I recently bought a new spec home and the builder installed a very cheap carpet there. I decided to install a floating 5/8" thick engineered hardwood instead, and after it was installed, I realized that in a few narrow places, it was moving up/down due to the subfloor not being properly leveled (the builder did a very poor job in a lot of places).

I thought of two solutions for this:

  1. Shoot a nail with a nail gun in a few places on the floor.
  2. Drill a small hole in a few places, and drive a thin screw into the subfloor.

Obviously, I'd use wood putty so in both options nothing would be seen. I was considering option 2 because a nail is permanent, if something was to go wrong.

I am scared to do either option for two reasons. (1) what if the wood cracks? (2) does the hardwood need to expand?

I would appreciate any feedback to my concerns or any other ideas on how I can stop the floor from moving up and down.


  • did you glue the tongue and groove fittings on the eng hardwood on installation? Commented Jan 6, 2023 at 18:58
  • Is the subfloor moving, or is it just not level?
    – SteveSh
    Commented Jan 6, 2023 at 19:14
  • Be patient. Almost any flooring settles into shape over months or years.
    – isherwood
    Commented Jan 6, 2023 at 20:55
  • I didn't glue anything @FreshCodemonger
    – Manny
    Commented Jan 6, 2023 at 21:32
  • It's moving up and down a bit @SteveSh
    – Manny
    Commented Jan 6, 2023 at 21:32

1 Answer 1


They call it a floating floor for a reason. It needs to expand and contract so nails and screws into the subfloor are a bad idea. There are adhesives/epoxies that can be injected through a hole in the floor but those also prevent the floor from expanding and contracting.

If this is a new floor, you might want to wait a year to see if the floor settles on its own with the climate changes. If not, and if the floor boards "snapped" together, you might want to disassemble the floor, fill the voids and reassemble.

I know of one case where the floor was fixed by drilling holes in the new floor and gluing dowel rods in to support the new floor against the subfloor and then sanding/finishing the end of the rods to match the new floor but this was an extreme case. You might have to get use to the 'up down' areas.

  • Gotta agree with JACK. The right way, harder, but the right way would be to remove the floor and use a leveling compound. I had to do this in a rental I was refurbishing, it worked pretty well. It's a little tricky bc you have to trowel it out and use a perfectly straight board to make sure it's even/level. I know, I know, taking up the recently installed flooring is not a pleasant prospect, but it's the best way to go. Maybe, in this case, you don't want the perfect to become the enemy of the good! JACK's idea of giving it the tincture of time and see if it settles would also work. Commented Jan 6, 2023 at 20:17
  • 1
    @George Anderson - OP stated, in answer to my question, that the subfloor is moving. That means 1) the subfloor isn't fastened properly to the joist or 2) the joist is moving. In either case, I don't think a leveling compound is going to do much.
    – SteveSh
    Commented Jan 6, 2023 at 21:38
  • Thank you all for your opinion. Is there a reason you initially recommended the adhesive/epoxy over the nail/screw, since both will prevent expanding/contracting?
    – Manny
    Commented Jan 6, 2023 at 21:39
  • @MonyaFeldman I didn't recommend the adhesive/epoxy. I just mentioned it so you wouldn't try it.
    – JACK
    Commented Jan 6, 2023 at 21:42
  • @JACK oh, that makes sense, got it. Thank you.
    – Manny
    Commented Jan 6, 2023 at 21:46

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