Ice Dam Leaking Into Your House? What to Do

An ice dam forms when heat escaping into the attic warms the roof deck and melts the underside of the snow. The meltwater runs down to the colder eaves, which sit beyond the heated part of the house, and refreezes into a ridge of ice. More meltwater pools behind that ridge, works its way under the shingles, and drips into the attic, the top of exterior walls, or the ceiling. Long icicles along the gutters are often a visible clue.

Inside: deal with the leak first

• Catch the water with buckets and towels, and move furniture and electronics away.
• Watch for electrical hazards. If water is coming through a light fixture or near outlets, switch that circuit off at the breaker panel from a dry spot.
• Stay out from under sagging drywall. If a section of ceiling has filled with water and there is no wiring nearby, a small controlled hole at the low point with a bucket below can keep it from collapsing. See our first 60 minutes guide.
• Check the attic if you can do it safely. Wet insulation and damp roof sheathing show how far the water spread. Put a pan or tarp under active drips.
• Photograph the ice dam from the ground, the interior leak, and any attic damage for your insurer.

Outside: what’s safe (and what isn’t)

Don’t climb onto an icy roof, and don’t lean a ladder against icy gutters. Falls from roofs and ladders are a real winter risk.

Don’t chop at the ice with a hammer, hatchet, or shovel. It is easy to break shingles and gutters, which turns a temporary leak into a roof repair.

Safer options:

• Roof rake from the ground. Pulling the first few feet of snow off the roof above the eaves removes the supply of meltwater. Use a rake designed for roofs, work from the ground, and stay clear of power lines.
• Calcium chloride (not rock salt). A common approach is to fill a nylon stocking with calcium chloride ice melt and lay it vertically across the dam so it melts a drainage channel. Rock salt (sodium chloride) can damage roofing, gutters, and plants below.
• Professional ice dam removal. Many roofing contractors use low-pressure steam to cut channels through the ice without damaging shingles. Avoid pressure washers and open flame.

After the leak stops

Water from an ice dam often soaks attic insulation and the top of wall cavities, where it can stay wet long after the weather turns. Wet insulation loses much of its value and can lead to mold. A restoration contractor can measure moisture in ceilings and walls and dry or remove wet materials. A roofer can check shingles, underlayment, flashing, and gutters for damage.

Preventing ice dams

The long-term fix is a colder roof deck: seal attic air leaks (around light fixtures, bath fans, attic hatches, and chimneys), add attic insulation where it is thin, and make sure soffit and roof vents move air. When a roof is replaced, an ice-and-water barrier membrane along the eaves helps keep meltwater out. Heat cables along eaves can help in problem spots but are a supplement, not a cure.

Insurance

Many homeowners policies cover interior damage caused by ice dams, while repairing the roof for wear or maintaining it to prevent dams is on the owner. Document the dam and the damage, and ask your adjuster how your policy treats it.

Frequently asked questions