What Is Flashing for Siding?

Eaves

• The eaves of a home are where the roof terminates into the wall. As a general rule, they carry on out past the walls of the building by a short distance to help keep any water from draining off the roof and onto the wall, and when guttering is used are fairly successful. However, flashing is still an important element of the siding at the uppermost part of the wall where it meets the eaves, as it wraps the joint between wall and roof and keeps any residual moisture from penetrating.

Windows

• On window installations, the siding generally covers whatever flashing is installed around the window. The flashing at this point is meant to cover the seams of the window frame so that any condensation is forced away from the window and down into the waterproof layer behind the siding. However, some flashing protocols are actually installed on top of the siding as well. In either case, the goal of the siding flashing here is to keep water from going through the window and damaging the internal structure of the home.

Ledger

• The part of the wall where the exterior section meets the foundation or any decks and patios is known as a ledger. If flashing isn’t provided at this point, any water that has drained down the wall on top of the siding will find a place to penetrate beneath the siding and thus the wood behind, beginning the rotting and molding process. Flashing is bent over the ledger board section under the siding to keep water from having the opportunity to soak in, instead forcing it to drain out into the ground.

Siding

• While not all types of siding require flashing in between the rows of siding, some do. For example, lap siding generally is installed with top pieces overlapping the bottom pieces so the water is always forced to drain outward and down. Panel siding, on the other hand, is installed flush with the pieces surrounding, and there needs to be a flashing element installed along the horizontal seams. Z-flashing is most commonly used at these points.