Ice dams can cause roof leaks
Home Fix: Advice on tracking down a water leak and how to prevent ice dam problems and storm damage problems.
Scripps Howard News Service
Q: Last year I purchased what was advertised to be an energy-efficient home. The walls are concrete filled foam blocks and the attic has spray foam on the rafters. The energy bills are within reason for this type of home but I am experiencing a water leak on the ceilings near an outside wall. The contractor wants to check the roof as soon as the weather allows. If the attic side of the roof is covered with spray foam, how will he find the point of the roof leak?
A: One sure way to find the source of the roof leak is to use an infrared camera that can pinpoint the origin of the leak and might also reveal the path the water is taking to reach the ceiling or wall. If your contractor does not have this camera, the insulating contractor or a local home inspector may. Although roof leaks are common, I would not expect a new roof to leak unless there has been severe weather in your area.
What you may be experiencing is an "ice dam" problem. If the insulating contractor sprayed foam in your attic and stopped right at the outside wall at what is known as the top plate, then the overhang or soffit area of the home is not insulated. This portion of the roof overhang can receive warmth from outside conditions or through conduction from the portion of the rafters and roof decking that was not insulated. The foam insulation should have extended to the edge of the roof, covering all the exposed decking. Without insulation, the warmer area in and around the soffit allows the snow that is in contact with the roof to melt.
The melt water accumulates and becomes trapped by the snow pack near the edge of the roof. As the melt water refreezes, an ice dam forms that allows new melt water to pool on the roof. Roof shingles are water resistant, not waterproof, and the accumulating water can seep under the protective layer of shingles to reach the home's finished walls and ceilings.
To prevent ice dam problems or storm damage problems, I'm a firm believer in applying an ice and water shield product for all roof covering installations. Ice and water shield is a rubberized underlayment with a self-adhesive backing that adheres to the roof's decking. As the roof shingles are nailed in place, the rubberized ice and water shield will self-seal around the nail penetration preventing the possibility of leaks at these points. Even in severe weather when shingles could be damaged by strong winds, the ice and water shield will protect the home against leaks.
Ice and water shield can be applied for the first few courses of shingles, but I would prefer to see contactors use the shield to cover the entire roof area before any type of roof covering is installed. Although this application will add to the cost of the roof covering, having two layers of protection will ensure many years of protection from severe weather.
Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at d.Barnett@insightbb.com.
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