Minimum top and bottom chord permanent lateral restraint/bracing of structural roof or floor trusses is assumed to be adequate when using code-compliant roof and/or ceiling diaphragms. This lateral restraint/bracing is typically accomplished with code-compliant roof /floor sheathing and fastener spacing and/or code-compliant gypsum ceiling material and fastener spacing or purlins at a given on-center spacing. This information is customarily indicated on each truss design drawing.

However, when assemblies are specified for fire or sound rating, the assembly may call out either resilient channel, furring channel or hat channel at a given on-center spacing. If a single layer of gypsum is specified in the assembly, frequently the metal channel would be directly attached to the bottom chord of the truss and the gypsum is then attached to the metal channel. Where two or more layers are required, the base layer is typically attached to the bottom chord of the truss, so the bracing requirement is met.

The question addressed by this research report is how the lateral restraint/bracing requirements may be met when the gypsum sheathing is not directly attached to the bottom chord.