You might admire them gleaming in the sunlight or even sneak a lick from one you snap off the roof, but icicles aren’t as innocuous as they seem. In fact, they’re a sign that your home could be vulnerable to a condition called ice dams. Here’s what you should know about how to identify ice dams, how to remove them, and how to keep them from coming back so you can prevent these ice buildups from damaging your home.
What is an ice dam?
An ice dam is a ridge of ice that forms along the eaves of your home. It develops over several days or weeks as the snow on your roof melts in warmer daytime temperatures and then refreezes overnight. The ridge of solid ice that forms can grow thick enough to prevent new snowmelt from draining off the roof, forcing it under your shingles and even into your attic.
Ice dams are most common in climates that experience a significant amount of snow and sustained subzero temperatures.[1] They need two conditions to form: an accumulation of snow and an uneven surface temperature. Part of the roof must be warm enough for snow to melt, and the eaves, which are the part of the roof that extends beyond the walls of your home, must stay cold enough for the ice ridge to form and stay frozen. All of this sounds very specific, but it only takes an inch or two of snow on your roof for an ice dam to form.[2]
The same conditions that cause ice dams also cause icicles, so a large collection of icicles hanging off your roof are your first clue that you might have an ice dam.
Understanding the life cycle of an ice dam
An ice dam’s life cycle has three stages. The better you understand each, the better you’ll be able to prevent or remove ice dams from your property.
Birth: Heat from inside the house warms the roof, but it does so unevenly — the eaves stay below freezing, but the temperature on the rest of the roof warms enough to melt snow.
Growth: As the snow melts, it runs down the roof and freezes along the eaves. The ice isn’t dangerous at this point, but it sets the stage for a dam to form.
Maturity: Snow continues to melt. The built-up ice prevents the water from draining off the roof, so it backs up behind the dam and works its way under the shingles and into the exterior walls. The longer the dam goes unnoticed, the more serious damage it might cause.
Why are ice dams bad?
Ice dams are problematic for two reasons: First, they can damage your home and promote roof leaks. Second, they can result in injuries to people who walk beneath them.
In addition to damage to gutters, shingles, and the structure of the roof from the weight of accumulated ice, ice dams can cause water to leak into your home. They do this by preventing snowmelt from draining, which causes it to back up behind the dam.
This backed-up water remains melted because of the warmer roof temperature and can seep into cracks and openings in the roofing material. From there, the water can drain into exterior walls and through the insulation in your ceiling, causing visible stains on the ceiling finish.
Seepage can promote the growth of mold and mildew, which can cause respiratory problems.[3]
Ice dams also pose a threat to people outside your home. If a section of the ice dam breaks off and falls to the ground — or knocks a gutter down — people standing below can suffer serious injuries. Slips and falls may also occur if the ground becomes slick from fallen ice or snowmelt that refreezes.
How to remove ice dams from your roof
You have several options for removing ice dams that have formed on your roof.
Cold air
Put a box fan in the attic and aim it at the underside of the roof. The fan’s cold air will freeze the water and prevent it from leaking into the attic.
Snow rake
Snow rakes are designed specifically to remove snow from your roof. The rake has a long handle and a wide head that resembles that of a push broom but without the bristles.
Remove the snow by extending the rake three to four feet up the roof and then sliding it down, pulling down snow in the process. Just be careful not to scrape so hard that you damage the surface of your shingles. Plan to use your rake after each heavy snowfall.
Calcium chloride
The same product you use to melt ice on your driveway will also melt ice on your roof. Fill old pantyhose with calcium chloride (not rock salt) and position them perpendicular to and crossing over the dam. As the calcium chloride melts the ice, it’ll create a channel that will allow snowmelt to drain.
Garden hose
Hosing down the ice dam will help melt it as long as you do it on a warm day. Start at the bottom edge and work your way up to create channels in the ice.
Hire a professional
Working on a snow-covered roof or below a heavy ice dam is dangerous to both you and your home. If in doubt about your ability to remove ice and snow without damaging the roof or injuring yourself, hire a professional to do the job for you.
Avoid these tactics when removing ice dams
Not all ice dam removal methods are worth trying. It’s best to avoid the following tactics.
Heat tape and heat cables
Heat tape or cables installed on your roof can prevent ice dams by keeping ice from forming. But they’re expensive to operate, and they must be installed before the weather turns cold. The U.S. Department of Energy warns that heat tape can damage shingles, and heat cable fasteners can provide a place for water to leak through.[4] It’s also possible for ice dams to still form above either.
Clearing ice and snow with equipment not made for that purpose
Chipping ice from the edge of the roof using a hammer, shovel, crowbar or other tool can injure you and damage your roof.
How to prevent ice dams from coming back
There’s no guarantee that any particular method will get rid of ice dams for good, but you can greatly reduce the chance they’ll come back with these strategies.
Seal and insulate your ceilings
Reduce heat transfer from the heated areas of your home to the attic — and keep the roof colder as result — by sealing up your ceilings to prevent air leaks. Once it’s been sealed, consider adding insulation to the ceiling or roof.
Contact your utility company before you start. You might be eligible for rebates on an energy assessment and sealing and insulation projects.[5]
It’s also important to note that a colder roof means more snow accumulation. If you’re not sure your roof can withstand the weight, have it evaluated by an engineer.
Clean the gutters and downspouts
Clogged gutters and downspouts can let snowmelt accumulate and ultimately freeze. Keep the drains clear so water can flow through as the snow melts.
Ensure proper ventilation in your attic
Natural ventilation will help keep your roof temperature consistent. Aim for at least one square foot of opening for every 300 square feet of attic floor.
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