Hi Folks,

I have 5/8" OSB over 2x10 on 16" centers.

How should I prep the floor to run 3/4 perpindicular to the joist?

How should I prep the floor to run 3/4 parallel to the joist?

I'm assuming adding wood (OSB or Plywood) will be involved, Which I would intend to screw to the orig. subfloor.

Should I also Glue it? Pl400?? Do I need to screw it to the joists, or is the existing subfloor sufficient? What should the screw spacing be?

Thanks in advance!

Install 3/8" minimum, preferably 1/2", CDX grade plywood. You can glue and screw but if that underlayment ever needs to be repaired or replaced, you're "screwed". I prefer stapling with 1&1/4" with 1/2" crowned construction grade staples (#16 gauge). With the 1/2" CDX, you could run parallel to the joists. With 3/8" only, you will need to run the flooring perpindicular.

What Gary said, and it is a good idea to go to sand the seams and re-nail the original subfloor first. On the top layer (underlayment) leave a gap about 1/8" around each sheet, don't worry about hitting the joist. It takes alot of fasteners to do this. I don't use subfloor adhesive but I do like to squiggle out yellow wood glue when going over OSB, but as he said it's not coming up later if you do that.

Thanks for the info.

I planned on a bit of subfloor prep prior to the underlayment.

I take a ballpeen hammer and recess any nails, belt sand
any high seams, and screw out any existing squeeks.

Should I screw the osb to the joists even if there are no existing
squeeks, to ensure no future squeeks? I'm assuming the osb is nailed.

What length screw should I use for the joists, and what length for the underlayment? I'm planning on 2 1/2 and 1 5/8.

Thanks

My subfloor prep included screwing the 3/4" CDX down with decking screws, and then going back and sinking all of the nails, My subfloor was put down with framing nails, not ring-shanks, and they were backing out. Some not a visible amount, but some as much as 1/8". With the screwing and the re-sinking, the floors are close to silent. Prior to this, they were the squeekiest floors I had ever heard.