Ice Dam on Your Roof? What to Do Now, What Not to Do, and How to Stop the Next One

Icicles along the gutters, a ridge of ice at the edge of the roof, and a day or two later, a brown stain on the ceiling near an outside wall. That is an ice dam: ice at the cold eaves holding back meltwater that has nowhere to go but under the shingles. You can't fix it from the roof in midwinter, and the usual attempts, with a ladder, a hammer, or a torch, often do more harm than the dam does.

Below: what the signs mean, what to do if water is coming in, how to relieve a dam from the ground, when to call a roofer, and how to fix the cause, which is almost always heat escaping into the attic. It builds on the ice dam section of our winter guide.

What You're Seeing

Heat leaking from the house warms the roof deck and melts the snow above the living space. The water runs down to the cold eaves and freezes into a ridge that grows with every melt; water pools behind it and leaks through the roof into the attic, walls, and ceiling (University of Minnesota Extension). The Building America Solution Center, a Department of Energy program, says a dam can form under as little as 2 inches of snow.

• Icicles and a ridge of ice at the eaves. The Solution Center says icicles are often a sign that more water is building up behind a dam. Bare patches higher up on a snowy roof show where heat is escaping.
• Stains or drips inside, on the ceiling or high on an outside wall, or below a skylight, during or after snow and freezing weather. Peeling paint can appear long after the ice is gone (UMass Amherst).
• Wet, flattened, or frosty attic insulation. Wet insulation has little insulating value (Minnesota Department of Commerce), and frosty or dust-darkened patches mark where warm air is leaking in (ENERGY STAR).

If Water Is Coming In Right Now

1. Keep water and electricity apart. The Red Cross and Ready.gov say not to touch electrical equipment that is wet or while you're standing in water. If water is near a ceiling light, fan, or outlet, leave it and its switch alone. Turn off that circuit at the panel only if you can reach it standing on a dry floor with dry hands; otherwise call an electrician. Have anything that got wet checked before the power goes back on.
2. Move belongings and catch the water. Get furniture, electronics, and rugs out of the drip path, lay down plastic or towels, and set buckets under drips. A wet/dry vac picks up standing water.
3. Photograph everything before you clean up. The National Association of Insurance Commissioners (NAIC) advises photos or video, a list of the damage, temporary repairs to prevent more, every receipt, and a prompt call to your insurer, since most have reporting deadlines.
4. Check the attic, if you can do it safely. With a flashlight, step only on the joists, never the drywall between them, or you can fall through the ceiling (ENERGY STAR). Look for wet insulation, frost, and water on the underside of the roof deck. ENERGY STAR says wet insulation calls for a professional.
5. Dry it out within 24 to 48 hours, the EPA's window for preventing mold, with fans and a dehumidifier; large soaked areas need a water-removal company. Don't repair ceilings and walls until they're dry, and fix the heat loss at the same time, or the damage will recur (Extension).

What You Can Do Safely From the Ground

You can't safely remove the ice, but you can remove what feeds it. Rake the snow off the lower 3 to 4 feet of roof above the eaves, standing on the ground, after every heavy snowfall. Stop at the ice, and leave a thin layer of snow instead of scraping the shingles; the Extension warns that roof rakes can damage roofing, and the makers say their rakes are for snow, not ice. Rakes suit one-story eaves; a second story is a roofer's job. Our roof rake guide compares them.

• Use a non-metallic rake. FEMA says metal snow rakes can damage roofing and pose an electrocution risk, and should be avoided.
• Look up before you raise the pole. Even a fiberglass pole is no reason to get closer: OSHA says to keep at least 10 feet between any power line and you, the pole, and the rake, and to treat every line as energized, including the service line to your house. If you can't keep that distance, leave that stretch to a roofer.
• Stay out of the fall zone. OSHA warns that snow sliding off a roof can bury and suffocate someone below. Pull small amounts, don't stand under the eave, keep people and pets 10 feet back from where the snow lands, and wear eye and head protection; even a short-falling icicle can injure (FEMA).
• Never rake from a ladder. OSHA says it greatly increases the risk of losing your balance and falling.
• Pace yourself. Ready.gov warns that overexertion shoveling snow raises heart attack risk; raking is similar work, so take breaks.

What Not to Do

• Don't climb onto the roof. OSHA finds that falls cause the most deaths and injuries in rooftop snow removal.
• Don't chip, hammer, or pry at the ice. It damages shingles and flashing, and IKO, a shingle maker, notes that the cracks give the next dam a way in.
• No torches, heat guns, or open flame. The Minnesota Department of Commerce warns that removing ice with heat can damage shingles and gutters, and flame at the roof edge is a fire risk.
• No pressure washer. IKO says not to use one on a roof; the spray can lift and damage shingles.
• No rock salt or chemical tricks. Rock salt corrodes gutters and damages shingles, the Minnesota Department of Commerce warns that chemicals can damage shingles and gutters, and IKO says ice-melt tablets may void the shingle warranty. That includes the calcium chloride-in-a-stocking trick; none of the official sources we checked recommends it.

