A roof valley is very prone to leaks, especially if you have an older roof. The reason why the roof valley is such a sensitive area has to do with all the rainwater and/or melting snow that accumulates and flows through the valley on its way into the gutters.
Roof leaks are also very common in the winter, when all the snow accumulating on a roof creates a potential for a roof leak to develop, especially if a roof valley on your property is not properly flashed.
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There are many factors that can contribute towards a failure of a roof valley flashing; structural issues, inadequate construction, improper roofing methods and material deterioration.
Common Causes of Roof Valley Leaks
- Missing Ice & Water Shield. A properly flashed roof valley should have an ice and water shield installed, with roofing felt being properly secured over the ice and water. If the ice and water shield is missing, then you will have to remove the shingles on both sides along the valley, put ice and water shield in place and re-shingle the roof. You can check to see if the ice and water shield is installed by going into your attic and checking for it through the spaces in the boards, if there are any spaces where the roof valley is located (You will not be able to see much if you have plywood for a roof deck). You can also put up a ladder towards the valley on your roof, lift up a few shingles and check to see if the ice and water is in place. If it is missing, then you will have to make sure it gets put in place. If you have multiple valleys on your home, you may have to consider a complete re-roofing job, especially if your roof is rather old, and will need to be replaced soon.
- Aging shingles in a roof valley areas create fissures and cracks that permit moisture to pass through. Intact shingles create a water barrier in a new or a well-maintained older roof. Exposure to sun, wind, rain and snow gradually cause shingles to dry out, shrink and break apart. Eventually pieces of roofing shingles may actually blow or be washed off the roof. When this happens, the underlying roofing materials get exposed, and leakage become a very real possibility and a very costly potential problem.
- Improperly placed roofing nails during roof valley shingling/installation can accelerate the shingle aging process. When roofing nails are placed within the seam areas of the roof valley they can draw moisture through. Tension also is created in shingles when they are nailed too close to the roof valleys and this stress results in premature wear and cracking, causing speedy aging of and failure of the shingles. Roofing nails instead should be a minimum of six to ten inches away from the seam to reduce the pressure on the roofing materials.
- High winds sometimes blow shingles away from the roof valley particularly if the edges of the shingles are not nailed in place because of shingle strain, described above. Cut roof valleys also can easily be dislodged because of rain and wind. Damage to the roof and interior can by minimized or eliminated if a homeowner replaces the affected materials quickly.
- Roof valleys collect dirt, leaves, tree branches and limbs, snow and ice. The natural downward flow of water is interrupted when these foreign objects pile up, and water will pool and become trapped, ultimately seeping through. To avoid this build-up, inspect your roof a minimum of two times per year. Removal of debris collecting in the valleys and gutters will allow water to quickly drain away, and protect shingles and flashing.
- Sometimes an older home's roof is more prone to leaking in the roof valleys because of old repairs. The sealants and roof pitch used can crack and chip away over time. If your roof valley leak is an old repair gone bad, consider having a professional repair the leak properly. Some shingles and flashing may need to be removed and replaced, but the roof can usually be saved with a good-quality repair.
As a temporary measure, you may be able to apply some roof sealant and roof cement to flash out the source of a leak provided that you can locate it, without removing all the shingles around the valley. It may be possible to do it, but it will likely be only a temporary measure that will work only for a short period of time. Eventually, you will need to remove all the shingles from around the valley, install ice and water shield, underlayment, and properly re-shingle the roof.
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