Winter can be a wonderful time of year filled with snowy landscapes and holiday parties. But it’s also a season that can take a toll on your roof, especially when you find yourself dealing with ice buildup or ‘ice dams’.

Ice dams can cause significant damage to your roof, upsetting family routines and leading to costly repairs. Prevention is key to avoiding this winter-related roofing problem.

Our Montreal roofers take a closer look at what causes ice dams and how to prevent them from forming.

What is an ice dam?

An accumulation of ice on a roof, often referred to as an ‘ice dam’, is a common local phenomenon. Ice dams form when the temperature inside the room just underneath the roof remains above freezing, causing the snow in contact with the roof to partially melt.

Water from the melted snow proceeds to flow to the edge of the roof where, away from the warmth, it refreezes. The process repeats until, layer by layer, a solid sheet of ice or ‘ice dam’ takes form. They are not only messy to look at – ice dams can cause significant damage to both the roof and structure of a building.

What causes ice dams to form?

To prevent damage from ice dams, it helps to be aware of what factors make them more likely to form. The following are some common causes we have observed in Quebec.

Poor insulation

Poor insulation in upper rooms allows heat to seep out to the roof. This melts any accumulated snow, which in turn forms an ice dam. Our experienced roofers can easily identify the cause of your ice dam, and if upper room insulation is the root of the problem, they can fix it.

Inadequate ventilation

If warm, moist air remains trapped in your house, it can contribute to the formation of an ice dam. Make sure that your home’s ventilation system is in good working order and is powerful enough to protect your roof.

Roof layout

The shape of your roof can also be a contributing factor to ice damming. For example, low-slope or flat roofs are more prone to ice buildup than pitched roofs. It is important to take this into consideration when planning any roofing work.

Exposure to sun

Sunlight can play a role in ice dam formation. Contrary to what you may think, roofs that receive less sunlight may be more prone to ice buildup, because snow and ice will melt when temperatures rise, but will be less likely to melt completely or slide off the roof without direct sun. Instead, they will refreeze, creating an ice dam.

Heavy snowfall

Thin patches of snow here and there on your roof do not cause trouble. However, a snowfall of 4 to 6 inches or more on the roof can be dangerous, especially when combined with cold weather. That’s why Les Couvruers Duro-Toit specialize in roof snow removal to help you through even the harshest Quebec winters!

The consequences of an ice dam on the roof

Ice buildup on a roof can lead to a variety of negative consequences. Check out the main risks below.

Roof collapse

The extra weight caused by ice build-up can damage the roof structure and, in extreme cases, cause it to collapse. In addition, ice can damage gutters and downspouts, leading to water leaking into the home.

Water infiltration

Ice dams can also lead to water infiltration in your attic and house, as melting ice leaks into the building, damaging walls and ceilings. In addition, pressure from an ice dam can cause existing cracks or leaks to worsen.

Increased heating costs

Ice dams can also lead to increased heating costs, as a poorly insulated roof – the root of the problem – makes it possible for heat to escape the building.


Ice formation can also pose a safety risk. If a chunk of ice falls off the roof, it could damage a car, break a window or even injure a bystander. Yet another reason to clean ice off your roof regularly.

How to prevent ice dams

There are several things you can do to prevent ice dams from forming on your roof and minimize the risk of related damage:

De-icing cables (heat cables)

Roof de-icing cables use heat created by an electrical system to limit the formation of ice. They can be placed along eaves, around skylights or chimneys, or near gutters and drainpipes. Note that heat generated by de-icing cables is not always enough to prevent ice dam formation. Clearing the snow to prevent ice from forming in the first place is a more reliable solution.

Snow removal

Removing snow from the lower sections of your roof is a simple and effective way to prevent ice build-up. You can do this yourself, but there are good reasons to turn to experienced roofers for this job. Professional methods and equipment are the only way to be absolutely sure your home will stay protected from water infiltration.

Attic insulation

High-quality upper-room insulation is essential to prevent ice dams from forming. The job must be done thoroughly to avoid creating thermal bridges, which can in turn create more ice. Air leaks between attics and lower floors should also be blocked to control the flow of warm air.

Rain trough maintenance

Everyone needs to clean their gutters and rain troughs regularly to keep them functioning properly and to prevent the risk of ice and water build-up on the roof. We recommend hiring a professional on an annual basis to ensure that the cleaning is done properly.

Les Couvreurs Duro-Toit can protect your roof from ice dams!

Don’t wait until it’s too late! If you aren’t sure whether your roof is winter-ready, contact our experts ASAP. The well-being of your family may depend on it!

In addition to offering snow removal services, we also conduct roof inspections before winter sets in. When it comes to making sure you’re warm and cozy during the coldest season, Les Couvreurs Duro-Toit have you covered! Contact us by phone at (514) 755 – 8648 or use the form on our contact page.

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