Anyone who lives in cold weather regions should take preventative measures to protect their home from the formation of ice dams.
Ice dams occur when roof gutters becomes clogged with ice and debris. As water from rain or melted snow runs off of the roof toward the gutter, it becomes trapped between the ice inside the gutter and the roof shingles. With nowhere for the water runoff to go, water can move back and underneath roof shingles. Once the water travels underneath the shingles, it may remain there for an extended period of time undergoing a long series of freeze/thaw cycles. Should water remain underneath the roof shingles, it won’t be long before the water begins to create roof deck damage and wood rot.
Fixing water damage as a result of ice dams is expensive.
Preventing ice dams is easy and inexpensive. Prevent ice dams during new construction or re-roofing by employing the following measures:
1. When installing a new roof, always install a good quality ice and water barrier on the first 3 feet of all roof eaves at minimum (or 2 feet past the first interior wall). Lower pitched roofs may require 6 feet of ice and water barrier or more. Minimum building code for most municipalities in Wisconsin require ice and water barrier to extend from the edge of any roof eave all the way up two (2) feet past the interior wall. In most situations, the roof soffit (overhang) is 1 foot or less wide. Therefore, standard ice and water barrier manufactured in three (3) foot wide rolls will meet minimum building code. This is why most roofers include one row (first three feet) of ice and water barrier in their bids for roofing work. If you have wider soffit, carefully read the minimum building code for roofing in your municipality and be prepared install more than one row of ice and water barrier. Also note that this is “minimum” building code. Generally speaking, more is better in this situation, but ice and water barrier is relatively expensive when compared to traditional tar paper underlayment. One must weigh the costs and benefits to going beyond the minimum building code in this situation.
2. Install gutters and downspouts large enough to handle all the water runoff from your roof. Most contractors will be able to calculate the necessary gutter capacity based on roof size. Larger roofs will require larger gutters with more water capacity. Custom seamless gutters are a bit more expensive than prefabricated gutters, but they pay for themselves once you consider durability and maintenance. Always make sure water has a clear path out of the downspouts and away from the foundation of the house.
3. Optimize roof ventilation by balancing intake vents (soffit or gable vents) and exhaust vents (ridge vent or box vent). There should be a 50/50 balance of cold air intake vents and warm air exhaust vents in the attic space directly underneath the roof deck. Cold air from the exterior enters the intake vents and pushes warm air out of the attic space through the exhaust vents in a properly functioning system. Without proper ventilation, warm air becomes trapped in the attic space. This warm air will warm the roof and melt any standing snow. At the same time, cold air outside can freeze the melting snow and create ice, and the freeze thaw cycle continues.
Ice dams on existing roofs can be prevented by following the steps below:
1. Maintain and clean your gutters and downspouts regularly. Make sure water can flow freely off and away from your roof. Once a downspout clogs and water freezes inside a gutter, it is too late! Installation of gutter guards is a good investment which will save you time and prevent clogs.
2. Install heated roof cables in areas where frequent ice damming occurs. Heated roof cables are readily available, low voltage heating elements attached to your roof eaves and gutters. These cables can prevent ice from forming in the first place.
3. Install extra insulation in attic spaces to ensure warm air from the house doesn’t escape into the attic and warm the roof.
4. Calculate the amount of roof ventilation that exists in the attic space. Add intake or exhaust vents if there is less than 1 square foot of vent area per 300 square feet of attic floor space. There should be a balance of 50% intake ventilation and 50% exhaust ventilation.
Preventing ice dams and the damage they will cause can be as easy as cleaning your gutters on a regular basis. If you can’t do it on your own or if you have areas of frequent ice damning, call a local, reputable roofing company for assistance.