This article originally appeared on M. Stephen Doggett, PHD’s LinkedIn page. Is your wall screwed? Over 40% of all wall fasteners, including those used to fasten exterior insulation, are inherently inaccessible and untreatable. Water-Resistive Barriers (WRBs) address this issue with varying abilities to self-seal. But some WRBs, including wood-based integrated WRB panels, exhibit poor self-sealing, especially when penetrated by screws. Furthermore, rotational forces of screws cause shear stresses at the overlay-substrate interface, resulting in profound WRB distortion, overlay fracturing, and substrate uplifting. Here, I demonstrate examples of these effects using # 12 wood screws and # 14 self-drilling screws. The exposed wood substrate is now subject to water entry behind the WRB overlay – a condition that is similar to untreated fastener heads. Where compromised, the WRB no longer serves its intended role as a second layer of protection. Similar effects occur with many fastener-WRB interfaces. For example, loose, mechanically attached sheets tend to twist and wrap around the screw tip, causing fairly sizable rips and surface distortions. Anticipating these problems allows us to design around them. Considerations include: 1) thermally efficient drainage spaces; 2) WRB selection; 3) fastener selection; and 4) fastening methods.   About M. Steven Doggett, PHD We at Performance Pro Supply are big fans of the work of M. Steven Doggett, Ph.D., LEED AP.  The founder and Principal Scientist of Built Environments, Inc., Dr. Doggett has over 20 years of experience with environmental consulting, building forensics and building envelope design. Though his expertise centers on moisture control, he also regularly consults on hygrothermal (heated water) performance, indoor air quality, and improved building service life.