Do Gutters Cause Ice Dams?

Wednesday, February 6, 2013 2:27:00 PM

Gutters and Ice Dams

One question that is often posed by homeowners is "Can I just take my gutters off to prevent ice dams?" The reasoning goes like this. The snow melts on the roof, runs down to the gutter, and refreezes there. If there is no gutter, the ice cannot form because there is no place for the melt water to refreeze. Simple enough - no gutter, no ice dam. Well, it may not be that easy. It is true that snow on the roof is the biggest contributor to ice dams. Also necessary is something to melt the snow. That most often is heat loss from the house itself. Other contributors are temperatures fluctuating above and below freezing and solar radiation. 

Homes without gutters can have ice dams.

As can be seen in the picture to the right, an ice dam and icicle formation has formed even though this house does notNo Gutters on house ice dam forms have gutters. Even with the relatively light amount of snow, the icicles and ice dams are beginning to form on the eave edge. Why is this? When the melt water reaches the "daylight", or exits the insulating insulating effect of the snow on the roof, it has a chance to refreeze. So it is the insulating value of the snow that keeps the melted snow liquid. Once it reaches the edge of the roof, it is cooled very quickly and refreezes into icicles and ice dams. Some claim the entire eave is the cold area. While the eave is not technically over the heated area of the house, the temperature on the surface of the roof is not significantly colder there. Again, snow is an insulator. It is when the melt water reaches the edge that it is exposed to more frigid temperatures and has a chance to refreeze and form an ice dam. So, whether there is a gutter or not, it is all about the edge. Keep the edge clear - no ice dams. Keep the gutter clear of ice - no ice dams.

Ice dams and complex roof structuresComplex roof designs lead to roof ice dam formation.

Another contributing factor to ice dams forming on roofs is related to architecture. Complex roof designs often funnel rain and melt water to small areas. As can be seen in the picture to the left, a large portion of the upper roof drains to a small section of eave. That eave also has a valley that funnels water into the same location. So, even with proper air sealing, insulation, and ventilation, the complex roof design often results in ice dam formation. This residence is in Chenequa, WI. We drive by it often and it is the same every year. On the above picture, the valley ice dam builds very large. There are skylights in the roof below. It is only a matter of time until those skylights sustain damage from the falling ice. We installed an ice dam prevention system on a large commercial property that sustained damage when ice falling from an upper roof crashed through the lower skylight roof.

Are gutters necessary for a proper ice dam prevention system to function?

Gutters do have their place in Wisconsin construction. They properly drain water away from the house preventing foundation leaks and damage to the siding and landscaping. Water dripping from upper roofs can significantly shorten the lifespan of the shingles below. So, it is good practice to install gutters. With a roof ice dam prevention system, the gutters play an important role as well. Melt water is properly channeled to the ground below. When melt water is allowed to freely drip, it can spread out further than the area warmed by the roof ice melt system. Gutters and downspouts eliminate this dripping and direct the melt water to the areas protected by the heat cable system.

Whether you have gutters or not, we can assist you in the proper design of your ice dam prevention system. Our approach is straightforward and effective. We do not use hardware store heat cables in any of our designs. Our UL listed heat cables form the back bone of our systems. When you are ready for a professionally designed, contact us to set up an in home consultation.