Our industry design standard, ANSI/TPI 1, regulates numerous elements in constructing roof and floor trusses. The following is a brief non-exhaustive summary:
- Lumber grades and moisture content
- Pedigree of lumber grades and lumber management
- Controls on truss profiles
- Verification of plate size, gauge, and type
- Plate embedment requirements
- Plate placement
- Gaps between connected members
- Detection of defects within plated areas, along with other potentially harmful flaws
- Rotation of plates.
Among these nine items, the rotation of the connector—and potentially the location of the plate—exerts a significant influence on design that is frequently underestimated. [For all images, See PDF or View in Full Issue.]
The Critical Role of Truss Plate Placement and Tooth Orientation
In the world of engineered wood trusses, the placement of metal connector plates at joints is far more than a manufacturing detail—it is a structural necessity. Proper plate positioning ensures that loads are transferred efficiently and that the truss performs as intended under design conditions. Quality Control (QC) factors such as plate offsets, embedment depth, and alignment are essential to meeting ANSI/TPI 1 standards. Shown in the image is Figure 5.3-2 from Chapter 5.
Equally important, yet often overlooked, is the orientation of the plate teeth relative to the lumber grain. This relationship directly influences joint capacity and lateral resistance. Industry standards define four key conditions for plate and grain alignment:
- AA: Plate parallel to load, grain parallel to load
- EA: Plate perpendicular to load, grain parallel to load
- AE: Plate parallel to load, grain perpendicular to load
- EE: Plate perpendicular to load, grain perpendicular to load.
Understanding these orientations is critical for ensuring structural performance and avoiding costly errors.
Plate Placement Practices in Truss Plants
Modern truss manufacturing facilities commonly utilize automated presses and advanced quality control systems, such as SBCA’s Digital QC, to ensure accurate plate placement. However, technological solutions are not a substitute for diligent oversight. It is essential to consider whether regular manual inspections are conducted and whether fabrication teams fully understand the importance of correct plate orientation.
While shop drawings typically provide clear direction on the orientation of non-square connectors, the rotational flexibility inherent to square plates can often be overlooked by truss assemblers. This flexibility may result in misalignment, particularly if operators are unaware of the implications of plate rotation. Orientation is significant due to its effect on tooth-to-grain engagement; testing demonstrates that misaligned plates can diminish joint strength by 30%–40%, as documented by ICC-ES evaluation data.
Consequently, it is imperative for engineers and plant managers to assess whether their teams can distinguish between optimal and suboptimal plate orientations—and whether they are consistently verifying this during production.
The Benefits of Visualizing Tooth Orientation
Visual inspection of plate tooth orientation during QC offers clear advantages:
- Immediate validation that plates are rotated for optimal grip.
- Assurance against splitting or premature joint failure from misalignment.
- Effective training for new fabricators and QC staff.
- Confidence that trusses meet ANSI/TPI 1 and ICC-ES standards.
Directly seeing orientation helps prevent costly errors. For instance, Simpson’s design software displays tooth placement in Truss Studio and CS Producer reports to support proper installation. Shown are three images from Simpson Strong-Tie.
The Bottom Line
In summary, plate placement and tooth orientation are critical aspects of truss performance. As automation becomes increasingly prevalent within the industry, quality control conducted by skilled personnel continues to be essential. It is imperative that designers and builders give priority to orientation verification in order to ensure structural integrity and regulatory compliance.
Maintaining the quality of your products will produce a better outcome for you, your customer, and the end user.
An ANSI/TPI 1 3rd Party Quality Assurance Authorized Agent covering the Southeastern United States, Glenn Traylor is an independent consultant with over 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, expert witness and ANSI/TPI 1 compliance assessments. Glenn provides new plant and retrofit designs, equipment evaluations, ROI, capacity analysis, and CPM analysis.
Donna Marino is Senior Technical Writer, Simpson Strong-Tie