Through-wall flashing, end dams and weeps · Lesson 1 of 4

Through-wall flashing, end dams and weeps: principles and terminology

What through-wall flashing does in a drainage wall, where it goes, how it reaches and passes the face, what end dams and weeps are for, AFS's Through Wall template, and the OSHA zone around a wall being built.

You will be able to: Name the parts of a through-wall flashing assembly, say where it goes, define end dam, weep and drip, and state the safety boundary for working beside a masonry wall under construction.

10 min · 10 slides · 7 questions

All lessons in this module

Slide 1 of 10

What through-wall flashing does

BIA defines through-wall flashing as an impervious material in a masonry wall that contains water which has got past the outer wythe and sends it back to the exterior.

It is required in a drainage wall and recommended in a barrier wall, as a second line of defense.

Sources

Technical Notes on Brick Construction 7: Water Penetration Resistance - Design and Detailing (2017) - Brick Industry Association (Brick Institute of America)

Glossary

Through-wall flashing: An impervious sheet, of metal, membrane or a composite, installed across a masonry wall to contain water that has got past the outer wythe and send it back to the exterior.
Drainage wall: A masonry wall with an air space behind the outer wythe, such as a cavity wall or anchored veneer, built so water that gets in runs down the air space, onto the flashing and out through the weeps.
End dam: The turned-up end of a through-wall flashing where it stops, so the water it collects cannot run off the end into the wall. BIA asks for it to turn up into the head joint at least 1 in.
Weep: An opening in the outer masonry, immediately above the flashing, that lets water collected on the flashing out of the wall. BIA prefers the open head joint, formed by leaving mortar out of a head joint.
Drip: The projecting edge of a flashing, formed past the wall face so moisture exits the wall and is directed away from the face below.
Limited access zone: Under OSHA 29 CFR 1926.706(a), the area along a masonry wall under construction, equal to the wall height plus four feet and as long as the wall, that only employees building the wall may enter.