ClarkDietrich is pleased to announce that its BackerBead vinyl accessory product has passed testing under ASTM E-331 Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference. This test method determines the resistance to water penetration for exterior windows, curtain walls, skylights, and doors when applied under uniform static air pressure differences.


BackerBead is a labor-saving component for stucco and thin stone applications that provides protection against moisture penetration around door and window openings. The combination bead features a factory-applied backer rod that is affixed to the vinyl casing bead that allows the installer to create the necessary gap on the wall without the hassle of aligning it in the field, thereby saving time and materials.


The test is a real-world simulation that compared the use of no backer-rod/casing bead in terminating a stucco system around a window opening versus the same stucco assembly with the ClarkDietrich BackerBead. In side-by-side tests, the BackerBead system with sealant passed the E-331 water-penetration test, simulating air pressure of a 50 mph wind/rain. Conversely, the stucco system terminated with no isolated jointing failed in less than 15 minutes.


“This test data demonstrates that the use of a backer-rod/casing bead with proper sealant provides the best opportunity for isolating dissimilar surfaces in both residential and commercial applications,” said Christopher Little, Senior Product Manager, ClarkDietrich. “The real-world performance of BackerBead has shown time and time again to withstand the rigors of the jobsite and provide the highest level of moisture protection once installed.”


Tests were performed by Fenestration Testing Laboratory in Miami, Florida in April, 2018.  A copy of the results are available upon requests from Clarkdietrich at


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