So we went and worked on one squeaky floor today. We found a few issues and the big oops was nails that missed the floor joist.
The ones actually touching the side of the floor joists can make alot of noise, we were able to pull them thru the floor with end nipper pliers. When you install the sub floor with glue, you never put glue where it will get into the tongue and groove but I think this guy went for coffee and left glue on one joist. So when he nailed the floor down on dry glue, the glue didn,t squish flat and it held it up 1/8" except for the area near the tongue and grove which would move when walked on.
The fix; We took 12 inch peices of 2x6 and went a little crazy with floor glue on one side and one edge and pushed it up tight to floor and nailed it to the joist. It seemed to work.
The other problem we had was the span of the floor, it had 16 ft 2x10s 12" on center. Engineers tell me that it works but each floor joist deflecks 1" when someone walks accross the floor.