Originally Posted by Ron6519
I'm not sure it's blocking. The cross bracing in the ceiling is metal, not wood. It looks as if there's another flooring system coming in from the side. The spacing is wider then the other floor structure, so I'd check it out first
What's on the other side of the wall?
Jeff...I'm with Ron on this one.
It isn't just regular blocking. It appears that the wall that these blocks go over is an exterior wall. If the outside joist, your box joist, actually hangs out past the lower wall framing, then that blocking is in place to keep the joist there. If not, then it is likely nothing more than backing for a future ceiling.
A better and simpler solution for backing (if that is in fact it's purpose) would have been a 2 x 4 nailed on top of the top plate and protruding an inch or so to act as the backer.
It is quite common for upper floors to extend out past a lower floor, but usually the distance is more than what appears to be there.
My best guess is that it is nothing more than backing.
As for the metal bridging, I see only one "X" and then a single piece in the next space. You might benefit from adding some decent blocking down the centerline of the joists, or even two rows if the span exceeds 14'.