Frequently Asked Technical Questions

It is critical that permanent top chord bracing is supplied by proper nailing of the valley truss bottom chords to the carrying truss top chords, through purlins or properly installed rated roof sheathing. If the sheathing is not carried through under the valley framing, then the permanent top chord bracing must be supplied in another manner. There are actually a number of different conditions where a similar issue arises: where the over framing runs perpendicular to the trusses supporting it (like valley framing and some truss-on-truss framing) and where the over framing runs parallel to the trusses supporting it (like multi-piece trusses or piggyback trusses). The design of the permanent structural bracing system to transfer both vertical and lateral loads within the roof system and between the roof system and the structure is the responsibility of the building designer. John Meeks, P.E, discusses most of these conditions in detail in the Commentary for Permanent Bracing of Metal Plate Connected Wood Trusses in SBCA’s Metal Plate Connected Wood Truss Handbook. However, he does not specifically address the condition where the valley framing is carried out with valley truss frames (not actually trusses, but traditionally called so). Must the roof sheathing be carried through underneath valley trusses?

If trusses blew down from insufficient temporary bracing and the contractor put them back up without the knowledge of the truss manufacturer and gave the truss manufacturer a letter stating that the trusses were okay, is that sufficient? Do you know of any truss manufacturer who would accept this?

Are there any associations that have recommendations for the installation of wood trusses?

What are the requirements on the permanent bracing of bottom chords? Can gypsum board diaphragms be used?