When a load is applied to a truss it will deflect. The degree to which the truss deflects is a function of the trusses’ geometry, material properties, span, and applied load. The building code provides deflection limits for individual trusses.

Structural floor or roof trusses are typically placed in a spaced pattern as part of the supporting structure. When the loading, span, or geometric properties of these trusses vary, the resulting deflection will vary as well. The difference between the deflection of adjacent trusses is called differential deflection. When the differential deflection is high it can cause cracking in finish materials or even result in structural performance issues. This guide will discuss differential deflection and provide recommendations to limit its impact on the structure.