Flashing is a material, usually aluminum or galvanized steel that is used over joints in roof and wall construction to prevent water seeping in and causing damage. Depending on the style of your house’s roof, you probably have it in the valleys, around the chimney and pipes, and around any dormer windows or skylights. Most damage shows up either in flashing that’s deteriorating due to weathering and oxidizing, or in flashing that has come loose.
Flashing is a small, cheap but highly critical point in your roofing system.
It’s here, at all the flashing points that most leaks occur.
Small pieces of metal are bent & slipped between each course of shingles when up against a cheek wall of a dormer, or a longer piece bent and laid across the front of a dormer.
Lead flashing is laid in the bricks of a chimney & interwoven between shingles, and all for the express purpose of directing the water down the roof and not allowing it to seep in anywhere.
All of this is done at the critical points in a roofing system, where the roof meets another object, that being a dormer, a wall, a chimney or a valley within the roof itself.
Leaks never really occur within the open field of a roof, but nearly always occur at these critical junctions, and sadly, almost always, it’s because someone didn’t know how to use & install a simple cheap little piece of metal at a critical point in the roof.
where the roof meets a wall ,chimney vertical surface
Flashing is need when any roof surface meets another surface. This would even be where another roof surface meets another roof surface or even the edge of the roof. Other examples would be gutter flashing (gutter apron) and even the edge of the roof (drip edge or d-style). Any where there is extrusions in the roof surface of any type, there should be some sort of (boot) flashing, (Chimney) flashing or skylights (Deck mount or curb mount) flashing . Final example would be where roof meets a wall would need (step) flashing. There are basically about a dozen different material need to construct a proper roof and 10 of those materials would be considered flashing… 