Ice dam prevention: how to save your roof from this icy hazard

Image source: Erie Insurance

Gianna Cappuccio

By Gianna Cappuccio

February 26, 2021


When winter waltzes into the lives of homeowners living in cold-winter climates, there’s no denying that it’s here to stay. Gearing up for the first big snowfall of the season may have you lugging out the shovels and salting the sidewalks, but your driveway isn’t the only part of your home that’ll need snow removal.

Your roof is bound to collect a massive amount of snow, especially during multiple snowfalls throughout the winter. This build-up can result in a homeowner’s worst nightmare – ice dams.

In this article, we’ll teach you a few tips and tricks on how to prevent ice dams. Let’s dive in.

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What is an ice dam?

Ice dam and icicles on a residential roof

Image source: MPR News

An ice dam is a build-up of ice and snow that typically forms on the eaves of sloped roofs of heated buildings. Ice dams have the potential to weigh hundreds of pounds, depending on the amount of buildup that's been left stagnant on your roof. These heavy sheets of snow and ice are not only unseemly – they can do serious damage to the structure of your roof eaves.

The weight of an ice dam isn't the only way it can damage your roof. At their core, ice dams are water. As an ice dam beings to melt, meltwater can seep into and back up under your shingles and flow down into your ceiling or walls, essentially ruining them. If ignored, ice dams pose a greater threat to your roofing, interior drywall, gutters, paint, insulation, and so much more.

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How does an ice dam form?

A graphic illustrating how an ice dam forms as warm air melts the snow and cool air causes it to refreeze

Ice dams are formed when snow begins to melt on an upper, warmer part of your roof. Ice dams can only form when the space inside your attic along the underside of your roof deck is above the freezing point of water. The warm air beneath the roof will heat your shingles, and thus the ice sitting on your roof, causing it to melt and flow to the overhanging eave structure, where it will refreeze. This is where ice dams begin to do some serious damage.

As the ice accumulates, it forms a blockage that prevents melting snow and ice from flowing freely off the roof. The melted snow will refreeze, backing up under your shingles where it will inevitably melt again, soaking through to the roof sheathing and leaking into your attic space. Soon, it will leak through to the insulation, and then through to the drywall and ceiling below, and eventually into your living space, causing serious water damage.

How to prevent ice dams

Suburban home covered in ice dams

Image source: WBUR News

While ice dams may seem daunting and dangerous, they can be prevented. The key to preventing ice dams is to keep your roof cold to ensure the ice and snow sitting on your roof do not melt. A cold roof will be covered in a thick layer of snow while a warm roof will be patchy where the snow has melted. You may even notice a few icicles hanging from the eaves.

Ice dams can be prevented through a combination of the following:

  • Closing up any and all attic bypasses
  • Insulation
  • Adding ridge vents and soffit vents to your roof
  • Electric heat cables

Preventing ice dams by closing up attic bypasses

Unfinished attic in a suburban home

Image source: YellowBlue Tech

Just as the human body loses most of its heat through the head, most homes experience heat loss through the ceiling into the attic. These warm air leaks are most often caused by chimneys, cracks in the drywall, unblocked exterior walls, cracks around light fixtures, or plumbing pipes.

To stop these air leaks in their tracks, you'll need to venture into your attic. Be sure to schedule these repairs on a cooler day, as your attic will be unbearably hot otherwise. Once you're in your attic, you'll need to rake back your insulation and plug each leak with foam insulation or caulk, which can be found at your local hardware store. Whenever you're dealing with insulation, always wear a dust mask and a long sleeve shirt to help prevent irritants from the insulation from getting on your skin.

Preventing ice dams with attic insulation

Professional spraying foam insulation onto exposed attic walls

Image source: Utah Energy Savers

Insulating your attic is your next best defense against ice dams. Choosing insulation with a high R-value will ensure your insulation will perform at its best.

If you have an open attic, you'll need to pay the most attention to insulating your attic floor. If your second story is finished and your ceiling sits flush against the underside of the roof, you'll need to insulate the rafter spaces. Insulating this area is enhanced with the help of ventilation baffles, which provide a channel for air to flow from your exterior soffit vents up into your attic space.

