All About Ice Dams and How to Avoid Them

Ice dams avoid Toronto roofs

Central Mississauga townhouse with dangerous icicles forming from melting snow. You definitely want to avoid this!

Winter is here in Toronto!  Beautiful but dangerous icicles forming on the  Distillery District's roofs

Winter is here in Toronto! Beautiful but dangerous icicles forming on the Distillery District’s roofs

Now that Toronto’s winter has officially started (or will be, depending on when you read this) with the first snowfall, it’s time to talk about the dreaded ice dams that destroy many roofs during this season.

What Are Ice Dams?

Ice dams are formed by continual thawing and freezing of melting snow. Often, heat escaping from a home will cause this event to occur. When snow on the upper part of a roof melts, the water runs down the rest of the roof and freezes, forming thick ice sheets. Over time, the water runs down to the edge of the roof, where it refreezes creating a dam. As more and more water makes its way down the roof, it creates a pool. Gradually, the pooled water will make its way back up the roof, getting under the shingles and eventually causing leaks.

Snow melting from the top of the roof due to inadequate insulation and venting

Snow melting from the top of this Toronto roof will slowly contribute to the formation of ice dams throughout the winter months

What Are the Causes of Ice Dams?

The main cause of ice dams is too much heat escaping through the rough due to insufficient attic insulation. Also, improper attic venting can be an issue as well as poorly placed gutters on a roof. A professional roofing contractor will be able to tell what the problem is on site.

Midtown Toronto towhnhomes ice dams forming

Midtown Toronto towhnhomes ice dams forming

On the other hand, the event may be naturally occurring, as a roof that is continually exposed to bright sunshine will certainly have melting snow. Finally, inclement weather can be a factor, with icy and stormy conditions one day and balmy days the next adding to the melting and ice accumulation on Toronto roofs.

How Do I Avoid Ice Dams?

Improving attic insulation so that the warm attic air does not reach the roof’s cold surface will reduce melting snow. In addition, having a roofing contractor assess one’s attic’s ventilation system will keep the attic space cooler, further reducing melting due to the temperature variance. Also, gutters and eaves troughs should be lower than the slope of the roof, ensuring that water, snow and ice are able to easily drain. Finally, installing an ice and water shield membrane in high-risk areas is a necessity on every Toronto roof. This is a second line of defense in case water gets under shingles, stopping any water or ice from penetrating the roof deck.

snow in roof valley

Where snow and ice collects, that’s where Ice and water shield membranes are a necessity– like in this detached home’s valleys

Since ice dams can be naturally occurring, and even the best ventilation and insulation may not be enough to prevent it from happening, on your next re-roof, make sure that you hire a roofing contractor that installs protective membranes all over your roof, as well as an ice and water membrane on the areas most vulnerable to ice dams. At Archer Roofing, we take pride in our work and always use preventative measures, like our insistence on quality shingles as well as a synthetic underlayment and ice and water shields on every roof we install. Contact the best roofing contractors in Toronto for a free inspection or to discuss your roofing needs.


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