fits properly and is insulated. Make sure you are not losing heat through
your recessed lighting. Don’t run your bathroom and kitchen vents into the attic, they should be direct vented to the outside of your home. Your attic should be well ventilated to remove any heat and moisture out of the attic space. Seal all penetrations that pass into the attic. Finally, if the duct work is in the attic space, it should be sealed and insulated to prevent heat loss into the attic. Taking these steps will prevent ice dams form forming on your roof.