When to Call a Pro

Call a roofer when a dam is leaking, large, above the first story, or near the service line. The Extension's emergency measure is a channel through the dam so trapped water can drain. It describes cutting one with tap water on a warm day, notes that the channel stops working within days, and warns that anyone working on the roof in winter, even from below, risks injury and damage, so professionals should do it. Ask how they will remove the ice, and turn down anyone who plans to chip or pressure-wash it.

Call an electrician if water reached a fixture or wiring, a building official or structural engineer for a sagging ceiling, and a water-removal company for soaked drywall or insulation. After winter, hire a weatherization contractor who runs a blower door test to find the air leaks (Extension).

Most Likely Causes

Ice dams are a heat-loss problem. These are the usual reasons, most common first.

1. Warm air leaking into the attic. The Extension calls air leakage the major cause in many homes. The gaps hide under the insulation: around wiring, recessed lights, plumbing stacks, flues, the attic hatch, and exhaust fans (Solution Center).
2. Thin insulation above the outside walls. Where the rafters rest on the walls there is little room for insulation, so the roof just above runs warm (UMass Amherst). Insulation flattened by an earlier leak insulates less, too.
3. Heat sources in the attic. Leaky or poorly insulated ducts, a chimney warmed by frequent fires, and exhaust fans that end just above the roof all add heat (Extension).
4. Blocked soffit vents. Baffles should keep insulation out of the soffit vents so cold air can flow under the roof deck (Solution Center). Vents help but don't cure: the Minnesota Department of Commerce says adding roof vents, powered ones included, won't eliminate ice dams and often makes them worse.
5. The shape of the house. Skylights and complex roofs raise the risk (Extension), story-and-a-half homes often can't hold enough insulation (Center for Energy and Environment), and a higher roof draining onto a lower one is prone to dams (IKO).
6. Deep snow. In an unusually snowy winter, snow can insulate the roof enough to cause dams even on a well-insulated house (Center for Energy and Environment).

Gutters are rarely the cause, though a gutter full of ice can bend and pull away from the house (IKO, UMass Amherst).

Prevent It

The fix is a cold roof deck, and our fall checklist schedules it before the snow. In this order:

1. Air-seal the attic floor first. The Solution Center calls it the most important step, and ENERGY STAR and the Extension both put insulation after it. Start with the hatch: ENERGY STAR says to weatherstrip it and fasten insulation to its back, and our weatherstripping guide covers the materials.
2. Insulate to the level recommended for your climate zone.
3. Keep soffit and ridge vents clear, and send every exhaust fan and dryer vent outdoors, not into the attic.

ENERGY STAR calls attic air sealing a difficult DIY project and recommends a professional if you find wet insulation, mold or rot, or knob-and-tube wiring; don't disturb vermiculite insulation until a lab confirms it has no asbestos. A tighter house can also let carbon monoxide build up if fuel-burning appliances don't vent properly, so ENERGY STAR says to have a heating technician check them afterward.

Heat cables are a partial measure at best. RAYCHEM says its WinterGard Wet cable provides a drain path for meltwater, not snow clearing. A cable does nothing about the heat loss, and the Minnesota Department of Commerce says heating cables shorten roof life and cost money to run. If you use one, have it installed before winter exactly as the maker specifies; RAYCHEM requires ground-fault protection and warns that incorrect installation can cause shock or fire.

Clean the gutters before the first snow (our ground-level gutter guide shows how), and when the roof is replaced, ask for self-adhered membrane along the eaves, which codes often require (Solution Center).

Frequently Asked Questions

Do icicles mean I have an ice dam?

Not always, but the Building America Solution Center says icicles are often a sign that water is building up behind a dam. A thick band of ice along the roof edge with icicles hanging from it is the pattern to watch. Keep people out from under large icicles.

Can I put ice melt or calcium chloride on the roof?

The sources we checked advise against it. The Minnesota Department of Commerce warns that chemicals can damage shingles and gutters, IKO says ice-melt tablets aren't recommended for asphalt shingles, and rock salt corrodes gutters. Any melting product treats the symptom, not the heat loss, and getting it onto the dam means a ladder or the roof. Rake the snow from the ground and call a roofer for the ice.

Does homeowners insurance cover ice dam damage?

Often, but coverage varies. Allstate, for example, says dwelling coverage may help pay for ice dam water damage, but a policy likely won't pay to remove the dam, and personal property coverage typically doesn't cover belongings it damages. Read your policy, document the damage, and call your insurer promptly.

The Bottom Line

Protect the room first: stay out from under a sagging ceiling, keep away from wet fixtures, move belongings, catch the drips, and take photos. Then rake the lower 3 to 4 feet of roof from the ground, 10 feet from any power line, and leave the ice to a roofer: no ladders, hammers, flames, pressure washers, or salt. Afterward, air-seal the attic, then insulate. The rake treats the symptom; the attic work is the cure.

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