Truss Deflection Onto Non Load Bearing Walls
I am installing a 40-foot scissor truss that is designed to deflect about ½ inch. I am concerned that the deflection will cause an interior partition wall to pick up some load from the truss and transfer it to the floor system. Should I double up the I-joists under this partition to pick up the extra load?
To get an idea of how much load will be transferred, ask the truss manufacturer to analyze the truss with an additional bearing point at that location.
Keep in mind that there are a lot of variables that affect how much load the truss will transmit at the unintended bearing wall. If the intersection with the truss is not near a truss panel point, chances are that it should not be a huge concern. The actual load transferred might be even less than the load calculated by the truss manufacturer, because the floor is a lot less stiff than the solid bearing that the truss design assumes. It goes back to that old engineering adage ”stiffness attracts load,” so the less stiff the bearing location (in this case, truss mid-panel) and the supporting floor below the partition wall, the less load it will pick up. If you are very concerned, then yes, you might want to double up the joists at that location. The question then becomes, based on the analysis of the additional bearing location, is that enough?