Often component manufacturer facilities’ owners and managers state how floor truss fabrication is generally more straight forward and simpler to train when compared to roof truss fabrication. The guidelines are easy to follow and drawings generally do not require special rotation or positioning. In all cases, the floors are fabricated on a machine designed to facilitate accurate construction and tools are available to ensure square, tight, and effective joints and plate embedment.
The most frequent issue is plate placement. Proper plate placement assumes the plate is held flush with the top chord. On occasion, some plants tolerate a ¼” off the top edge to ensure the plate doesn’t protrude above chord causing problems with installing sheathing. This is acceptable, however, ¼” should be the maximum allowable. Holding flush is a better standard and here is why. Dropping the plate ¼” reduces the tooth count on the chord member by almost 17%. Dropping another ¼” to ½” total reduces the tooth count 33%. Another ¼” results in a 50% reduction. Sometimes this is caused because the builder is concerned about the plate extending over the edge. When holding the plate along the edge with fingers extended, a positive positioning is simple to achieve. Sometimes the builder follows the edge of the chord and adjusts due to wane. This is never proper. Plate placement should maintain holding to the edge of the chord regardless of the wane to ensure all available face is used. When wane exists, additional plate LENGTH is necessary to provide adequate tooth count. In this example, a 3 x 4 plate per the design was used, however, the location was dropped to the edge of the wane. This is not acceptable. A 3 x 6 or larger plate should have initially been installed (shown in red in the photo) to accommodate the wane. A repair of the same joint, however, would need a much larger plate to account for the 50% reduction caused by plating in the previously plated area.