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What is Flashing?

Answer:
Flashing is a waterproof and non-reactive material

roofers use to protect seams and joints from rain damage caused by leaks. Flashing performs roughly the same job as caulking does for window and door frames. Roofing felt and shingles are often placed over flashing to direct rainwater away from the vulnerable seams between roofing elements.

Flashing can be made from a number of different materials, but thin sheets of metals such as aluminum, copper and galvanized steel are quite common. These non-reactive metals can be fashioned into strips of flashing on the building site itself and hauled up to the roof for installation. Some flashing is composed of polyvinyl chloride. A new form of flashing is composed of a tar-like substance with an adhesive backing material.

When different parts of a roof meet, there is often a seam line between them. This seam line will collect water if not sealed properly. This is why roofers use flashing to act as a sealant over the exposed seams. The flashing material is cut and bent to fit over these seams and is then nailed or screwed down to the roof itself. It is important that the individual pieces of flashing overlap in the direction of the water drainage. If the edge of a piece of flashing faces upstream and becomes bent outwards, the water could become trapped and make its way through the roof.

Once flashing is installed across all exposed roofing seams, other materials such as shingles or roofing tiles can be installed on top of it. Aluminum and copper flashing may be more expensive than PVC or galvanized steel to install, but they are also considered to be much more durable. The newer tar-like strips of flashing may be easier to install than metal flashing, and the material is chemically compatible with the other roofing adhesives and materials most roofers use.


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