Wedges—Misunderstood and Underappreciated?

The lowly wedge sometimes gets very little respect. If your plant is doing it right, the wedges usually are cut from drops or culls. That’s a good way of doing it, and it sounds very simple, but not just any piece of wood is suitable for a wedge. There are important qualifications that must be taken into consideration, and some truss manufacturers may not be aware of the potential pitfalls. To make matters worse, today’s linear saws don’t look at the material being cut. The machine assumes all the lumber is fully faced and usable. Often, no one looks at the parts cut until they are at the table to be used in the component.

The problem with the wedge may include the following:

1. Wedges are often cut from scraps, but sometimes the sawyer deems that it’s ok to cut it from scrap (minus the first “s”). Wedge material needs to be solid and free from serious defects. Don’t cut it out of trash.
2. Many designs require the wedge to transfer some of the highest loads found in the truss. These designs don’t allow for any defects. Of these designs, analyzing the TPI requirements using the plate placement method, the generated template will show defect circles for the top and bottom chords but no circle to graphically illustrate allowable defects for the wedge component. This is because no defects under the plated area are allowed for the particular design.
3. Pressing a connector plate is traumatic for a small component like a wedge. Sometimes the wedge needs to be more solid and defect free just to make it through the roller press.
4. A typical amount of wane on a wedge as a percentage of the piece is very significant compared to typical wane on a web or chord member.
5. Rarely does the sawyer really know what truss design requirements are specific to the piece they are cutting. As a matter of principle, neither does the builder. Wedges, in order to be consistently used, correctly require a higher degree of quality across the board.
6. It’s easier to cut good wedges than to gamble with questionable materials.

For these reasons, best practices should require top materials, with all sides square and free from loose knots and wane. This will help assure a quality truss every time.