Q & A - Icicles and Ice Dams - Causes and Cures

Icicles and ice dams seem to be on everyone's mine this winter in the north-east of our country.

Sue had a brand new roof put on in Oct of 2014 and has a couple of leaks and icicles she is dealing with this winter with all the extreme snowfall. This is a good photo that helps explain what can be one of the causes of ice dams and icicles. She had un-melted snow on her garage. No one heats the garage so it does not melt under 32 degrees, whereas, on her new roof above the living area of the house the snow is melted. This can be caused by heat loss from the living space rising into the attic and melting the snow on the roof.

The effect of this water when it gets near the overhangs and rain gutters and the temperatures are still freezing is the formation of ice dams. These ice dams literally cause a back up of water, just like a small lake at the edge of the roof. This water can easily submerge the roofing shingles and intrude into the inside of the home if a special ice and water barrier product is not used as underlayment near the bottom of the eaves and upwards well past the outside walls. These little lakes, that get dammed up, will overflow water and as the water pours over the edge of the roof, the water freezes making these beautiful but dangerous icicles.

Icicles are formed from melted snow refreezing

Sue explained to me that the roofer told her, "I would never have icicles or ice dams again. And all of my house is covered with both, except the unheated garage. I’m being told it is because I don’t have enough insulation in my attic. I’m confused because I only have attic space in front of my house where I have no leaking!"

Another reason for the snow to melt is lack of ventilation. With a small gable end vent on the left side and most likely one on the opposite side. If there is no other exhaust venting in this attic and an equal amount of intake ventilation, the heated air just sits there and warms up the attic, melting the snow on the roof, instead of exiting the attic. I have even seen poorly vented dryer vents, that are terminated into the attic and not exiting out the roof. These can also heat up an area in the attic and cause the snow to melt.  A simple thing like this can go unseen unless an attic inspection is made.

The cures for this type of problem is to start with an inspection of the attic by a licensed roofing contractor.

1. Check the level of insulation.
2. Design a balanced attic ventilation system.
3. Ensure all heat sources are properly vented out of the attic.

These cures may not all ways fix the problem, especially in extreme conditions – but it will help get you started looking. Sue has an attic in the front of her home but vaulted ceilings in the rear portion of the home and our advice will not work in these areas and a more thorough inspection will be needed to solve this problem she is having.

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