It seems like a simple thing—connect lumber together with connectors creating a top or bottom chord for your floor trusses that exceed your lumber length inventory. It’s one of the simplest applications of metal connector plates. But, while the task seems obvious, there are several important elements to it that are missed sometimes.
ANSI/TPI 1 requires the connection to be as tight as possible with no more than a 1/16” member to member gap and the plate should be positioned to provide adequate tooth count per the design drawing. Member to member gap is limited to 1/16” per section 3.7.6.1.
A Picture is Worth a Thousand Words
The first photo illustrates an example of well-placed chord connectors on a floor truss (see Figure 1). [For all photos, See PDF or View in Full Issue.]
The subsequent photographs illustrate several problems encountered when jigging or when equipment struggles to align key elements of the chord splice.
The second photo (Figure 2) shows the plate angulation issue. The connector is skewed and extends beyond the boundary of the truss profile.
The two sketches in Figure 3 deal with misalignment of chords as the chords are spliced. The potential results of these scenarios are shown in the photos that follow, with the top image here demonstrating Figure 4 and the bottom image representing Figure 5.
The photo in Figure 4 shows that an extra-wide chord width is created. In this case, the shift of the chords has created a 3-3/4” width configuration, rather than the expected 3-1/2” chord width. This often creates a plate embedment issue for the web connections.
The photo in Figure 5 shows how the plate is distorted once the webs are pressed. In this photo, the chords do not align when spliced but the chord is “straightened” as the floor truss webs are installed.
Boards spliced together with an offset creates several problems. As seen in the photograph, the connector is distorted, creating a poor tooth grip. It also creates defects in the connector and can create an extra-wide area in the floor truss as the webs are pressed, preventing proper embedment of the web connectors.
Key Points to Remember
- Connection gap is limited to 1/16” per section 3.7.6.1 in ANSI/TPI 1.
- Though not discussed here, defects in the plated area can impact tooth count.
- A good rule of thumb is the use of the longest lumber possible in your inventory.
- Avoid splices in the middle of the truss, especially over the center chase.
- Spliced chords should align with each other to avoid distortion of the connector.
- Connector should be aligned with the chord, so they do not extend beyond the profile of the floor truss.
- Level both tables on each side of your splicer to assist in proper alignment.
- Take special care to place connectors.
- When splicing on the floor truss table without a dedicated splicing machine, monitor the results of your splicing closely.
- If connectors are removed and the chord material is reworked, swap ends so new wood is used at the splice.
Another good idea, although not related to plate placement or member to member gap, is to make sure chords are marked before or as they are spliced to ensure the proper chords are used. They should be designated Top or Bottom because often they are designed differently.
The Bottom Line
Floor truss splices require some dexterity. Take a little time to review your operations. Make sure to monitor defects especially in the plated area on splices. This can be done using your plate placement analysis but generally needs to be done before final floor truss assembly.
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.