A framing contractor is preparing to install a large, heavy roof structure using engineered trusses. To prevent lateral instability during erection and before the sheathing is applied, what type of temporary bracing is most critical for the top chords of the trusses?
- APermanent lateral bracing
- BDiagonal bracing from the bottom chord to the top plate
- CWeb member bracing
- DContinuous lateral restraint (CLR) bracing
Show answer & explanationAnswer & explanation
Correct answer: D. Continuous lateral restraint (CLR) bracing
Continuous lateral restraint (CLR) bracing, also known as continuous lateral bracing, is crucial for the top chords of trusses during erection. It consists of a continuous ribbon of lumber (typically 2x4s) nailed perpendicular to the top chords, typically at mid-span, to prevent them from buckling or rotating laterally before the roof sheathing is installed, which provides permanent lateral support.
Why the other options are wrong
- A. Permanent lateral bracing is installed after sheathing, not during erection for temporary stability.
- B. Diagonal bracing from the bottom chord to the top plate is more for overall plumb and stability, not specifically for top chord buckling.
- C. Web member bracing is primarily for slender web members, not the main top chords.
Temporary Truss Bracing (Top Chord)
Temporary bracing, specifically Continuous Lateral Restraint (CLR) bracing, applied to the top chords of trusses during erection to prevent lateral buckling or rotation until the roof sheathing provides permanent stability.
- Crucial for stability during erection, before sheathing is applied.
- Typically a continuous rib of lumber perpendicular to top chords.
- Prevents buckling and rotation of unbraced compression chords.
Memory trick: Erecting trusses? Keep them straight, before it's too late!