Ice Dams vs. Icicles on Your Roof
Don’t be left out in the cold when it comes to understanding these two winter hazards
Highlights
Ice dams and icicles form from melted snow or ice refreezing at the edge of the roof.
Improper attic insulation, clogged gutters, and roof slope can all cause ice formation.
Icicles are less likely to cause interior damage than ice dams but pose a safety risk.
Fresh snow and ice can make it look like a winter wonderland when you look out your window, but when they’re on your roof, they become a lot less magical. Ice dams and icicles are both ice formations that can cause damage to your home. Learn the difference between ice dams and icicles so you can prevent and remove them before they cause big problems.
What Are the Differences Between Ice Dams and Icicles?
While both of these types of ice formations can appear after winter weather, they’re very different. Ice dams are thick, solid chunks of ice that form at the edge of the roof and force water underneath the shingles. Icicles are usually found hanging from the roof’s eaves and gutters, anchored at the top of the icicle, and hanging freely down into open air.
| Type of Difference | Ice Dams | Icicles |
|---|---|---|
| Location | Roof edge and shingles | Gutters and eaves |
| Shape | Chunk | Cone-shaped |
| Size/Density | Large/thick | Long/thin |
Difference in Causes
Ice dams and icicles are both caused by melting snow or ice that refreezes close to the roof’s edge once temperatures drop again, usually at night. Different factors contribute to forming these two types of ice, however.
Attic Temperature
Attic temperature plays a large role in ice dam formation. Snow and ice melt when warm air escapes from the roof, then refreeze once they reach a colder area at the edge of the roof. Improperly ventilated or insulated attics create heat under snow and ice, causing it to quickly melt and then quickly refreeze once the temperature underneath drops again.
Roof Slope
Icicles often form on houses with steeply sloped roofs. Sun hitting a snowy roof causes rivers of melted water, which refreezes as it drops off the roof and hits the icy air. Ice dams are more likely to form on lower sloped roofs, as they’re usually less ventilated, and drainage is slower than on steep roofs.
Icy Gutters
Gutters that are clogged with large chunks of ice can contribute to both icicles and ice dams. When gutters are blocked, melting water has nowhere to properly drain, so it flows over the gutter and off the roof to form icicles, or it refreezes and backs up onto the roof in large chunks, causing ice dams.
Damage Differences
While ice dams and icicles are both unwelcome sights when it comes to your roof, they can pose risks for different kinds of damage.
Leaks
Ice dams can force melted water to run underneath chunks of frozen ice, unable to drain off the roof properly. This water gets forced up under shingles, saturating the roof deck, and potentially leaking into your home’s interior, running between walls, into the attic, and other areas of your home.
Gutter Damage
Ice dams and icicles can both damage your gutters. The weight of ice in any form can pull the gutters away from your roof. Since ice dams are heavier and take longer to melt, they can damage your gutter system the most.
Mold and Mildew
Any water that makes its way under your roof can cause mold, mildew, or fungus growth. This is a particular worry for ice dams since they’re more likely to cause water intrusion than icicles.
Safety Hazards
Icicles can be bad for your roof, but they can be even worse for you and your family. As you can imagine, pointy, heavy icicles that are able to fall from stories high without warning pose quite a safety risk. Icicles that form over walkways or other heavily trafficked areas can fall and shatter whenever they melt enough or get heavy enough to detach from the eaves or gutters. They then leave ice on the ground, which itself poses a risk of slips and falls.
Prevention Differences
Preventing ice formation is key to preventing the damage that ice dams and icicles can cause.
To prevent ice dams:
Ensure your attic is properly insulated and ventilated to provide a consistent temperature
Keep gutters and downspouts clear of ice and snow
Use a snow rake or brush to clear the roof after snow
Clear gutters in the fall to remove leaves and other debris that can clog them
Use roof heating cables to keep water from refreezing once melted and to keep gutters clear
To prevent icicles:
Keep gutters clear of ice and debris
Use gutter heat tape to keep gutters above freezing and keep water moving in freezing temperatures
Removal Differences
If your prevention methods don’t work, you’ll want to remove these ice formations before they cause damage. Keep in mind that freezing, icy conditions can pose serious safety risks, so call in a local snow removal pro for dangerous tasks that involve climbing a ladder or getting on an icy roof.
"Your attic should be similar temperature to outside, which eliminates the melting on the roof which then will eliminate the ice problems. Keeping your attic cold through insulation on the attic floor and properly functioning ventilation is the solution."
— Todd Miller, President of Isaiah Industries, Piqua, OH
You can knock down icicles, particularly those in high-traffic areas, with a long-handled tool used at a safe distance and from a safe angle where you don’t risk the icicle falling on you.
Ice dams are more difficult to remove since they require getting up on the roof. Play it safe by hiring a pro to remove ice dams—the cost to remove ice dams will save you from expensive repair bills and potentially serious injuries. If you see signs of an ice dam, don’t try to handle it yourself.
Frequently Asked Questions
Metal roofs and steeply pitched roofs are less prone to ice dams than other kinds of roofs. Metal roofs distribute heat differently, making them less likely to have inconsistent temperatures that lead to melting and refreezing, and steeply pitched roofs drain water faster as long as gutters and downspouts are kept clear.
It is not advisable to use salt on your roof to prevent or remove ice dams. It’s not only mostly ineffective but can also cause serious damage to your roof itself. Salt can rust metal, damage masonry, pit shingles, and cause runoff that’s damaging to plants and animals.
A new roof may improve insulation and ventilation problems that can lead to ice dams, but it’s not a solution for preventing them. All roofs are susceptible to the conditions that cause ice dams, so it’s best to invest your money into insulation and gutter management solutions rather than a new roof if you don’t need a replacement yet.