APA Updates Product Advisory – Flexible Sheathing Products Consistently Underperform in Independent Laboratory Testing

APA has issued an updated product advisory on flexible structural sheathing products, which combines three new products to the five previously tested from 2015 through 2018. As in previous rounds, these new tests were conducted by APA and the independent laboratories at Clemson University and the University of Oklahoma. Results from each lab show that all eight tested flexible structural sheathing materials overstate their lateral load resistances by as much as 42% when compared to their published design values.

Structural design properties for these flexible structural sheathings were evaluated according to two shear wall test standards listed in the manufacturer’s product evaluation reports ASTM E564, Standard Practice for Static Load Test for Shear Resistance of Framed Walls for Buildings, and ASTM E2126, Standard Test Methods for Cyclic (Reversed) Load Test for Shear Resistance of Vertical Elements of the Lateral Force Resisting Systems for Buildings, Method C (CUREe).

“Designers, code officials and the people who live or work in buildings expect the structural products used in them to comply with published design values,” said Dr. BJ Yeh, P.E., APA Director of Technical Services. “These test results raise questions about the safety and reliability for buildings constructed with these products.”

The Product Advisory: Performance of Flexible Structural Sheathing is available for download on APA’s website at www.apawood.org/resource-library.  

Detailed test reports are available to building officials and design engineers from APA upon request to helpdesk@apawood.org.

November 8, 2019