Roofing Icicles from gutter

Published on March 16th, 2017 | by Henri


Icicles on an unheated garage

Q.    I sent you an e-mail last year about the icicles hanging from my gutter on my attached garage which is unheated. There were also icicles on the gutter near the front door and above the back door from the heated laundry room. Your reply indicated that the icicles were forming due to the heat escape from the house.

In the fall we removed the gutter guards (white plastic with screening and another layer of plastic with 3/8″ diameter holes. We then cleaned whatever garbage was left in the gutters that the gutter guards did not filter out and left them uncovered for the winter.

Interestingly, this winter after heavy snow and below-freezing temperatures here in Illinois in December, nary an icicle had formed on these gutters. It appears that the gutter guards were the problem although I don’t know why. I wonder if this icicle problem occurs with any type of gutter guard. Thought you’d be interested to know what I discovered.

A.    Icicles form when the snow cover on a roof begins to melt, either from natural causes (warming temperatures or the sun’s action) or from an attic in which the temperature is above freezing.
In the case of icicles forming at your unheated garage, they are the result of natural causes.

As the melting snow travels toward the eaves and meets colder surfaces, it freezes and turns into icicles. If there are gutter covers, it freezes on top of them and continues outside the gutters.

If there are no gutter covers, the gutters and the downspouts fill up and icicles will form as the subsequent water overflows.

If you haven’t yet seen any icicles this winter, it is either likely that the conditions have not yet been met for their formation or that the gutters are not yet full of ice. Time will tell.

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