Codes and industry standards require through-wall flashing to redirect and drain moisture. However, the mere presence of flashing does not mean that the wall cavity is adequately protected. Read on below to learn about the 5 most common issues with Thru-Wall Flashing and how they relate to moisture in brick walls.
Locating Defective Areas in Thru Wall Flashing
- Termination Seals Missing
- End Dams Missing
- Lap Seams Defective
- Flashing Does Not Extend to Daylight
- Ineffective Drainage or Weep Vents
Termination Seals Missing
Through wall flashing should be fully sealed to the air/moisture barrier at the vertical wall face. A sealed mechanical termination bar is often required. The chemical compatibility between the through wall flashing and the air/ moisture barrier should be evaluated. Without these seals, water can bypass the flashing entirely, contributing to problems like mold or moisture in brick walls.
End Dams Missing
Flashing can be very effective at collecting bulk water, however if this water drains to one side of the flashing and runs over the end, it can funnel water right back into the wall cavity. This is a critical failure point in brick wall flashing systems. Sealed end dams are required by the brick industry to ensure that all the water collected by the flashings is directed to the exterior face of the wall, helping avoid costly repairs tied to moisture in brick walls.
Lap Seams Defective
If the lap seams between sections of thru wall flashing are not sealed, water can penetrate directly through. Membrane flashing should be fully supported where it spans the brick wall flashing cavity to maintain a proper seal. Support is also required to prevent the flashing from sagging under the weight of water or mortar droppings.
Flashing Does Not Extend to Daylight
To effectively direct water to the exterior face of the wall, the through wall flashing must extend to daylight. Asphalt based flashing membranes should be held back from the exterior face of the wall to prevent asphalt leeching. These membranes require a metal drip edge to extend to the exterior face.
Ineffective Drainage or Weep Vents
Even properly installed brick wall flashing will fail if the drainage path is blocked. Weep vents are required in mortar joints to allow the flashing to drain. These vents must be set directly on the flashing. Weeps set above the mortar bed prevent the flashing from fully draining.
How To Manage Moisture In Brick Walls
Even simple assemblies will fail without proper installation. Paying close attention to the design and installation of through wall flashing is key to protecting your building from moisture intrusion. If you’re dealing with leaks or wondering how to manage moisture in a brick wall assembly, we would be happy to discuss a solution with you.
At Edwards & Company, we’ve been consulting on high performance building envelopes for over 30 years. Contact us if you have questions, and a member of our team will get back to you as soon as possible: