Home Improvement Expert Danny Lipford

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Can You Lay Tile Directly Over a Plywood Subfloor?

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I’m tiling an upstairs bathroom. The floor is plywood, and I’m hesitant about using Hardie backer board because the height of the floor will be too high. Can you tile directly to plywood with thinset? -Chris

Hi Chris,

While you can lay tile directly over a concrete slab using thin-set adhesive, don’t make the mistake of applying tile directly to a plywood subfloor. No matter how firm the subfloor; the plywood will expand and contract at a different rate as the tile, causing cracks to develop in the grout lines or tiles over time.

On a plywood subfloor, you need either a layer of cement backer board or an underlayment membrane, like Schluter-Ditra, between the subfloor and tile for the thin-set adhesive to achieve a good bond.

While I prefer using 1/2” cement backer board over a plywood subfloor, you may be able to get by with 1/4” backer board instead. Even if you use a waterproof underlayment membrane, such as Ditra, the floor will still be either 1/4″ or 1/2” higher than the subfloor, plus the thickness of the tile and adhesive.

When applying cement backer board over a plywood subfloor, be sure to adhere the two surfaces together with thin-set adhesive; and screw the cement backer board down with special screws that countersink into the backer board, such as Backer-On screws available at The Home Depot.

Good luck with your project,

Danny

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2 Comments on “Can You Lay Tile Directly Over a Plywood Subfloor?”

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  1. Peter Says:
    December 7th, 2011 at 8:47 pm

    Hey,
    I’ve discovered an area of rot in my plywood subfloor between my bath tub and toilet. To my surprise, the marble tiles were laid directly on top of this plywood without cementboard (probably because the toilet drain calls for a rear flush model, and cementboard would have disrupted where the toilet and drain met).
    If I had the time to be meticulous, I’d open pandora’s box and do the whole thing right- But I dont.
    My question is whether or not I can replace the rotted subfloor with a thinner plywood and then cementboard to meet the current subfloor height, or am I in over my head with this fix?
    -Peter

  2. chonia Says:
    May 10th, 2012 at 6:27 pm

    I had carpet down on a concrete slab floor and I was wanting to put tile down but I was wanting to find a cheap and easy way to put the tile down quickly.

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