Are We Designing Our Components to Benefit Our Truss Builders and End Users?

Many years ago, early in my career as a truss designer, I was interrupted by the production manager. He loudly entered my office with a piece of 2 x 12 and a circular saw and abruptly slammed both on top of my drafting table that was sporting a newly created truss layout. (We did not have integrated layout programs at that time.) He exclaimed to me, “you designed it, you build it!” then stomped out of the office. Being obstinate, I followed him up the hill to the truss plant and proceeded to cut the 2 x 12 into a very long scarf cut. To my chagrin, the saw blade repeatedly binded in the sappy southern yellow pine, causing the saw to stop as the saw kerf closed as I cut, relieving the internal strain of the lumber. I was better suited to sitting in an office setting. I struggled to cut one piece, but I did not show my struggle. I exclaimed to the plant manager after I finished, “There you go! That’s how it’s done.” Although I proved to the manager that I could do his job and my job, I knew I was busted but did not want to admit my mistake. I walked briskly back to the office as the manager yelled “you have 38 more of these to cut!”

This experience caused me to reconsider my truss designs. With very little truss building experience, I was unable to comprehend the impact of my designs. I was not aware of how I could influence production, nor was I aware of how I could improve my output to the benefit of the truss plant. Admittedly, this process of learning compassionate design required years of design experience and empathic understanding of the production process. It wasn’t until I actually built a truss that I realized how important my efforts with a stroke of a pencil or pen could seriously hamper productivity. Not only that, but I was also creating problems and issues for our end user by not considering how my designs could be mis-installed or mis-built.

Let’s look at a few items that have a great impact on production and relate to the product installation. These items are suggestions and can vary depending on the equipment a facility has at its disposal. Sometimes skills are important to keep in mind too.

1. Design to create a builder-friendly, end-user-positive experience. Optimize webs and chords to keep parts count simple.
2. If the bundle of trusses is very similar, try to keep them as similar as possible.
3. Consider building common truss and gables with the same chord materials.
4. Consider limiting lumber grade selections, and use higher grade lumber for girders rather than multiple selections within the same truss or project.
5. Avoid complicated plate size changes, especially each heal assuming they are similar.
6. Limit the SKU (Stock Keeping Unit) inventory of connectors to a reasonable number. This depends on the plant and product mix, but the less the better for sorting, picking, and inventory of connectors. While larger inventories reduce plate consumption, it also increases errors.
7. Use vertical webs because they help builders control profiles. This is true for floors and roofs.
8. Single-cut webs can create variations in lengths when cutting on a component saw due to bows in the lumber, so recommend double-cut when possible.
9. On bottom chords, always build with a butt cut. We also recommend increasing the butt cut to ½” to help plating and fit when using older saws with less calibration control.
10. Eliminate long scarf cuts if possible with 4-sided wedges or sliders. Even if your linear saw will cut a 60” scarf, the variations and undulations in lumber will make these cuts difficult.
11. Consider making interior bearing trusses symmetrical in design to allow for flipping trusses end for end. This includes upsizing connectors to make a switchable, flippable design.
12. Long panels make less pieces, but long panels make it very difficult to control bows in lumber, so consider limiting panel length as practical.
13. Consider splicing off panels. This will help in controlling the crown in lumber, even if it increases the number of joints on a truss.
14. Avoid sloping flat trusses that create webs with very small increments of change. If you still must build them, make sure the web material is marked clearly and adequately. Unfortunately, linear saws make these webs very difficult to sort.
15. Avoid long job names or numbers. Truncated job numbers are easy to remember and write. As an alternative, invest in a truss tag printer and a decent ink jet printer to print onto parts.
16. This one is controversial but here goes. One-foot, three-foot, and five-foot corner jack methods make jacks easier to build, but consider alternatives instead. At the jobsite, these designs require splices in roof sheathing and waste a significant amount of materials. The field cuts create edges that absorb moisture more rapidly, creating a bulge in roof covering that telegraphs through roofing years later.
17. Consider starting step-down hips from the peak of the roof spaced uniformly.
18. Consider nailing an additional truss to a gable end, because it’s sometimes easier and more effective than building a structural gable end with its many small parts and pieces. Sometimes it’s even cheaper given the special labor required with structural gables.
19. Use valley sets rather than running profile to avoid extra members. This keeps like trusses with like and it makes it easier for the framer to align the trusses. Complex profiles create many issues including complex bracing requirements.
20. Space valley sets from a common truss to avoid odd spacing of sheathing. This will help eliminate field cuts and the additional complications associated with them.
21. When designing studio vaults, allow for the framer to continue the wall or to adjust the vertical to match the wall below. This will require the designer to keep the detail as a cosmetic component rather than a structural element.
22. Consider numbering floor trusses to designate floor level, which will make the erection much more exact.

Of course, there are many more considerations that could be listed, but this is a good start. This general list of things to be aware of when designing trusses should help a truss designer consider what happens after their design moves from their desk to the next step in the process. And, one more thing to consider – a little experience in the truss plant building trusses isn’t a bad idea either. Some of the best designers I know spent some time in the shop or, better yet, started in the shop!

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.