Ice Dams – Everything you need to know [Update 2019]

By Juno Construction

Ice dams can be a major headache during the winter. Luckily, we've compiled all the information you need. If your home is suffering from ice dams, you've come to the right place.
Share on facebook
Share on twitter

What are Ice Dams

An ice dam is essentially a build-up of ice that accumulates on a roof’s eaves (see picture below). When the snow melts on a roof, either from the sun or heat loss in the attic, water will migrate down the roof and freeze on the eaves of your roof. These ice mounds will continue to build as long as they are being fed by a continuous snow/melt cycle.


Graphic illustrating the formation of an ice dam



Ice dams should not be taken lightly. If left unattended, they can damage your gutters and shingles. As water continues damming up behind the ice mound, it will search for ways to migrate underneath the shingles and move into the attic, insulation, walls, ceilings, and other areas of the home. These leaks are not only aesthetically displeasing but can cause mold growth, and break down drywall and other structural components such as support beams.



Mold in the home caused by water intrusion



The solution to the ice dam issue may seem simple, but there are several directions one can take to mitigate the problem. Let’s first talk about why they occur.

Why Do Ice Dams Occur

You may be wondering what the core issue to the ice dam problem is. At first glance, it may appear that snowmelt is the real issue. However, have you noticed how some of your neighbors seem to have an even layer of snow (not melting) covering their roof while your roof is ice dam ridden with scattered areas of snow?

This example demonstrates that snowmelt on the roof is only a by-product of an underlying problem. Why is the snow melting in the first place? Because bystanders cannot visualize the real issue from outside of the home, it isn’t obvious.


Comparison of a house with heat loss vs a house without heatloss


The real reason that ice dams occur is heat loss from the attic.

That means that heat from the conditioned living space (your home) is moving into the unconditioned living space (your attic) where it rises and melts the snow on your roof deck. Aha! The cause of the melting snow.


heat loss from the attic causing the snow on a roof to melt
Heat loss in the attic will melt snow on the roof. This meltwater will run down the roof and freeze on the eaves, creating an ice dam.



The attic is meant to be a cold space for reasons beyond just eliminating ice dams. When heat flows into the attic and meets the cool air, condensation is formed and will stick to metals first and wood structures second. When temperatures drop, this condensation will freeze and become visible as frost.



Frost in the attic



When temperatures rise again, condensation melts and drips all over insulation and other critical attic components. This moisture is dangerous for several reasons:

  1. The attic is at high risk for mold growth: Mold is a serious health hazard to people and building materials alike. As long as it lives, it will continue to break down your attic components and jeopardize the home dwellers health.

  2. Roof deck plywood can become delaminated from exposure to moisture: The best way to correct roof deck that has become delaminated is to replace it…expensive!

  3. Attic insulation becomes damp: Damp attic insulation means it cannot resist heat flow the way it was designed. It is no longer an effective insulator (keeping heat out of the attic), but acts more like a conductor of heat, allowing heat to enter the attic space.


Wet insulation & mold growth
Wet insulation & mold growth


How Heat Enters an Attic

Many people assume that the best way to keep heat out of an attic is to add more insulation. While an adequate amount of insulation is important, it cannot fix the issue while standing alone.




There are 3 attic components essential to a proper functioning attic

The first component is insulation which we have already touched on. Insulation is important because it acts as an insulator and helps to keep heat out of the unconditioned attic space.


Correctly installed insulation helps to prevent heat loss in the attic
Correctly installed insulation helps to prevent heat loss in the attic


However, without the second component, sealed bypass, attic insulation is rendered useless. An attic bypass is any open area between the living space and attic such as chimneys, ceiling light fixtures, heating ducts, kitchen and bath exhaust fans, plumbing, electrical wires, dropped ceilings and soffits. All of these openings, if left open, will allow heat to flow right into the attic. A professional need to close these off.


