Ice Dams: Prevention, Removal, and Roof Damage

Q: What causes ice dams on roofs?

Ice dams form when heat escapes from the living space into the attic, warming the upper portion of the roof and melting snow there. The meltwater flows down to the colder eaves, where it refreezes and forms a dam. Water backs up behind the dam and can seep under shingles, damaging decking, insulation, and ceilings below. The root cause is insufficient attic insulation and inadequate ventilation.

Q: How do I safely remove an ice dam?

The safest removal method is calcium chloride ice melt applied in a nylon stocking laid perpendicular to the dam across the eave. Do not use rock salt, which damages shingles and plants. Do not chip or chop at ice dams with sharp tools, which risks damaging the roof surface. Roof rakes can safely remove snow from the ground before it creates new ice dams.

Q: Does homeowners insurance cover ice dam damage?

Ice dam damage is typically covered under standard homeowners insurance as a sudden and accidental loss. However, damage that results from repeated, unaddressed ice dams may be denied as a maintenance issue. Document the damage immediately and file promptly. The ice dam itself is not covered, but the interior water damage it causes usually is.

What Causes Ice Dams

Ice dams are a symptom of a heat transfer problem, not a weather problem. Here is how they form:

Heat escapes from the conditioned living space into the attic through inadequate insulation or air sealing
The warm attic heats the roof deck, melting snow on the upper portion of the roof
Meltwater flows down toward the eaves, which remain at outdoor temperature since no heat escapes there
The water refreezes at the eave, forming an ice dam that grows with each melt-freeze cycle
Water ponds behind the dam and backs up under shingles, entering through gaps in the starter course

The Damage Ice Dams Cause

Ice dams can cause extensive damage throughout the home:

Shingle damage: Water backing up under shingles lifts them and degrades the sealing strip, shortening lifespan
Decking rot: Prolonged water intrusion saturates the OSB or plywood decking, causing rot and structural weakness
Insulation damage: Wet attic insulation loses most of its R-value and can develop mold
Ceiling and wall damage: Water that penetrates to the living space stains and damages drywall, plaster, and paint
Mold: Any sustained moisture in attic spaces creates conditions for mold growth

Safe Ice Dam Removal

What Works

Calcium chloride: Fill a nylon stocking with calcium chloride ice melt. Lay it perpendicular to the dam extending over the eave. It creates a channel for meltwater to drain through. Works slowly but safely.
Roof rake: A long-handled roof rake can remove snow from the ground before it contributes to new ice dam formation. Remove snow from the lower 3-4 feet of roof.
Professional steam removal: Ice dam removal contractors use low-pressure steam to safely melt dams without damaging shingles. More expensive but the safest and most effective option for severe dams.

What Not to Do

Do not use rock salt — it corrodes metal gutters, kills plants below, and damages shingles
Do not chip or chip at ice with an axe or chisel — risk of shingle damage and personal injury on an icy roof is high
Do not use heat cables as a primary ice dam solution — they address symptoms but not the underlying cause

Preventing Ice Dams: The Right Fixes

Ice dam prevention addresses the root cause: heat escaping from the living space into the attic.

Air sealing: Seal all penetrations between the living space and attic — recessed light fixtures, plumbing chases, top plates, attic hatches. Air sealing is more impactful than adding insulation alone.
Insulation upgrade: Cold climate building codes typically require R-49 to R-60 in the attic. Many older homes have R-19 or less. Adding blown-in insulation over existing insulation is the most common fix.
Ventilation improvement: Adequate soffit and ridge ventilation keeps the roof deck cold and uniform, preventing the warm-upper/cold-lower pattern that causes dams. See: Signs of Poor Roof Ventilation
Ice and water shield: During reroof, installing a membrane underlayment (ice and water shield) from the eave up to 24 inches past the interior wall provides a backup barrier against water intrusion

Frequently Asked Questions

What causes ice dams on roofs?

Heat escaping from the living space into the attic warms the upper roof, melting snow. The meltwater refreezes at the cold eaves, creating a dam. The root cause is inadequate attic insulation and air sealing.

How do I safely remove an ice dam?

Calcium chloride in nylon stockings laid perpendicular to the dam creates drainage channels. Professional steam removal is the safest option for severe dams. Do not use rock salt or chip at ice with sharp tools.

Does homeowners insurance cover ice dam damage?

Typically yes for sudden water intrusion damage to ceilings and walls. Repeated ice dam damage may be denied as a maintenance issue. Document and file promptly after discovering damage.

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This page is for general informational purposes only. Do not access a snow-covered or icy roof without proper safety equipment and training. Consult a licensed roofing contractor for an assessment of ice dam damage and recommended fixes.