Structurally, an open-web floor truss resembles an I-beam in that it puts most of its material along its top and bottom edges where stresses are greatest. To strengthen a truss, the fabricator may double its top and bottom chords, make side-by-side girder trusses, use larger truss plates or stronger wood, or use some combination of these techniques.
Login or Register to download the PDF version of this guide. (337.45 kB)
Figure B: Lifting Floor Trusses by Crane
When receiving a truckload of trusses, reject those with excessive splits in chords or braces, those with knots close to metal plates, or those with loose or deformed plates. Also reject any that show evidence of having been damaged and repaired. Beware of warped or wet lumber, which can set up dangerous stresses as it shrinks and dries.
Lifting With a Crane
If you use a crane, always lift from two points (Figure B) and never lift the truss sideways; the excess flexing can loosen the connector plates, causing eventual failure.