I’ve been asked: do you always need a shop drawing or the engineering to inspect a truss? The quick answer if you are conducting an ANSI/TPI 1 Chapter 3 audit is that you must have a design drawing that specifies plate sizes, placement, and lumber grade requirements in addition to overall heights and overall lengths of the truss. This information must be verified and recorded as inspected. Any deviations must be noted with the inspection paperwork. This can be done with paper or digital methods as long as the information is genuine non-preferential.
But, not all “inspections” have to be official, and your frequent visits to the assembly area can be productive even when you’re not carrying around design information.
Often, plants have projections of the design at the table or lasers are projecting critical information.
An effective system prints plate location and information directly on the lumber, making quick observations easy.
In fact, there is a category of inspections that can be made by anyone, which I call the “low hanging fruit.” Here are some examples. For all photos, See PDF or View in Full Issue.
The first photo shows excessively rotated connectors, which is a frequent non-compliance issue. Standards require no more than a 10-degree variation. Keep in mind that some designs have a 5-degree variation and rarely a zero-degree variation.
Large member-to-member gaps are easy to see, such as in the second photo. Your familiarity with 3-1/2” faces makes it fairly easy to see when a gap exceeds 1/8”. If it’s close, you might need a tape measure or better yet a 1/8” gauge.
The third photo is another example of excessive rotation. This should be easy to see unless it’s on the bottom side. Often this happens on the back side of the truss, so it may not be as apparent.
Wildly misplaced floor truss splices are also easy to see. The one in the fourth photo seems to be pretty obvious. This one effectively replaces your 3x10 with a 3x6 capacity connector. That is a 40% reduction in the designed connector, assuming the back plate is similar.
The problem in the final photo might not be as easy to recognize at first glance but, with experience, this situation should shine like a blinking light. Chord splices normally require a significant amount of plate covering the splice. Not always but most of the time, and this plate is placed too high. This is a common mistake by inexperienced builders. Also note the cut on a web, which is not against the vertical.
The Bottom Line
In addition to formal inspections when you need to have your documentation, many mistakes can be identified with simple observations. These photos have shown the most common examples, and you should consider posting them in the shop, so everyone can use them as prompts to ask questions.
Remember, the more you can educate the people working in your plant, the more they will be able to maintain the quality of your components. Anyone who sees a mistake ought to be able to recognize it, which is the first step in getting it fixed before it leaves the shop.