I am currently replacing carpet with hardwood flooring. The subfloor is OSB laid on-top of joists. The hardwood manufacture has recommended that a layer of 1/2 plywood be added to the subfloor in order for the hardwood fasteners to properly hold.

I have a few questions about the proper way to do this (assuming my strategy is valid):

  1. The hardwood manufacture recommended gluing the new plywood layer to the OSB and securing it with additional fasteners (I was thinking screws that go through the OSB and into the joists by an inch or so). Is there any issues with this strategy?
  2. If the plywood is glued to the OSB, should I ensure that the seams of the two layers line up (or on the opposite end make an effort to stagger them)?
  3. Would it be okay to leave a small gap (around ~ 1/8") around the perimeter of the room between the new layer and the drywall? This would make it so I don't need to undercut the drywall to fit the new layer underneath.
  • Will the room have baseboards (skirting boards ala commonwealth, I think?)
    – Ecnerwal
    Commented Aug 2, 2023 at 13:07
  • @Ecnerwal yes the room will have baseboards around 3/4" thick Commented Aug 2, 2023 at 13:14
  • When laying a second layer for tile, you don't want to attach the second layer of subfloor to the first with glue, and you don't want to screw into the joists so you would only use a 3/4-1" screw. The reasoning being that the layers will allow for more independent movement providing some decoupling. I would think this would be prudent in this case too
    – redlude97
    Commented Aug 2, 2023 at 22:57
  • The OP is installing a hardwood floor.
    – RMDman
    Commented Aug 2, 2023 at 23:47
  • Honestly, I don't think it matters whether you screw the new layer to the joists or not if you're gluing. The screws are there just to pull the two layers together until the glue cures.
    – Huesmann
    Commented Aug 3, 2023 at 13:48

1 Answer 1


Stagger the seams from what is currently down.

Your screwing and gluing plan will work nicely.

A 1/8 gap to the wall is fine.

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