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Masonry Wall Flashing - Critical to Performance, But Often Overlooked

Siegfried, Scott / Valentino, Erik

In modern masonry wall construction, with the prevalence of cavity wall systems and decreased redundancy, the wall system's ability to manage water is more important than ever. It is impossible to keep a wall watertight without the installation of proper flashing. For a cavity wall to perform correctly, the flashings must have provisions to manage water and rapidly expel it back to the exterior of the wall assembly through weeps. Flashing must also be able to preclude unintended lateral movement of liquid water through the use of end dams. The installation of proper flashing can be achieved, at a small percentage of the overall design and construction cost, if the designer provides good details and the contractor understands how the flashing is intended to work. Too often flashing is installed poorly or omitted altogether, allowing excessive water into the wall assembly. This results in accelerated corrosion of embedded steel members, deterioration of the masonry assembly and an increased potential for mold growth. Remedially addressing these issues requires costly and disruptive repairs. Using lessons from the restoration of existing buildings, these problematic issues will be reviewed and several key flashing areas will be discussed; including copings, through-wall, parapet rain screens, window lintels and sills, rising walls, and shelf angles. Examples of incorrect flashing and the resulting damage will be used to show the role flashing plays in maintaining a properly functioning exterior wall assembly, as well as successful remediation of the same details.