An ice dam is a ridge of ice that forms at the cold edge of a roof and traps meltwater behind it. The water backs up under the shingles, then drips into the attic, down the inside of exterior walls and onto the ceiling below.
How the water gets in
Heat escaping from the living space warms the roof deck, snow on the upper roof melts, and the runoff refreezes where the eave stays cold. Minnesota winters offer that cycle plenty of chances, and a damp ceiling edge or a stained corner is usually the first sign that it has started.
- Wet or compressed insulation in the attic
- Stains at the top of exterior walls
- Drips at ceiling lights or bath fans
- Peeling paint along the edge of a ceiling
What the crew removes
Wet insulation is pulled out first, because it holds water against the ceiling drywall and the framing. Sagging drywall is cut down, and the tops of exterior walls are opened if the meter shows water running inside the cavity. Ceiling light fixtures that took water are shut off until an electrician has looked at them.
Drying, then fixing the cause
Dehumidifiers and air movers dry the attic floor, the ceiling joists and the opened walls together. The roof edge, ventilation and insulation need a separate repair, and a stain that spread low in the house may overlap with a ceiling leak or with structural drying.