Flashing (weatherproofing)

Flashing, in the context of weatherproofing, refers to thin, impervious materials used to prevent water penetration into a building's structure, particularly at junctions where different building materials or planes meet. It is a crucial component in maintaining a dry and structurally sound building envelope.

Flashing is most commonly made from metals like aluminum, copper, or galvanized steel, but can also be constructed from plastic, rubberized asphalt, or composite materials. The choice of material depends on factors such as cost, durability, compatibility with adjacent materials, and aesthetic considerations.

The primary function of flashing is to redirect water away from vulnerable areas, such as roof valleys, chimneys, wall intersections, around windows and doors, and over foundations. By creating a barrier, flashing prevents water from seeping into the building's interior, which can lead to problems like mold growth, rot, structural damage, and reduced energy efficiency.

Proper installation is essential for flashing to be effective. It requires careful detailing and precise placement to ensure that water is directed away from the building and does not become trapped behind the flashing itself. Common installation techniques include overlapping seams, soldering (for metal flashing), and the use of sealants to create a watertight seal. The type of flashing used and the specific installation method will vary depending on the specific location and the potential for water exposure.