A THIN STRIP
Flashing is a thin strip or layer of waterproof material that prevents water getting in where it shouldn’t. You will find flashing on the exterior of your home around windows and doors, along the tops of foundation walls and chimneys, and at roof intersections. Flashing helps keep the water moving away from the house at points where it changes direction.
Flashing has to be large enough to prevent any water intrusion that can cause damage and rotting. Even in driving rain, the water should move up the flashing and then back down without ever going behind it. The flashing should fit snugly to provide a good watertight seal.
If you install a dryer vent or an exhaust fan or anything that puts a hole in your exterior wall, this can compromise the drainage plane. These holes must be flashed correctly to keep water out. You could otherwise end up with a leak that goes undetected for months until one day you wake up to serious water damage and mold inside the house.
Flashing should always be directed downwards away from the wood framing towards more flashing or the next layer of the drainage plane.
WATCH THE WATER FLOW
To check whether your flashing has been installed properly, watch how rainwater flows down the side of your house. It should flow freely all the way down without encountering an open seam, a hole or lip that stops its progress.
CAULKING IS NOT ENOUGH
Caulking breaks down over time and shouldn’t be relied on as the only way to seal around an opening. The flashing on its own should be able to protect the house from any water penetration before the caulk is applied.
WHAT IS IT MADE OF?
Flashing is usually made from aluminum, copper, steel or PVC. All these materials come in rolls of different widths that can be cut and bent into shape at the job site.