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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9 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.

  3. Shaun Says:
    February 11th, 2015 at 12:33 pm

    I will be installing tile on my brothers new home. This is the first time i will be using the underlayment rather than the backerboard and was wondering if I should be putting down like an 1/8 sheet of plywood just in case they plan on removing this floor in the future instead of bonding it right to the permanent subfloor? What is your suggestions?

  4. Mike Says:
    February 24th, 2015 at 1:15 pm

    I just removed the hideous pink tile floor from my master bath. It was layed directly onto the plywood subfloor – 25 years ago. *Zero* cracked tiles, *zero* cracks in the grout. It was in perfect condition and that bathroom was used daily for 25 years.

    So why are people recommending backer board or some other membrane?

  5. scott Says:
    March 31st, 2015 at 11:06 am

    I too, just removed original tile from a mid 70’s house that was directly on plywood subfloor….no crack and grout was perfect, however, they did not use thinset to adhere the tile, looked like a standard construction adhesive. Any thoughts?

  6. Russell Rivera Says:
    April 20th, 2015 at 8:49 am

    I have laid tile directly over plywood and it will work in small areas but when you have big areas of tile I would use some kind of backer board

  7. Joshua Says:
    April 24th, 2015 at 1:03 am

    I am tiling bathroom floor that is roughly 60inches by 60 inches. Is backer board really necessary?

  8. lenny Says:
    May 20th, 2015 at 8:19 pm

    I’m not a pro but I’ve done about six different bathroom and kitchen floors as a fussy DIY-er. I’ve had good results with tile set in thin set on plywood as long as I get two things taken care of.

    One – the subfloor needs to be stiff and solid. When in doubt add blocking in the joists (if you can get at them) and more screws in the subfloor to make sure.

    Two – paint the plywood with some waterproofing / crack isolation membrane. It’s not necessary to make it fully waterproof just resistant enough so that moisture that gets through the grout joints mostly dries out back through the grout instead of through the wood.

    My oldest floor is 15 yrs old and still looks great. Unless the floor gets really wet on a daily basis this should last indefinitely.

  9. Richard Says:
    May 27th, 2015 at 7:44 am

    We have our large kitchen and hallway that was originally covered by 12 X 12 ceramic tiles on top of 3/8th inch plywood. Thin set was used instead of glue or adhesive. the floor tiles became loose, cracked and ugly looking over about 2 decades of use. Now the entire flooring of ceramic tiles needs to be torn out and replaced. we are thinking about having the 3/8th inch plywood torn out and replaced by 1/4 inch concrete board before the new tiles are installed.
    any thoughts??

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