Metal roof flashing
Roof flashing is the installation of a thin metal sheet on roofs with the purpose of redirecting flow-water away from chimneys, roof joints and walls. Flashing can be installed like shingles, with one piece lapping another, or it can be sealed to function as one continuous surface. Either way, flashing can also be reconfigured with a non-continuous profile to prevent water from entering via surface tension.
Flashing can be made of several different types of materials, from plastic and rubberized asphalt to a variety of metals. It can be exposed or concealed. Metal flashing is typically exposed but can be installed under the shingles or outer covering. Roof flashing is used around projections or discontinuities of, what else? The roof. Its main job is to deflect water away from the seams or joints and in roof valleys where water runoff is concentrated. Roof penetration flashing is for water-proofing places where pipes, supports, cables, and other roof protrusions are built.
Channel flashing is specialized roof flashing shaped like a “U” or a channel to catch water at the edges of a tile roof where it meets the wall. A drip edge performs a similar purpose. Another design for roof edges is called kick-out flashing. It is installed at the bottom of a roof and wall intersection, with the lowermost portion formed to deflect water away from the wall. Valley flashing is to protect the valley where two roof planes intersect, rather like channel flashing. Wall flashing serves the same purpose as roof flashing and can be directly embedded into a wall to direct any water that gets in right back outside. It’s used at windows, areas of structural support, and other interruptions in the wall. It operates by directing water toward weep holes.