How to minimize the impact of ice dams
The winter problem of ice dams is common in many areas of the country where snow fall and frequent periods of thawing and refreezing result in water from melting snow freezing as it reaches the roof eaves.
There, because the eves can be colder than the roof due to inadequate roof insulation or poor attic ventilation – or just because of an unrelenting thaw and freeze cycle – ice builds up and long icicles form.
This creates a significant load on the roof and can cause extensive damage as the build up of ice traps water from melting snow on the roof.
Shingles are designed to make water run off, but if water is trapped, it can get between the shingles and damage roof sheathing or leak through the roof and damage ceilings, walls, rafters and trusses. Water in the attic or other enclosed interior areas can lead to mold when warmer weather arrives. Here is how to minimize the impact of ice dams and reduce the damage.
Minimizing damage from ice dams
When roofing in areas with regular freeze/thaw cycles, use a moisture barrier between the sheathing and the roof covering. A self-adhesive rubberized underlayment will provide the needed protection because it will close around the roofing nails as the shingles are attached.
Underlayment is also a wise choice in areas that don’t see snow, because sun-damaged or wind-blown shingles can allow water to infiltrate and damage the sheathing if it’s not protected.
If a roof has been installed without a moisture barrier, the lower courses of shingles can be carefully lifted and a band of rubberized self-adhesive sheeting can be applied in areas where ice dams are most likely to form.
The added cost of moisture barrier when you install a roof will be far outweighed by the potential cost of repairing damage to roofs and interiors damaged by water.
For areas of the country that see major snowfalls, there are products that can be applied to the roof edges to heat the roof. This usually takes the form of a 12-watt commercial-grade, self-regulating heat cable or a mesh.
While these do help to melt ice before it can result in dams, if they are laid on the roof surface much of the heat just escapes into the air. If you are installing a heating system on the roof, it will be far more effective if you install it between the moisture barrier and roofing.
—By Steve Sturgess, stevesturgess.com