What Is Ice Dam Formation and How Does It Cause Roof Leaks?

Ice dams happen when heat from your attic warms the roof, melting snow from the top down. The meltwater runs toward the eaves, where the roof is colder because it extends past the heated space. That cold edge refreezes the water into a ridge of ice, which is the dam.

As more snow melts, water pools behind the dam. The pooled water can back up under the roof shingles and find its way into the roof deck. Over time, this causes leaks inside your home, often at the walls or ceiling. The process is slow, so you might not notice until the damage is visible.

You might notice icicles hanging from your gutters, which often indicate a dam is forming. Also look for water stains on interior ceilings or walls, especially near exterior walls. A damp attic or frost buildup on the underside of the roof deck can signal poor ventilation.

Another sign is ice buildup along the edge of the roof, even when the rest of the roof is clear. If you see these signs, you should act quickly to remove the dam safely. Never try to chip ice off the roof while standing on a ladder in winter; that is dangerous.

If water is already leaking into your home, start by containing the drip with a bucket and move furniture out of the way. Then dry the area as much as possible with towels and fans. You can also remove wet insulation or drywall to prevent mold growth.

Once the immediate mess is under control, you need to address the roof leak source. That may involve removing the ice dam or repairing the roof. After the roof is fixed, you might need to repair the water-damaged drywall and insulation. Local water damage pros can handle the cleanup and restoration work.