Ice Dams And Your Roof

Even though I live in a warmer climate where it does not snow very often -- maybe a spattering that doesn't even stick to the ground once a year or once every other year -- I'm still fascinated by cold weather and the measures that people have to take to protect their homes from the perils of frigid temperatures. For people like me, who see frosty temperatures of around 60 degrees Fahrenheit in the dead of winter, the sight of icicles on a roof is a beautiful albeit foreign anomaly. However, as Mike has pointed out, icicles can be a sign of bigger problems. If it's snowy outside, and the snow on the roof melts, rolls down, and refreezes on lower parts of the roof, a dam of thick ice forms which blocks water from flowing down and off the roof. Roofs are sloped downward for a reason, and when moisture cannot run off a roof, it can get under shingles and into attics. When melted snow and ice goes rogue and then refreezes, it can cause some spectacular damage! In this article that I found on the Canadian website onthego.to, Mike Holmes talks about ice dams, and why it's very important to keep them in check. And as far as people dying from falling icicles... yikes. I sliced my finger on a jagged piece of an ice cube once, and it was one of the most painful cuts I've ever experienced! Just a side note...


 
From OnTheGo.to:

Ice Dams & Your Roof - By Mike Holmes

Many people think snow-covered roofs dripping with icicles look beautiful. But if it was my house I’d be worried. Icicles can be dangerous. They’re also a sign of an ice dam — which can lead to bigger problems.
An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow from draining away through your eavestroughs and downspouts.
For an ice dam to form there has to be snow on the roof. This snow starts to melt — either from the heat of the sun, or from heat escaping from the attic. This water flows down the roof under the snow and re-freezes when it reaches an unheated portion of the roof — usually at the eaves — where it starts to build into an ice dam. The ice dam grows through a cycle of freezing and thawing, and can get very thick. It can also spill over your eaves and form those ‘beautiful’ icicles.
Ice dams can also form on houses that have complicated roof designs — especially around skylights because they have less insulation around them allowing heat to escape.
Ice dams prevent water from flowing down. It will eventually back up, finding its way under the shingles and into the attic. A thick ice dam can damage roof flashing, fascia and soffits. It can even shift vent stacks and create gaps that allow water into your roof. That water can flow into your exterior wall cavities and end up in your basement. Or it can leak into your home and cause damage to walls, ceilings and insulation.
That’s why I’m a big fan of ice and water shield. It forms a barrier to water and helps prevent moisture from working its way into your home. Minimum code calls for roofing felt over the entire roof and ice and water shield just along the eaves. But I think it should be used all over the roof as a secondary membrane. If you have an ice dam you might be tempted to use heating cables on your roof and eavestroughs. But this doesn’t solve the problem. To get rid of them for good your attic must be properly insulated and ventilated.
Your attic is a cold zone — the attic temperature should be the same as the air outside. If there’s enough insulation in the attic it will stop heat from escaping and melting the snow on the roof. Proper ventilation keeps the exterior of your roof uniformly cold. If your roof stays cold the snow won’t melt. Also make sure you have enough roof vents — and that they aren’t covered by insulation on the inside or snow on the outside.
If you have an ice dam don’t try to remove it yourself. It’s dangerous — for you and for your shingles. You can slip, your ladder can slip, and removing ice from the edge of a sloped roof can release chunks of ice higher up that can slide down towards you, tearing shingles on the way. People have died from icicles falling from their roof. Get a professional with the proper equipment and training to remove it for you.