Have you ever looked up onto your roof in the winter and spotted a big barrier of ice near its edge? Perhaps there were also many icicles. This wall of ice is commonly known as an ice dam, and even though they are common, it is not good to have one on your roof. Here's a look at the hazards posed by ice dams, and what you can do to prevent them in the future.

What damage do ice dams cause?

Ice dams make roof leaks increasingly likely. As the temperature changes, the ice may begin to thaw, and some of the water may work its way under the shingles near the edge of the roof. When the temperature drops again, this water expands as it re-freezes, prying the shingles away from the roof and making leaks likely. Ice dams also "clog" your gutter, so water sits on your roof for longer rather than draining away. This, again, makes leaks more likely, and the increased exposure to moisture also causes issues like rotting and algae growth.

What causes ice dams?

In order to understand how to prevent ice dams, you must first understand what causes them. In an ideal situation, your roof would be well insulated, so the heat from your home would not transfer to the roof – it would stay cool, and the snow on top of it would not melt until the temperature rose above freezing.  If you do not have enough insulation in your attic, however, the top of your roof may become warm from the heat escaping your home. This cause the snow to melt and trickle towards the edge of the roof, where it re-freezes and forms an ice dam.

How can ice dams be prevented?

If you're noticing ice dams on your roof, the long-term solution is to add more insulation to your attic. In many homes, simply laying out another layer of fiberglass insulation is sufficient. However, if you live in an old home with thin walls, there may not be enough space for the amount of fiberglass insulation it will take to adequately insulate your attic. Having it replaced with high-R-value spray foam insulation may be required.

In the short-term, while you're waiting to improve your insulation, you can prevent ice dams from forming by raking the snow off of your roof before it has a chance to melt. Snow rakes, which are like lawn rakes with long handles, are sold at most garden stores and make it rather easy to clear your roof after a snow storm.

For more information, contact a residential roofing contractor in your area.