In cavity walls, water that gets past the brick runs down the back of the veneer. Through-wall flashing at the base, shelf angles, lintels and sills catches it, slopes it outward, and carries it past the face of the masonry, with weeps just above to let it out. It must turn up the backup wall, have sealed laps and end dams, and extend past the face with a drip.
Through-wall flashing stops a half inch short of the brick face, so water's just dumping back into the wall.
Flashing that ends behind the face of the brick looks neater and leaks; the drip edge has to sit out past the face.
Also heard as
- TWF
- thru-wall flashing
- cavity flashing
Related terms
Weep
An opening at the base of a wall or window system that lets collected water drain out.
End dam
An upturned end at the termination of a flashing that stops water from running off the end into the wall.
Mortar droppings
Mortar that falls into a masonry cavity during laying and piles up on the flashing, blocking drainage.
Flashing
Thin sheet metal or membrane installed at joints and interruptions in a wall or roof to direct water back outside.