Why is it a bad idea to install self-stick tiles over luan plywood?

Question

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?

Answer 1

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.