There are many steps in the process of bringing lumber to the truss plant to be used in our trusses. Lumber must be harvested then sawn. Drying and planing brings the lumber closer to potential use, but it is not until the lumber makes it through the grading process that it is suitable for use. Sometimes the lumber is reviewed by inspectors to make sure visual inspecting and/or machinery is accurately qualifying the lumber. In the photo [See PDF or View in Full Issue], the lumber grader is remarking lumber that has been upgraded because the optical machinery judged some darkness in the lumber as knots larger than the grade allowed. With a visual re-inspection, the knots are within the upgrade and can be used appropriately. Is “Too bad the truss plant can’t upgrade lumber” what you are thinking now? “Where do I get one of these stamps?”
Am I right? Well, you cannot upgrade, but you can and should evaluate the lumber for suitability for your use in the truss at hand. Just because it meets lumber grades does not mean it meets your needs. There are several items that might make the lumber unsuitable while still qualifying for the grade as marked. Here are some of the issues we might run into on a regular basis.
- Wane that meets grade may be in a location that will impact connector installation and affect the required tooth count.
- Mill cuts, while allowed in grade, are not suitable for member applications, especially chords subject to bending forces.
- Crooks that meet grade for the length of the inspected lumber sometimes change when cut to shorter lengths. Cross cutting does not change the grade of the lumber once it’s initially graded, but it might change suitability due to the defect location in the shorter piece.
- Visual defects that meet grade might not meet your client’s criteria. Just because it meets grade does not mean it meets the impression the defect might imply. An example would be missing knots or holes in the lumber.
- Wedges are unique in that they usually need #3 lumber (sometimes #2); however, if the allowable wane in #3 just happens to be within the short length of the wedge, then the defect is not suitable and should not be used.
- Skips, places the planer did not hit the face or edge of the lumber, might make grade for the length, usually 1/16” on 10% in #1, or 1/8” on 5% in #2, or 10% heavy skips in #3; if the plated area ends up at the skip area, adequate plate embedment may not be achievable with roller equipment or certain hydraulic equipment.
- Decay is allowed in #2 lumber in the 2” dimension only, but it will not appeal to your customer.
These are a few of the most common examples, but there are many more situations that the lumber picker, catcher, and/or truss builder will need to evaluate. Ultimately, the fabricator is the responsible party. As the manufacturer of the truss, they carry the responsibility, so they are the supreme judge.
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