We're installing an engineered wood flooring in a room that already has a plywood subfloor. The engineered flooring will be 1/4" shy of the height of the hardwood in the other rooms, so I'd like to make up that difference underneath. My original thought was to use 1/4" XPS but that seems like it may not work.

If I go the 1/4" plywood route, what kind of connection do I need between the two subfloors? Can I just float the 1/4" on top? Or do I need to affix them together? If the latter, would some 1/2" brads be enough? Do I need to glue and screw?

  • 3
    I'd screw, not glue. Definitely not brads. Just enough screws to keep them in place, mind you, no need to go overboard – GdD Oct 24 '12 at 20:51

Have you considered using cork as an underlayment? I believe they make them in various thicknesses, including 1/4". It's very easy to work with (you can cut it using a utility knife) and it helps dampen sound.

  • that's an interesting option! I'll need to look into that. – DA01 Oct 27 '12 at 18:26
  • I ended up using cork. It worked perfectly! – DA01 Aug 19 '20 at 19:08

You could simply install a transition piece between the two rooms.

But if you're determined to get them to match up, then 1/4" luann board will do nicely. Glue and screw - 1/4 bead of glue distributed evenly over each board, screws on a 1 foot grid.

NOT going overboard is what leads to squeaky, shifting sub-floors that make for a shoddy looking finished product.

  • screwing down some luann is fine, a layer of red rosin paper between layers will also avoid squeaks. I would put down some adhesive personally, takes out any bounce as well as squeaks. – shirlock homes Oct 24 '12 at 23:49
  • What about using a cork underlayment instead of luann? Since it's engineered, cork won't interfere with the attachment of the wood flooring. Plus it'd give a nice sound dampening effect. – Malfist Oct 25 '12 at 14:19
  • I don't understand why it's being engineered vs. not engineered has any impact on the attachment of final flooring? – The Evil Greebo Oct 25 '12 at 14:49
  • I think he means it's a floating floor (because it's an engineered floor) so don't have to worry about glue/nails. – DA01 Oct 27 '12 at 18:27
  • Exactly, engineered wood floors are often floating floors and don't need to be nailed down. – Malfist Oct 29 '12 at 12:18

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