Solved! How to Prevent and Remove Ice Dams
If your roof is weighed down by heavy icicles every winter, you may have an ice dam problem. Follow these techniques for removing ice dams before they damage your home—or hurt someone.
Q: After a recent snowstorm, a large band of ice formed above the edge of my roof and created some heavy icicles as well. The weight of the ice is starting to pull the gutter loose, and I’m afraid it will pull it off entirely. Is there anything I can do to get rid of the ice before it tears up the gutter or falls on someone?
A: What you’re describing is an ice dam, and, unfortunately, it’s very common on homes in areas that experience cold and snowy winters. An ice dam results from snow that melts and then refreezes—known as a freeze/thaw cycle—and the culprit is an abnormally warm roof.
When the air inside an attic is warm, that warmth can transfer through the roof and begin to melt the layer of snow, which in turn causes droplets to run down the roof. When those droplets reach the edge of the roof, they refreeze because the part of the roof above the overhang (the eaves) doesn’t receive warm air from the attic.
As additional snow melts, runs down, and refreezes, the layer of ice continues to build, creating a literal dam—a barrier that prevents water from running off the roof. Ice dams, and the inevitable icicles that result from them, might make your home look like a gingerbread house, but be warned: They are a hazard to your home and family.
Dangers of Ice Dams
As ice dams build, they get heavier. When the weather warms enough for the ice to melt, the dam can loosen enough to come crashing to the ground—sometimes taking the home’s gutter with it. Ice dams can harm the roof in other ways as well. As water seeps between shingles and freezes, it expands, loosening the shingles and penetrating through the layers of the roof until you have a leak and interior water damage.
Since you’re dealing with one (or more) already, we’ll share some of the best techniques for removing ice dams. But keep this in mind for future winters: The key to long-term protection lies in preventing ice dams before they occur.
Ice Dam Removal
Once an ice dam forms, it’s essential to remove it before further thawing and freezing cause it to expand and put the roof and gutter at additional risk. The most common ways of getting rid of ice dams include treating the ice with a chemical that will cause it to melt or using ice dam tools to break the ice into small chunks for removal.
Melt the ice dam with calcium chloride. Calcium chloride, such as Morton’s Safe*T*Power, is the same stuff used for melting ice on driveways and sidewalks, but don’t just sprinkle it on the ice dam. Instead, fill tube socks or pantyhose legs with the granules and then tie off their ends with string.
A 50-pound bag of calcium chloride costs around $20 and will fill approximately 13 to 15 tube socks. By using calcium chloride in this way, you can position each sock vertically over the dam—with the sock’s end hanging an inch or two over the roof edge. As it melts the ice, it will create a tube-like channel through the ice dam, which will allow additional water that melts to run safely off the roof.
A word of caution: Do not substitute rock salt for calcium chloride when trying to melt an ice dam, as sprinkling rock salt on roofs can damage shingles, and the runoff can kill bushes and foliage beneath. Make sure the ice-melt product you buy contains only calcium chloride, which is safe for shingles and vegetation.
Break existing ice dams into chunks. Breaking an ice dam can be dangerous and, if you’re not extremely comfortable being on a snowy and icy roof, is better left to the professionals. Breaking an ice dam is usually done in conjunction with melting the ice in some fashion, such as using calcium chloride socks as described above or with roof steaming (see below).
First, a cautious homeowner or professional hire should clear the roof of excess snow and melt drainage channels in the dam. Then, as the ice is beginning to melt, the edges of the channels can be carefully chipped away with a mallet, such as TEKTON’s 16-ounce fiberglass mallet, to widen them and hasten drainage. Never use an ax or hatchet to chop the ice, which can cause damage to the roof.
Breaking an ice dam can result in large swaths of ice crashing off the roof, breaking windows, damaging bushes, and injuring anyone below, so extreme caution must be taken. The person breaking the ice dam should do so from a vantage point on the roof, not from the ground where the heavy ice sheets can fall.
Hire a roofing professional. Steaming away ice dams is a professional-only task because it requires commercial steaming equipment that heats water and dispenses it under pressure. The roofing professional will first remove excess snow from the roof by shoveling and then steam channels through the ice dam to help it melt. The worker may also chip away parts of the dam until the roof is clear of ice. Hiring a professional ice-dam removal crew is pricey, and may run you $200 to $300 per hour.
Ice Dam Prevention
Cold weather can wreak havoc on houses. Some ice dam prevention methods require removing snow from your roof, while others entail lowering your home’s attic temperature to prevent heat transfer from the attic to the roof. Try one or more of the following methods of ice dam prevention.
