How to Prevent Ice Dams on Your Roof

What an ice dam is

An ice dam is a ridge of ice along the edge of your roof. Snow higher up melts, runs down to the colder eaves and refreezes. Each melt-freeze cycle makes the ridge bigger, until meltwater pools behind it and works its way under the shingles and into the house.

Why they form

The cause is almost always heat escaping from the living space into the attic: gaps around light fixtures and chimneys, thin insulation, and poor attic ventilation. A warm roof deck melts snow even when it's well below freezing outside, while the overhang past the walls stays cold.

How to prevent ice dams

If an ice dam is already forming

• Don't chip at it with a hammer, axe or shovel. It breaks shingles and bends gutters.
• Don't climb an icy roof or ladder.
• Be careful with salt products, which can harm plantings, metal and finishes.
• Watch ceilings and walls below for stains, and photograph any damage for your insurance company.
• Call for ice dam removal. We carefully cut channels through the ice by hand so the water can drain, without damaging the roof.