These insulation methods will prevent hot air from reaching the roof deck and heating it to a point where the snow will begin to melt. Fiberglass insulation is recommended for hard-to-reach areas such as a roof or unfinished attic.

Preventing ice dams with ridge vents and soffit vents

Ridge vents Soffit vents

Ridge vents and soffit vents on suburban homes. Image sources: Grant New Homes & Lindus Construction

Roof ventilation is essential in the prevention of ice dams. Ridge and soffit vents are two such forms of ventilation that will draw in the chilly outdoor air and flush out the warm air, cooling both your attic and roof in the process.

If you choose to go with a ridge-and-soffit vent system, you'll need to install insulation baffles on the lower side of your roof, above the exterior walls. The baffles help to create a 1-to-2-inch channel of airflow. Without the baffles, thick insulation can potentially block any airflow, leaving you with a hot attic, a cold roof, and more ice dams than you know what to do with.

Preventing ice dams with electric heat cables

Electric heat cables in a zigzag pattern on a residential roof

Image source: Nitro Electric

If improving ventilation and insulation simply are not practical solutions to your ice dam problem, an electric heat cable is sure to do the trick. Electric heat cables are high-resistance wires that can be mounted to your roof in a zigzag pattern and plugged into an outdoor GFCI outlet. These cables will prevent the melting water from cooling and refreezing once it reaches the eaves.

Unfortunately, electric heat cables are neither the most attractive nor the easiest to install. If you opt for the electric heat cable route, you'll need to reroute the meltwater that's flowing off your roof or it will reach the gutters and refreeze. Running a heat cable inside a downspout is the best way to ensure it doesn't clog with ice.

Ice dam removal

If you find your roof shingles are already plagued with ice dams, never fear. We’ll teach you how to remove them if you haven’t gotten the chance to prevent them.

Use a roof rake after heavy snowfalls

A homeowner using a roof rake to clear snow from his roof

Image source: Garage Tool Advisor

Use a roof or snow rake to clear snow from your roof surface as soon as possible after a heavy snowfall. We recommend using a long-handled roof rake to remove snow that has gathered at least four feet above the edge of the roof. Don't scrape too hard, though, or you can risk damaging your shingles. This snow removal technique can prevent ice dams from forming and is the safest way to clear snow from your roof.

Use calcium chloride or rock salt to melt the ice

If you see an ice dam beginning to form, you can apply calcium chloride, rock salt, or any other ice melt product to the ice. If you've heard the odd home remedy involving stuffing calcium chloride into a leg of old pantyhose and shoving it up against your gutters to melt the snow, forget about it. This method has been proven to be more trouble than it's worth!

Break up the ice dam

A homeowner using a hammer to break up an ice dam on their roof

Image source: MeltSnow

While you should never attempt to climb onto your roof to remove an ice dam, you can reach eaves, and the offending sheet of ice, with an extension ladder. Once you've located the ice dam, you can begin to chip away at it with an ice pick, chisel, or small hammer. Breaking up the entire ice dam isn't necessary, as whatever you have chipped away will create a small channel for water to flow through. This method requires a lot of repeated work, though, as the water may refreeze over the channel you've created.

Hire a professional

If you’d rather avoid the DIY route, we recommend hiring a professional to remove the ice dams. A professional will remove your ice dams with heavy-duty equipment, such as a high-temperature steamer, that you may not have access to. While this service may cost a pretty penny, it’s well worth the price to prevent irreparable damage to your roof.

Ice dam prevention: in summary

Suburban home in winter

Image source:

The best way to save your roof from costly repairs once winter is through? Ice dam prevention. There are several relatively inexpensive methods to choose from, and we suggest hopping on the prevention train before your ice dam problem costs you more than just a few hours of hard labor. Fully-formed ice dams can be removed, but if you aren’t willing to do the job yourself, hiring a professional is always an option.

After the snow melts and spring is ushered in by warmer weather and longer days, you can head into next winter with confidence and a few tricks up your sleeve on how to prevent ice dams.

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