It’s true that, by nature, the materials currently used for wood trusses can vary in strength and properties. Given a specific lumber size and grade, truss builders often need to evaluate lumber picked, cut, and provided to build the specific job at hand. After verifying the lumber grade, the next step is to qualify the member’s ability to serve the task at hand. Because of this, some training and education is required for the most effective builder. Truss builders need some understanding of properties and characteristics of lumber so they can identify defects and situations that could impact performance, otherwise near perfect lumber properties will be required.
In the photo example, the k web shown has extensive wane in the plated area. Upon inspection, the builders used the connector as specified. However, the plate sized by the truss designer required a joint stress index of 90%, meaning that a significant amount of the available connector is required, allowing for little defects. In fact, this situation would not have improved had the builders upsized the plate one or two sizes because of excessive wane.
The general conclusion is: if we want to utilize marginal material, then design information will be required for the truss builder. Most design software has a provision to print this info. The second (unrelated to the truss photo) is an example of what is possible. This detail provides accurate, exact positioning and available tooth count verses minimum required tooth count shown as a fraction. Providing this detail to the table will enable builders to see joint requirements, thereby allowing them to make sound decisions when utilizing less than perfect lumber.