How to safely solve your roof’s ice dam

Most roofs in Canada develop at least some ice each winter, but if it gets more than a couple of inches thick around the eaves, it can cause leaks.

A build-up of ice like this is called an ice dam, and can be problematic because the water that pools behind the dam can work its way under shingles and cause leaking into the home.

So why do some roofs develop large and damaging ice dams around the eaves, while others don't?

It comes down to the temperature of the roof surface. Lack of insulation or insufficient attic ventilation can cause the main part of your roof to become warm enough to melt snow. As this water runs down the roof, it eventually comes to the edge that overhangs the walls, which is always as cold as the surrounding air because there's no attic space underneath to heat it.

The melted water re-freezes as it hits the cold eave area. The longer the weather stays cold enough to freeze water, yet warm enough that snow melts on the main part of the roof, the bigger the ice dams get. Varying weather patterns mean that ice dams get much larger during some winters than others.

There are two ways to stop the ice dam problem. The best option involves boosting attic insulation and ventilation so the roof surface becomes colder. If snow doesn't melt on the main part of the roof, ice dams can't form. A professional insulation contractor can provide you with advice on how to fix the dam, and the best way to do the job. You need a pro for this work – having the correct attic ventilation is important and mistakes can lead to major structure problems over time.

Some home designs make it impractical to increase insulation and ventilation enough to prevent a warm roof surface and resulting ice dams. In cases like these, electric roof heating cables are an effective fix. They provide a heated drainage path that allows melted roof water to make its way off the roof. A little ice may still build up on the eaves with roof heating in place, but it won't get thick enough to cause trouble. A professional roof contractor can install this type of system for you.

If you're looking for a contractor, the Canadian Home Builder's Association offers free unbiased information on how to hire a contractor the smart and safe way. Find more information at www.getitinwriting.ca.