What is the Best Way to Handle Defects Under the Plated Area?

Everyone who uses lumber in trusses understands that defects in lumber can impact truss performance in different ways. Some defects are not important but others will affect truss performance and can even cause truss failure. [For all photos, See PDF or View in Full Issue.]

In the first photo, the result of using a heavily waned floor truss web has yielded a serious manufacturing non-conformance that most likely would have resulted in failure.

This truss was designed as a girder truss and once installed would carry multiple trusses and very high concentrated loads. Fortunately, an inspection caught this truss before it was shipped.

In the second photo, a roof truss was on the table getting ready to be pressed. Most of the area under the connector was wane. The result would have been a significant loss of tooth count.

The decision to use a web or replace the lumber needs to be made quickly and often. Without specific guidance, several things could happen, including

• Trusses are built with non-conformances that can result in failure, create call backs, and even cost you customers.
• Truss builders decide to cull any lumber with defects, resulting in a significant loss of profit due to the high cost of goods.

When properly trained, truss builders will make good decisions regarding wane. They will understand when to cull lumber and when to upsize the connector, which will reduce risk, maximize profits, streamline operations, and eliminate additional work.

Things to Consider

1. Although solutions depend greatly on fabrication tolerances used to specify the connector, these general rules can be used and adjusted based on your plant situation.
2. If the wane in the connector area is 1/3 to 1/2 of the face, then upsizing the connector to make up for loss of tooth count may be all that is necessary.
3. Decisions are dependent on software settings, but it is normally a good assumption to set fabrication tolerances at 10% or higher.
4. If the wane in the connector area is less than 1/3 of the face, then fabrication tolerances set at 10% would not normally require upsizing the connector.
5. If the wane in the connector area is 1/2 or more of the face, regardless of the plate tolerance the lumber should be culled.
6. The cost of replacing lumber is generally much higher than upsizing the connector, but if the lumber is deficient then upsizing the plate has little impact or improvement.
7. You should validate your methodology by reviewing your selections using the plate placement method or counting the required teeth.
8. Replacing floor truss chords can have a significant impact on material cost.
9. Balancing the cost of upsizing the connector versus replacing the lumber is key to guiding your truss builders.

The final photo is a good example of 50% wane. What would you do?

An ANSI/TPI 1 3rd Party Quality Assurance Authorized Agent covering the Southeastern United States, Glenn Traylor is an independent consultant with almost four decades of experience in the structural building components industry. Glenn serves as a trainer-evaluator-auditor covering sales, design, PM, QA, customer service, and production elements of the truss industry. He also provides project management specifically pertaining to structural building components, including on-site inspections and ANSI/TPI 1 compliance assessments. Glenn provides new plant and retrofit designs, equipment evaluations, ROI, capacity analysis, and CPM analysis.