Which Diameter Fastener Should I Use for My Lateral Connection Design?

The yield modes for dowel-type fasteners are characterized by the dowel bearing/embedment strengths in the wood members, the bending yield strength of the fastener, or some combination of the two. With any connection, increasing the dowel bearing/penetration length of the fastener beyond a certain point will not increase the connection strength anymore, as plastic deformation of the fastener will occur prior to yielding of the whole contact area. Furthermore, it might not be advisable, for instance, to use a 1/4″ screw to fasten down a 9-ply CLT panel under high lateral loading when significantly higher capacities can be achieved with a 3/8″ or 1/2″ fastener. As a rule of thumb, maximum connection strength for a given fastener diameter will be achieved with a dowel bearing/penetration length of roughly 8d-12d (with d = outer thread diameter) in each of the members. Lateral connection design is an iterative procedure. The designer can begin with the rule of thumb mentioned above and adjust accordingly.