A remodeling contractor wants to attach a new mechanical unit that will impose a 200-pound point load on the bottom chord of a manufactured wood floor truss, at a location not shown as a load point on the truss design drawing. What is the correct course of action before installation?
- AAdd a single sistered 2x4 alongside the bottom chord at the load point to reinforce it
- BObtain analysis and written approval from the truss designer or a qualified engineer before adding the load
- CRelocate the load to the nearest panel point without further review, since panel points are always adequate
- DInstall the load since 200 pounds is minor and unlikely to affect a manufactured truss
Show answer & explanationAnswer & explanation
Correct answer: B. Obtain analysis and written approval from the truss designer or a qualified engineer before adding the load
Manufactured trusses are engineered for specific loads at specific locations shown on the truss design drawing; adding or relocating loads without engineering review can overstress chords or connector plates and cause failure. Code and manufacturer requirements mandate that any deviation from the original design be reviewed and approved by the truss designer or a qualified engineer.
Why the other options are wrong
- A. Field reinforcement without engineering analysis does not guarantee adequacy and is not code-compliant.
- C. Panel points are only adequate for their originally designed loads; relocation still requires engineering review.
- D. Even small point loads at unintended locations can overstress truss members or joints; assumption of safety is not permitted.
Truss Modification Rule
Manufactured wood trusses may not be cut, notched, drilled, or loaded outside the parameters of their engineered design without prior review and approval from the truss designer or a qualified engineer.
- Truss design drawings specify approved load points and magnitudes
- Field modifications without engineering approval violate code and manufacturer requirements
- Point loads at non-designed locations can overstress chords and metal connector plates
Memory trick: 'New load, new drawing—call the truss engineer before sawing.'