Damn Ice Dams.
While icicles hanging off of roofs or gutters might look beautiful, they are actually a sign of problems. Icicles typically mean an ice dam is nearby which spells trouble for homeowners.
What are ice dams?
Ice dams form when melting snow on a roof refreezes at the edge of the roof. The snow melts because of heat rising through the house, warming the roof to a temperature above 32° F. The melted snow then runs down the roof and re-freezes as it gets past the exterior wall and hits the uninsulated overhang of the roof creating an ice dam.
What causes ice dams?
Typically warm attic spaces occur because of inadequate ventilation through the attic, which is necessary to keep the roof deck cold. In addition to poor ventilation, the temperature in the attic is increased by lack of insulation in the ceiling, uninsulated recessed ceiling can lights, uninsulated attic stair openings, heating ducts and improperly vented bathroom fans.
Note: Vaulted spaces with foam insulation is a discussion for another time.
What damage can they cause?
Eventually, the ice dam will become tall enough that the melting snow will have no place to go except for under the shingles and into the exterior wall, ceiling or attic. Water infiltration into the interior of the house can cause warping and staining of drywall and paint, reduce the performance of insulation and create a damp environment which promotes the growth of mold. On the exterior, if an ice dam gets large enough, it can damage gutters and flashing.
How can they be prevented?
1. Properly ventilate the roof and attic.
2. Reduce or eliminate sources of heat into the attic, insulating around ductwork and sealing leaks around recessed can lights.
3. Increase the insulation in the attic floor.
4. Keep gutters and downspouts clean.
5. If you are building a new house or if you are having an existing house re-roofed, install an ice and water shield along the overhangs of the house. An ice and water shield is a self adhesive roofing membrane that is installed under the shingles and roofing felt to give an added layer of protection.
6. Contact a professional for help if you have major problems – roofers, HVAC contractors or architects are all good resources.
Pretty or not, icicles are unwanted guests in your home. While a future winter storm may seem like a long way off, now is the time to protect yourself against next year’s ice dams.
Note: Thanks to Kevin Vaught, at Larry L.Vaught Roofing for contributing to this article.