Ice Dams – What Are They, And Why Do I Need To Remove Them?

Four-storey ice dam in Boston, MA, February 2015

This massive ice dam took nearly two hours to break down with a cherry-picker and a chain saw.

This winter has been especially brutal for Boston. Just this week, Boston claimed the #2 spot for snowiest winters in recorded history. Snow records have just been shattered in Massachusetts, and most of it has occurred in the last 30 days. Because of these brutal conditions, ice dams are especially dangerous right now.

When the snow piles up on your roof, it will begin to melt and drain to the bottom. This melting is accelerated by having the heat on, but it will happen from the sun as well. The area of your roof that is over your house is particularly warm because the heat from your house rises up and warms the roof. However, the edges, where there is no heat source underneath, are always going to be cold. Over these overhangs, where the gutters are on your roof, the melting water re-freezes, and turns to thick ice. The area where the ice meets the warm part of the roof continues to melt, and push water further up the shingles. This can cause leaking, where this water gets underneath your shingles and into the wood, and eventually manifests itself by dripping out from your ceilings, windowsills, or walls. You will notice that the icicles are growing to enormous proportions. Usually, if your icicles are more than 3-4″ in diameter at the base, that is evidence of an ice dam.

How an ice dam is formed

Without proper treatment, this cycle of ice melting and re-freezing will cause the ice dam to grow and grow. This adds a lot of weight on your roof, and in the sub-layers underneath the roof. You have to keep in mind – the water will saturate your wood an shingles and those will freeze as well. The ice dam that you can see is not everything – it can go deeper into the walls and other voids of your house if the water does not have a place to drain. This leads to the all-important question:

What should you do to about the ice dams? 

To alleviate the situation, you will need to clear off your roof. Depending on the slope of your roof, you may want to get up on it with shovels. If it is too steep, you can clear it off using snow rakes. If you are able to clear all the snow off of your roof, that is the best method. If you are unable to get up onto the roof to fully clear it off, it is important to clear at least a few feet above the ice dams. As a general rule of thumb, clearing about 4′ of snow from the edge of the roof should allow space for the remaining snow and to melt and drain off properly, as long as you follow the next steps.

Once the roof has been cleared of any snow or loose ice chunks, you’ll want to do something about the ice dam itself. If possible, you can hammer away at the chunks and remove what is able to come up easily. You could use a heat gun to help soften the ice for you. Remember though – even if you clear off every piece of ice from your roof, there are still layers of ice that are deeper than what you can see. That means that until it gets warmer, you most likely won’t be able to fully remove the ice dam. Instead, the most important thing to do is to create channels for the water to drain down.

Some people will create channels in the ice dams with hammers, saws, or other tools. Some people will only use Roofmelt (a type of ice-melting rock-salt product that is safe for roofs, usually composed of Calcium Chloride). We’ve found the most effective method is a combination of both. You will want to cut away some channels so that water can drain through, and then apply Calcium Chloride to the area just above the ice dam. By applying the product above the ice dam, it will seep down and continue to keep your channel clear and let the water drain down off of your roof.