Correctly sealed bypass
Sealing air leaks is crucial to preventing heat loss


The third essential component is ventilation. Correct attic ventilation will help to ensure the attic stays cool. When all three attic components are functioning together, an unbeatable system is formed. Serious ice dams will no longer be in the cards!


Appropriate install of air chute and wind wash
Appropriate install of air chute and wind wash


Preventing Ice Dams

Now that you have some information on what ice dams are and why they form (HEAT LOSS), we can talk about prevention. The number one recommendation for overall attic and roof health is to have a professional perform an attic/roof inspection. They can safely investigate the intricacies of your attic and determine if the attic system is functioning at its highest potential. If they find shortcomings (ie, open bypass or lack of insulation) they can work with you on a plan/scope of work to fix the issues.


A engineer preforming a professional roof inspection


Now we understand that everyone has a budget and correcting attic issues may not fit into that budget initially (it’s good to have a free inspection anyway so you can start planning for the future). Luckily, there are some less expensive ways to prevent ice dams from forming and causing harm.

Snow Removal Services

Many contractors provide snow removal services. Remember an ice dam forms when the snow melts and freezes on the roof eaves. Removing the snow takes away the moisture required for an ice dam to form. It is especially imperative to have snow removed if you already have an existing ice dam.

It’s better to remove the snow before it can feed the ice monster living on your roof eaves. The longer water is left to dam up behind the blockage, the higher at risk your home is for leaks.  Make sure the snow removal contractor you hire is experienced and uses damage-free methods in order to preserve your shingles.


Roof that has had snow shoveled off of it
Removing snow will temporarily eliminate ice dams and help prevent leaks


Prevention methods to avoid:

  1. Heat Cables: Steer clear from prevention methods like heat cables. They operate by melting a portion of the ice dam with the intention of allowing roof water to move through the ice dam and into the gutter. However, they often are not effective and the ice dam persists. On top of this, leaks can still occur, electric bills increase, and they must be monitored to prevent overheating or, in rare occasions, fire.


A roof with heating cables


  1. Salt-Filled Pantyhose: Some people fill pantyhose with salt and lie them vertically across existing ice dams on their roof. The thought process is that the salt with melt a path through the ice dam which will allow water to move through the dam and into the gutter. Please don’t entertain this idea. Salt is just not good for your roof in general. You may end up dealing with issues like discolored shingles, rusty or corroded flashing, nails, and gutters, tarnished driveways & walkways, dead grass &  shrubbery and leaks (saltwater).


Salt filled pantyhose on roof


Check out our post on ice dam removal tactics to avoid.

Ice Dam Removal

If you already have ice dams, they should be removed. An experienced professional can help you with this. They will use methods that avoid damage to your shingles and/or gutters. Avoid a professional who endorses “tactics” such as steaming which involves spraying warm steam on the ice dam to melt it. Adding water to a roof is always a bad idea. This water can work its way into the underlayment’s and freeze or accumulate near the foundation which can be detrimental to your home.



Look to hire a professional who understands the science behind ice dam formation. They would know that the roof deck will be warmest within the first 6 feet of the roof eaves. This part of the roof is where the majority of the snow will melt and continue to feed the building ice dam.

Because of this, they will shovel all the snow within the first 6 feet of the ice dam and then carefully remove the ice dam itself with safe tools. Typically, about ½” of ice will be left on the roof eaves in order to prevent shingle or gutter damage. The sun will be responsible for melting away any remaining ice.


Ice dam removal results




Ultimately, ice dams are dangerous the health of your home. Whether you choose to invest the time and money to seal air passages in the attic for long-term ice dam prevention or if you hire a contractor to remove roof snow after storms for a temporary fix, the important thing is that the ice dam is being taken care of. If left to thrive, leaks and other issues can occur. Be sure to speak with your trusted contractor to determine the best ice dam eradication strategy for your home and family.

Spread the word

Share on facebook
Share on twitter
Share on linkedin
Share on email