Cross bracing floor joists

[Mark Bolton]

The strapping does everything to prevent roll, nothing will completely eliminate it, and the instant you reduce your roll you immediately start to fire more adjacent joists when a load is applied (the more you can fire the stiffer). The strapping from sill to sill creates the "triangle" from joist to joist and then a larger triangle at the cross section of the entire floor from sill to sill, and in one step, with minimal fasteners.

Very few joists fail completely in vertical deflection, they roll first, mostly because unless you completely eliminate the roll (torsion box) its technically going to be there on some level.

Try it for your self. Stand a 2x on edge and apply a substantial load in the center, it will flop over on its side before it will snap on its width. Same deal.

Im telling you, put your money where your mouth is and try it.

[Ole Anderson]

The strapping does everything to prevent roll, nothing will completely eliminate it, and the instant you reduce your roll you immediately start to fire more adjacent joists when a load is applied (the more you can fire the stiffer). The strapping from sill to sill creates the "triangle" from joist to joist and then a larger triangle at the cross section of the entire floor from sill to sill, and in one step, with minimal fasteners.

Very few joists fail completely in vertical deflection, they roll first, mostly because unless you completely eliminate the roll (torsion box) its technically going to be there on some level.

Try it for your self. Stand a 2x on edge and apply a substantial load in the center, it will flop over on its side before it will snap on its width. Same deal.

Im telling you, put your money where your mouth is and try it.

Not sure what you mean by "fire" Not a term I heard in my structural engineering classes way back in the middle ages. I need to see a sketch to visualize the triangle of which you speak. The proper term for roll would be buckle where the ends of the joist remain vertical and the joist twists. And if just strapped, if one joist buckles they all buckle. Proper bracing will totally prevent buckling such that failure from overloading will be by wood failure rather than buckling. I get your torsion box analogy, the top of the box being the continuous floor, but strapping is far from the horizontal support offered by a continuous ceiling of structural sheet goods, that being the bottom of the box.