It's snowing in Bellingham!

Okay, it is not snowing right now. I admit it, I lied here at Active Rain. But with the hot weather in the Pacific Northwest, I wanted to give you a photo that would cool you down and be informative too. It is like having an ice cream. Last year, because of the heavy snow, we had the conditions that can lead to a problem that is more common in the cold northern climates: Ice dams. What are they? Well, simply, it starts when heavy snow collects on the roof. As long as everything stays frozen, all is well. But the problem comes in when heat escaping from the attic melts snow up above, and the melting water runs down to the colder eave areas and refreezes, forming a dam. That dam will keep other melting water from escaping so, in the case of sloped roofs designed to shed water (or any roof that is not designed to accomodate pooling water), some of that melting water might get under the roofing materials and that can lead to leaks inside the house, typically at ceilings or above windows at the eaves. For ice dams to form, conditions must be ideal, and a house that has never had such a problem might develop one if the snow fall and weather conditions are just right to stress some vulnerability of an otherwise working system. It has to do with how deep the snow is, how fast it melts and, at some homes, there might be an ice damn once every 20 years, despite there having been other years with significant snow. Good design can prevent ice dams, but that is often never thought about in climates where heavy snow is unusual. Some of the things they try to do include designing with shorter overhang at the eaves, providing adequate ventilation and heavier attic insulation, to reduce the heat loss from the home that melts the snow to begin with. If an ice damn potential does exist at a house, a few common means are used to prevent them, from simple to more complicated: adding electric heat cables at the eaves, upgrading insulation and ventilation, adding eave protection below or putting a modified bitumen "water shield" in the area where the water collects and penetrates -- in essence changing this vulnerable part of the roof to a surface that is no longer shedding style but more watertight, like a flat roof. This is a problem one does not expect to find in our maritime climate in the northwest, but every once in a while, a doozy of a snow storm can bring surprises. In the 2006 photo, notice the icicles from the melting snow.

Thanks for looking,

Steven L. Smith

Bellingham WA home inspector

www.kingofthehouse.com