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I am intending to instal self stick tiles over a primed luan underlayment in a bathroom. However, the manufacturer's instructions clearly state:

DO NOT install over unsuitable or unstable subflooring such as chipboard, OSB, luan plywood, mahogany based plywood underlayments, Masonite™, cement board, fiber based backing boards, or any other non-underlayment grade panel

In trying to understand why the luan would cause an issue, whereas plywood would not, I've since read that luan contains certain "extractives which adversely affect the "cure" of mastic adhesives."

I'd like to find a way to make this work without needing to tear up the newly installed underlayment. Will the primer help in this regard? Is there any additional prep I can do to maximize the probability of a successful installation / adhesion?

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    You might contact the manufacturer of the self stick tiles and see if they have any recommendations but I'd either look for a different tile product or remove the luan and replace it with an approved product.
    – jwh20
    Commented Nov 9, 2020 at 15:02
  • @jwh20 - yes, I've left them a message. I figured this was a common enough scenario that someone here might have some suggestions.
    – Eaten by a Grue
    Commented Nov 9, 2020 at 15:03
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    There is a 1/4 inch plywood underlayment And there is luan Luan is cheaper and will dent very easily I use luan for non flooring applications but only use the plywood underlay with the x’s that indicate the nailing pattern under vinyl flooring Years ago there was a bad reaction between vinyl adhesive and luan resins on numerous vinyl floor jobs that caused discoloration of the vinyl.
    – Kris
    Commented Nov 9, 2020 at 22:13
  • Just take the luan off. It's just trash that's in the way. Luan is an underlayment, but not the underlayment for everything. It worked well perhaps for the ceramic tiles that were there before, but it's obsolete for that purpose, and most other imaginable purposes. There's basically no need for it. It seems like something made to cause trouble and be sold cheaply and has no imaginable benefit today, in any permanent household application. Crafts and scenic props for a short production are about its only reasonable uses. Stick on tiles don't need underlayment when subfloor exists.
    – Kuba hasn't forgotten Monica
    Commented Mar 8, 2021 at 19:11
  • One possibility is that the manufacturer has had prior experience with (or information about) tile products installed on luan plywood, and it didn't go well.
    – Technophile
    Commented Jan 15, 2023 at 18:24

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  1. Luan plywood tends to have a ton of resin and other chemicals in it (due mostly to the species of wood used). This can leach out and stain tile grout or vinyl flooring (or cause adhesive issues due to salts, etc.).

  2. It's a very soft plywood, so it may not have enough rigidity to support the floor and prevent dents.

  3. It tends to have voids in the interior plies. See previous point.

  4. It isn't made with an exterior grade adhesive. This means any water can cause quick delamination and swelling.

  5. In general, it's cheap crap and not up to the task. Use it for theater props instead.

If you were to seal it against stains, and if you were comfortable voiding your flooring warranty for puncture damage, you can probably get away with it. If you've already primed I'm not sure how you'd accomplish that.

To preempt any grumbling about Big Orange, et al, selling Luan plywood, when I worked there (many years ago, granted) they made every effort to inform customers about its unsuitability for flooring. People demand cheap, and so they sell the stuff, but it's not their fault if it's misused.

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  • thanks - to be clear, the luan is only a final layer which sits atop 5/8" play and the subfloor so there is plenty of rigidity here. I'm not concerned about stains.. I'm not sure how a stain would make it's way through primer, paint and vinyl grout anyway - does that seem likely to you? I wish I'd known what I know now before installing it. Thanks for the input.
    – Eaten by a Grue
    Commented Nov 9, 2020 at 18:54
  • Yep, that's what underlayment is. No, there isn't plenty of rigidity. We're just talking about the surface, and if the (usually single, thick) inner ply has gaps in it you'll have dents in your floor. Yes, stains do migrate to the surface. See many posts here about stains coming through wall paint.
    – isherwood
    Commented Nov 9, 2020 at 20:08

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