The Ice Dam Cometh

Many homeowners in the northern regions have experienced a winter storm condition called ice damming. Ice dams occur when a sequence of weather conditions occur within a brief time frame. Conditions for ice damming usually only occur every five to seven years, but 3 out of the last 7 winters in the Chicago area have fueled such conditions.

What Is An Ice Dam?

Ice dams are formed when the gutter system becomes filled with moisture which when frozen forms a “dam” at the eaves of the roof. When additional moisture gathers on the roof and is not able to run off due to the “dam” at the gutter line, this moisture becomes a frozen layer on the roof surface and may back-up towards the peak of the roof.

What Causes My Home To Leak?

Ice dam related leaks occur when warm, heated air from the building migrates through the roof deck and warms the underside of the roof. With outside temperatures keeping the top outside layer of moisture frozen the warm deck/roof melts the bottom layer of ice returning it to a liquid state. This underlayer of water will run down the shingles until it meets the dam at the gutter line. With no escape route, the water pools, then backs-up underneath the shingles and enters the attic area through nail holes and seams in the roof deck.

As water begins to penetrate sheathing, insulation, wall cavities, and sheetrock or plaster:

• paint can begin peeling on both inside and outside walls
• roof coverings, fascia and gutters can be damaged
• structural damage can result from the weight of the ice dam

Why Does My Roof Not Keep The Water Out?

Shingle roof systems are designed to channel water from the high points of the roof to the lower sections where it should exit the roof either into the gutter system or simply onto the ground. Shingle roof systems are not designed to hold water or prevent water from entering that runs or is blown uphill.

This is not a design flaw with the roof system or an indication of a poorly installed roof. Ice dams are winter storm conditions, which prevent the shingle roof system from shedding water as designed.

In our next article, Ice Dam Leaks & Prevention, we will delve a little deeper into this issue.

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