Residential Building Inspector B1Roof-Ceiling ConstructionHard
During a roof inspection, an inspector notes that the roof framing consists of trusses with a bottom chord used as the ceiling joist. The trusses are spaced 24 inches on center. What is the minimum required size for collar ties or rafter ties in this type of roof construction to resist rafter spread, assuming a typical roof pitch and span?
- ACollar ties are not typically required with trusses.
- BRafter ties are not typically required with trusses.
- C2x6s spaced at 24 inches on center.
- D2x4s spaced at 48 inches on center.
Show answer & explanationAnswer & explanation
Correct answer: B. Rafter ties are not typically required with trusses.
Roof trusses are engineered components where the bottom chord inherently acts as a tension tie to resist rafter spread. Therefore, separate rafter ties or collar ties, as defined for conventional stick-framed roofs, are not typically required when using trusses.
Why the other options are wrong
- A. Collar ties are for conventional rafter systems, not trusses.
- C. This describes a tie for a conventional rafter system, not applicable to trusses.
- D. This describes a tie for a conventional rafter system, not applicable to trusses.
Truss vs. Rafter Ties
Roof trusses are engineered to contain horizontal thrust within their design, eliminating the need for separate rafter or collar ties typically required in conventional stick-framed roofs.
- Truss bottom chord acts as a tension tie.
- Collar ties and rafter ties are for conventional framing.
- Trusses are designed as a complete structural unit.
Memory trick: Trusses are complete, no extra ties to meet.