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Finding The Source Of A Roof Leak

An example of a skylight that leaks
If you see or hear water inside your house during or after a heavy rain, then you probably have a leak in your roof. The problem is that the water can travel long distances inside the house before is visible. A leak in the shingles at the crown of roof can travel under the down the felt under the shingles until it reaches a weak point like a gap in the felt. The water then travels down the plywood until it reaches a gap in the wood. At this point the water may travel down the pitch of the roof along a rafter until is hits a nail head or wire where it drops on insulation. It may pool in the insulation until find a path out a light, vent, or down a wall. Here are some secrets to tracking down the source of the leak.

Look in the attic
Look in the attic during a hard rain. If you see or hear water dripping or see staining (wet wood), you will know the approximate location of the leak. Always try to follow the water path to the highest point.

Look in the atticInspect the high leak areas
For most roofs with adequate pitch, there are 2 main areas that start to leak well before the rest of the roof. These are valleys and flashed areas like chimneys, skylights, vent pipes and roof-mounted equipment. The large flat sections of a roof are rarely the source of leak unless there is a missing shingle. The water is moving quickly down these flat areas with nothing to change its direction so there is no reason for the water to pass the outer layer of shingles.

Look in the atticValleys
Many Roofs has valleys where two roof-sections intersect. These valleys are 10 times more likely to leak than a unobstructed section of roof. Not only do these area have much greater water flow than flat areas, they force the water to change direction. During heavy rains the water rushing down one section of the roof can force itself up under the single on the intersecting roof. When inspecting a roof, look for tears or puncture holes in the flashing along the valleys. If you traced the leak to a valley and you do not see a hole, then the water is entering the house under the singles.

Look in the atticFlashed Areas
Flashed areas like pipe vents, attic vents and fans are a common leak sources. These areas force the water to change direction so it naturally finds the fastest path to the ground (thru the house). The closer they are to the crown of the roof, the less chance they are the leak source. The amount and speed of the water increase as it travels down the roof so the lower parts of the roof are more likely to leak at a flashing point. Large flash points like skylights, chimneys, and swamp coolers are the biggest problem. These breaks in the roof usually have a wide area that totally blocks the water flow. The top of an average 24 inch wide skylight will force the water to pool above the skylight while the water travel horizontally along the top of the skylight. This area (above a skylight, chimney, and swamp cooler) of the roof is more like a swimming pool than a water slide so any defect in the installation can result in a leak. This area is probably the number source for roof leaks.

Once you find the source of the leak, you will need to repair the area. This can be done by a professional or buy the home owner.


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