Volume 4, Number 1
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Founded in 1983, Kipcon is expert in building and site engineering disciplines, and specializes in providing engineering services relating to Community Associations.
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WATER INFILTRATION IN ROOFS
With winter upon us, the formation of ice and snow on our roofs has a tendency to accentuate any roof deficiencies that exist, both structurally and in terms of water infiltration. The three most common reasons for water infiltration are ice damming, inadequate or improper flashing and fire retardant treated plywood.
Ice Damming – Although ice damming in itself does not cause water infiltration, extended periods of ice damming can cause these problems. If there are deficiencies in the roofing or in the insulation of the roofing, ice damming can lead to a greater likelihood of water infiltration problems.
Ice damming generally occurs during periods of prolonged freezing temperatures, during which an accumulation of ice and snow exist on the roofs. Typically, this snow and ice is frozen solid at night but, during the daylight hours, due to a combination of the sun beating on the roof and the warmer air in the attic, the portion of the ice and snow that is bearing directly on the roof melts down into the gutters. As this moisture runs down into the gutters, since this area is colder than the upper roof surfaces, this moisture will have a tendency to freeze in the gutter and back up underneath the lower layer of shingles at the eave line. This phenomenon is known as ice damming. As the prolonged period of icing continues and this area of back up extends under the shingles, should there be any opening in the area where the sheathing meets the fascia board, this moisture can then extend into the attic space and cause water infiltration problems.
The ways to minimize the potential for water infiltration caused by ice damming include making sure that the joint between the fascia and the sheathing board is closed. If this is not the case, flashing can be installed to seal this opening. In addition, the insulation in the attic should be reviewed to make sure that it completely covers the entire ceiling surface of the living space below and the vapor barrier on the insulation is facing towards the warm surface. This will assure that the warm air from the living space below does not enter the attic and cause the ceiling of the attic to be warm enough to allow snow above to melt and run down into the gutters.
Should ice damming become a major source of water infiltration, the immediate short term way to resolve this problem is to remove the gutters in the areas where the water infiltration is occurring in order to allow the moisture to run directly off the roof and not back up from the gutters. In areas where this is an ongoing problem, heat tape is sometimes used at the lower area of the roof in order to keep this moisture from freezing and backing up. However, in most areas, ice damming is not a prevalent problem and only occurs in times of extended sub-freezing temperatures.
Inadequate or Improper Flashing – The primary weak spot in any roofing system occurs where there are intersections of roof planes with the vertical walls as well as the termination of roof planes. These are the areas in which flashing is installed to assure that no water infiltration occurs. In situations where snow and ice are sitting for extended periods, any weakness in this flashing system can cause water infiltration to occur. Once a leak in the roof is observed, it is not always easy to track down the exact location of the source of the moisture and, generally, the best way to resolve a problem such as this is to work with a reputable roofing firm to locate and correct the leak.
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