If the code requires a 2x8 at 16 inches on-center, then use a 2x10 of the same grade and species. This may not be the most cost-effective solution in every case, but it's easy to remember and will save time and worry. But even at 12 inches on-center, the joists are not close enough for the shock of a foot to be carried by two joists. Glue and screw the sheathing. Floor sheathing should always be glued down.
Screws work better than nails for long-term bounce control.
To use this chart, locate your required clear span in the Lmax columns. In adopting this rule, we encourage builders and designers to ignore the reduced live load of 30 psf for sleeping areas, and instead use the standard 40 psf live load for all rooms. After all, a bedroom can become a study or home office, and the traffic may be heavier than in a living room. The consensus among wood truss professionals is that strongbacks are effective in minimizing annoying vibrations, and that they are well worth the time and money it takes to install them. Table 2 illustrates the expected performance of various floor truss designs, using a 40-psf live load.