What about structural strength?
While overdriven fasteners are not detrimental to water control when the cladding is drained and back vented, it is indeed true that overdriving fasteners affects structural performance. This is especially true if the problem is pervasive.
Per a 2016 research report from the Structural Building Components Association (SBCA), if 100 percent of the fasteners are overdriven to 1/16”, the resulting reduction in shear strength is about 9 percent, if all of the fasteners are overdriven to 1/8”, the reduction in shear is about 17 percent, and if all of the fasteners are overdriven to 3/16”, the reduction in shear strength is about 25 percent.
Obviously it’s unlikely that all of the fasteners on any given project would be overdriven, and all by the same amount. The report includes a chart showing a number of scenarios yielding reductions in shear strength that range from less than 1 percent to 25 percent.
Structurally speaking, overdriving fasteners can indeed be very serious -- especially if the issue is pervasive -- but it is not the case that overdriving the fasteners is akin to reducing the overall thickness of the panel, which is to say that overdriving any given fastener does not turn a 5/8” panel into a 1/2” panel. Overdriving the fastener affects the fastener, not the stiffness of the panel overall.
It is also important to remember that the fastener installation is not the only factor affecting structural strength. How close fasteners are to the edge of the panel matters a great deal more than whether or not they are overdriven. The same is true of panel dimensions and orientation on the wall (vertical or horizontal).
This brings us back to where we started: building performance is complicated! And no manufacturer can sell you a product that obviates the need for competent design and attentive installation.
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Per a 2016 research report from the Structural Building Components Association (SBCA), if 100 percent of the fasteners are overdriven to 1/16”, the resulting reduction in shear strength is about 9 percent, if all of the fasteners are overdriven to 1/8”, the reduction in shear is about 17 percent, and if all of the fasteners are overdriven to 3/16”, the reduction in shear strength is about 25 percent.
Obviously it’s unlikely that all of the fasteners on any given project would be overdriven, and all by the same amount. The report includes a chart showing a number of scenarios yielding reductions in shear strength that range from less than 1 percent to 25 percent.
Structurally speaking, overdriving fasteners can indeed be very serious -- especially if the issue is pervasive -- but it is not the case that overdriving the fasteners is akin to reducing the overall thickness of the panel, which is to say that overdriving any given fastener does not turn a 5/8” panel into a 1/2” panel. Overdriving the fastener affects the fastener, not the stiffness of the panel overall.
It is also important to remember that the fastener installation is not the only factor affecting structural strength. How close fasteners are to the edge of the panel matters a great deal more than whether or not they are overdriven. The same is true of panel dimensions and orientation on the wall (vertical or horizontal).
This brings us back to where we started: building performance is complicated! And no manufacturer can sell you a product that obviates the need for competent design and attentive installation.
Next: About me