A Guide To Roof Flashing

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Flashing, typically made of galvanized sheet metal so it doesn't rust, is an integral part of your roof. It can last longer than the shingles, so it isn't always replaced when you get a new roof. This longevity doesn't mean it can suffer damage, though, so it's important to understand how flashing works and when it needs to be replaced.  

What Does Flashing Do?

Where the shingles meet up with a new angle, whether it's caused by two roof planes coming together in a valley or the roof abutting up against a chimney, there will be a piece of flashing to seal the gap. The flashing's purpose is to create a water-tight seal between these gaps so that moisture doesn't seep under the shingles or into the attic. It also gives the roof a neat, finished look that is as attractive as it is useful.

Where Is It Located?

Flashing can be found where there is a seam on the roof. L-shaped metal flashing is installed around chimneys, rooftop HVAC units, skylights, and vents. Round rubber flashing boots can be found around circular penetrations, such as plumbing vent stacks. There may also be flashing running up the seam of a roof valley, which can be made of metal or asphalt shingle material. There is also a strip of water-shield flashing under the last course of shingles along the eave of the roof. 

How Do Leaks Form?

Leaks form when flashing or the sealants that hold it in place begin to fail. Often it is the sealant that gives out first. Exposure and age cause it to develop cracks or begin to peel up. Moisture can work underneath via these damage points, further weakening the seal. Then, the wind comes and the now weakly sealed-in-place flashing becomes warped so that water can easily flow beneath it. Old age can also wear down the flashing. The metal may begin to corrode, or rubber boots may start to crack. 

Is a Full Roof Replacement Necessary?

Fortunately, it's not usually necessary to replace the whole roof if only the flashing has damage. Only the shingles around the damaged area will need to be removed. Then the old flashing is replaced with a new piece, which is sealed in place. Your roofer will then replace the shingles that had to come off. If there was a leak, some repairs to the underlying roof decking may also be needed before new flashing and shingles can be fitted.

Contact a roof repair contractor for more help with your flashing repairs.