Ice Dams & Roof Snow Removal

An ice dam is a ridge of ice that forms at the edge of a roof and stops melting snow from draining. Water backs up under the shingles and leaks into the attic, walls and ceilings. Removing snow and ice from a roof is also dangerous. People fall from ladders and roofs, get hit by falling ice, and touch power lines. The best fix is to prevent ice dams from forming.

• Homeowners
• Landlords
• Winter Safety

How ice dams form

1. Heat from the house leaks into the attic and warms the roof deck.
2. Snow on the warm part of the roof melts, and the water runs down.
3. At the colder eaves, which are over the unheated overhang, the water refreezes and builds up a ridge of ice.
4. More melting water backs up behind the dam and gets under shingles, through nail holes and into the house.

Ice dams need snow on the roof, a warm roof surface and cold at the eaves. They are more common on roofs with poor insulation and air leaks, and on complex roofs with valleys and dormers.

Damage ice dams cause

• Water leaks into ceilings, walls and insulation, with stains, peeling paint and sagging drywall.
• Mold and rot in the attic and walls. See Home Mold.
• Wet insulation that loses its insulating value.
• Damaged gutters and shingles, and falling icicles that can seriously injure people.
• Heavy snow loads and ice can also stress a roof, and in the worst cases can cause collapse, especially on flat or weak roofs.

Prevention: fix the root cause

• Seal air leaks from the house into the attic. Look around attic hatches, recessed lights, pipes, wires, chimneys and bath fans. Warm moist air leaking into the attic is the biggest cause. Use caulk, foam and weatherstripping, and seal around chimneys with fire-rated materials. Don’t block vents or cover heat-producing fixtures that aren’t rated for insulation contact.
• Add insulation to the attic floor to keep heat in the house, to the levels recommended for your region, while keeping air space for ventilation.
• Ventilate the attic with soffit vents at the eaves and ridge or gable vents higher, so cold air flows under the roof deck and keeps it cold. Use baffles to keep insulation from blocking soffit vents.
• Vent bath fans, dryers and range hoods outdoors, not into the attic.
• Consider an ice and water shield membrane under the shingles along the eaves when replacing the roof, a roofing professional can install it.
• Keep gutters clear so that water can drain. See Winter Storms.
• Hire an energy auditor or a qualified contractor to check insulation and air sealing. Permanent fixes are better than temporary removal. See Hiring Contractors.

Removing snow from the roof safely

• Stay on the ground. Use a roof rake with a long handle to pull snow off the lower few feet of the roof from the ground, taking care to avoid damaging shingles. Start at the edge and work up.
• Use a non-metal (plastic, wood or fiberglass) roof rake, never a metal one, to stay safe from power lines. Look up for overhead service lines, and stay far away from them. See Overhead Power Lines.
• Wear a hard hat and eye protection, and stay out from under the snow and ice you’re pulling. Large slabs of snow can slide down suddenly. Don’t stand below the eaves. See Hard Hats.
• Keep your footing: clear the area of ice, wear boots with good traction and have someone watch. See Slips, Trips & Falls.
• Take it slowly. Shoveling and raking snow is hard work that can bring on heart attacks. If you have heart trouble, don’t do it. Take breaks, and dress warmly. See Cold Stress.
• Remove snow gradually, leaving a thin layer on the shingles to avoid damage.

• Don’t climb onto a snowy or icy roof, or use a ladder on icy ground. Roofs are extremely slippery under snow. See Ladder Safety at Home and Roof Work.
• Don’t use an axe, hammer, chisel, pick or shovel to chip ice off the roof. This damages shingles, gutters and flashing and creates leaks, and injures people.
• Don’t use a torch, open flame or heat gun, which can start a fire. See Heat Guns.
• Don’t pour hot water on the roof, which can refreeze and damage the roof.
• Don’t use a pressure washer or a salt-based product that can harm shingles, metal and plants.

Dealing with an existing ice dam

• If water is leaking in, protect belongings, catch drips and poke small drain holes in bulging ceiling drywall to release trapped water, if safe (turn off the power if wiring is wet). Then call a professional.
• Calcium chloride (not rock salt) ice melt in a tube, such as a sock or nylon stocking, placed across the dam, can melt a channel for the water to drain. Place it from the ground with a rake, don’t climb. It may damage shingles and plants, so use sparingly.
• Professionals use low-pressure steam to remove ice dams without damaging the roof. This is usually the best choice for large dams. Make sure the contractor is insured and trained in roof safety.
• Heat cables (heating cables installed along the eaves) can keep a channel open, but they are a Band-Aid, use electricity and can cause fires if installed poorly. Have them installed by a qualified person, plugged into a GFCI outlet. See Home Electrical Safety.
• Fix the cause (air leaks, insulation and ventilation) once the weather permits.

Falling ice and icicles

• Icicles and ice slabs can fall without warning and cause serious injuries. Keep people, pets and cars away from the edges of roofs, and mark walkways under heavy ice. See Fall Prevention at Home.
• Knock down icicles from the ground only with a safe tool, standing clear, and wearing eye protection and a hard hat.
• Landlords and building owners should keep entrances safe. See Landlord Safety Duties.

Heavy snow loads and roof collapse

• Heavy, wet snow and rain on snow can overload a roof. Warning signs: sagging ceilings, new cracks in drywall or plaster, doors and windows that stick, creaking and popping sounds, bowed ceiling or roof lines, and leaks.
• If you see warning signs, leave the building and call 911 or a structural engineer. Don’t go back in.
• Flat roofs, large low-slope roofs and outbuildings are most at risk. Have a professional remove snow from large or flat roofs, with fall protection and the right equipment.
• Know your local snow load rating and check roof condition before winter.

Ice dam and roof snow checklist

• Attic air leaks sealed; attic floor insulated; attic vented at the soffits and ridge
• Bath fans, dryers and range hoods vent outdoors
• I clear snow only from the ground, using a non-metal roof rake, away from power lines
• I wear a hard hat and eye protection and never stand under the snow I pull
• I don’t chip ice, use torches or climb onto a snowy roof
• I call a professional for large ice dams, flat roofs and any sign of roof overload

Last updated: October 4, 2026