Rake the lower 3 to 4 feet of the roof after a snowfall. This is best done with a lightweight roof rake such as the Snow Joe Roof Rake, which comes with a 21-foot extension. Immediately after a snow, when the snow is still soft, rake the roof’s eaves clear of snow. This will help reduce ice buildup. The best roof rakes will last for years and make rooftop snow removal a snap because climbing a ladder isn’t necessary.
Add attic insulation. The idea is to stop the transfer of heat through the roof, which triggers the freeze/thaw cycle. An extra 8- to 10-inch layer of attic insulation will help prevent heat transfer and help retain heat inside your home, so you’ll spend less to keep your house warm in the winter. A quality attic insulation, such as Owens Corning’s R-30 Insulation, will keep heat from the living space from seeping into the attic, and in doing so, will also reduce the risk of ice dam formation.
Seal all interior airflow leaks in the attic. No matter how much insulation you add to your attic, if warm air from the living space flows through gaps and vents, the attic will still be too warm. Eliminating interior airflow involves sealing all gaps around sewer vent pipes with expanding foam and having bathroom and dryer vents rerouted from the attic through an exterior wall of your home. A quality insulating foam, such as Great Stuff Gaps & Cracks, will block hot air from flowing from the living space into the attic.
Ventilate your attic to keep it cool. Intake attic vents should be installed along the underside of the roof eaves in the soffit, and exhaust vents should be located near the top of the roof. Cool air will naturally enter a soffit vent, such as the HG POWER Soffit Vent. As the cool air warms in the attic, it rises and exits through an exhaust vent, such as the Master Flow solar power roof vent, which should be located near the top of the roof. This creates a constant flow of fresh air through the attic, which helps keep the roof deck from overheating.
Because roofs vary in size and configuration, developing an attic ventilation system is a job for a qualified roofing professional.
Install de-icing cables. You can find roof de-icing cables (Frost King’s Roof Cable Kit is a good one) at or at most home improvement stores for $125 to $250. They install directly on top of the shingles via clips over the eaves of the roof. The de-icing cables will work in a pinch to keep ice dams from forming, but they are visible, and raking your roof can dislodge them if you’re not careful.
Invest in a professionally installed de-icing system. A professional system, such as Warmzone’s RoofHeat de-icing system, installs under the roof’s shingles and should be installed by a qualified roofing company at the same time they install new shingles on the roof. These systems will not mar the look of the roofline, and they are designed to last for years. Depending on the size of your roof, a professionally installed de-icing system could add $2,000 to $4,000 to your total roofing cost.
Clear gutters in the fall after trees lose their leaves. Gutters that fill with dead leaves and debris can keep water from draining away through the downspouts as intended. When a gutter is clogged, the melted water from snow will run over the edge of the channel, and when temps dip, it will lead to the formation of icicles and an ice dam that builds back on the roof.
Having the gutters cleaned before winter arrives can prevent roof damage in regions that see heavy snowfall and frigid temps. But don’t teeter precariously on a ladder; use a designated gutter cleaning tool, such as the AgiiMan Gutter Cleaning Tool, to help you safely remove leaves and debris.
If neglected, ice dams can result in significant roof ice damage to a home, including ruining shingles and gutters. Because water can be forced under the shingles and leak into the house, there’s also the risk of interior water damage and mold growth.
Ice dams can be melted away via the use of chemicals or steaming, or they can be physically removed by breaking off small chunks at a time. In the long run, however, the best course of action is to prevent ice dams from forming in the first place by insulating the house and venting the attic correctly. Homeowners should view the cost of having these updates done as an investment in the home’s value.
FAQs About Ice Dam Removal and Prevention
For those living in homes susceptible to ice dam formation, it is only natural to have a few questions about how to deal with the problem and how to best avoid it.
Q. Should you knock down icicles?
Knocking down large icicles that have formed along the roof or gutter edge is dangerous, especially if you’re knocking them down while standing below. It’s usually safe to remove small icicles (less than 1-foot long and ½-inch wide) by nudging them from the back side with a pole or rake, but don’t attempt to knock down enormous ones.
A better option is to hire someone who knows how to remove ice dams or use a calcium chloride ice-melt product, such as Harris’ Kind Melt, on the ice dam and icicles to allow them to melt safely.
Q. Do metal roofs prevent ice dams?
A standing seam metal roof features vertical metal panels that shed snow more easily than shingles so that they will reduce the risk of ice dams, but they can’t always prevent them. An ice dam can still form in the gutter and then build back on a metal roof, and ice can freeze and adhere to the metal as well.
Q. How do you get rid of ice dams fast?
The safest way to get rid of ice dams is to hire a pro. The quickest way is to treat the ice dam with a chemical ice-melt product, and when it begins to melt away, use a mallet to very carefully break off chunks from the edges of the melted channels.