What is an ice dam?
An ice dam occurs when a ridge of ice forms at the edge of a roof (roof eave) and prevents melted snow (water) from draining off the roof. The water that backs up behind the dam can intrudes under the shingles, penetrate the underlayment and deck sheathing. It then saturates the attic insulation and ceiling drywall. You may discover water droplets on the ceiling which also present as a large round water stain.
What Causes Ice Dams?
There is a complex interaction among the amount of heat loss from a house, snow cover, and outside temperatures that leads to ice dam formation. For ice dams to form there must be snow on the roof, and, at the same time, higher portions of the roof's outside surface must be above 32°F while lower surfaces are below 32°F. For a portion of the roof to be below 32°F, outside temperatures must also be below 32°F. When we say temperatures above or below 32°F, we are talking about average temperature over sustained periods of time. The snow on a roof surface that is above 32°F will melt. As water flows down the roof it reaches the portion of the roof that is below 32°F and freezes which causes an ice dam.The dam grows as it is fed by the melting snow above it, but it will limit itself to the portions of the roof that are on the average below 32°F. So the water above backs up behind the ice dam and remains a liquid. This water finds cracks and openings in the exterior roof covering and flows into the attic space. From the attic it could flow into exterior walls or through the ceiling insulation and stain the ceiling finish. The top surface of the insulation is warmer than the other surroundings in the attic. Therefore, the air just above the insulation is heated and rises, carrying heat by convection to the roof. The higher temperatures in the insulation's top surface compared to the roof sheathing transfers heat outward by radiation. These two modes of heat transfer can be reduced by adding insulation. This will make the top surface temperature of the insulation closer to surrounding attic temperatures directly affecting convection and radiation from this surface.
What Can I Do?
Ice damming can be expensive to mitigate. It may be covered by your home owner insurance. Most all of this damage requires water extraction and drying by a professional. Remediation is imperative to avoid mold. Time is of the essence. Skyline Consulting Group, LLC works with you and will advise on the best way to approach the problem. We are state licensed.
First, make the ceiling air-tight so no warm, moist air can flow from the house into the attic space. After sealing air leakage paths between the house and attic space, consider increasing the ceiling/roof insulation to cut down on heat loss by conduction. Both of these actions will increase the snow load that your roof has to carry because it will no longer melt. Can your roof carry the additional load? If it is built to current codes, there should not be a structural problem. Roofs, like the rest of the home, should have been designed to withstand expected snow loads. Natural roof ventilation can help maintain uniform roof temperatures, but if the long-term actions described here are done effectively, then only small amounts of roof ventilation are needed to maintain uniform roof surface temperatures. If heat transfer has been reduced substantially, then snow will build up on the roof and cover natural roof ventilation systems, reducing attic ventilation rates. Natural attic ventilation systems are needed to dry the attic space and remove heat buildup during the summer. Mechanical attic ventilation IS NOT a recommended solution to ice dams. It can create other attic moisture problems and may cause undesirable negative pressure in the home. We at Skyline Consulting Group, LLC, have a variety of products, means and methods to stop ice dams from occurring and damaging your home, avoiding and mitigating mold infiltration and water damage and repairing all damage that has occurred. We are a General Contractor. We handle all aspects of your project without your having to deal with multiple contractors. If you’re in the NJ/Southern NY State areas and you need assistance repairing damage from and avoiding ice dams, NOW IS THE TIME TO CORRECT THE PROBLEM…not in the middle of winter! CALL SKYLINE CONSULTING GROUP, LLC for a free survey and estimate today.