Tiling bathroom, need help with subfloor

11 years ago

This will be my first time tiling. I just removed the old tile from the bathroom, it's probably been there for 50 years. Most of it was no longer adhering to the subfloor which was plywood. When we stepped on the tile in bare feet the tiles would stick and pop off the floor...lol. So it's time.

Joists are 16" on center. I'm new to this stuff so bear with me.

When I look at the floor there are the joists, then on top of the joists are 1" thick planks about 7" wide, then on top of that there is about 1/4" plywood and then the tile.

My original plan was to remove tile, then lay Ditra on top of the existing plywood, but the plywood looks nasty. it smells and there is still adhesive on it. I guess I could sand it down.

What are my other options? I could rip up the plywood and just lay another clean new sheet of plywood and use the Ditra on top of that?

I could rip up the plywood and lay 1/4" sheets of cement backerboard?

I guess I could also lay backerboard on top of the existing plywood?

I've included a pic, it's a view down onto the floor, you see the plywood and then the 'planks' I mentioned. I just want to be sure I have a good sturdy subfloor for my tile.

Thanks for any help

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Comments (6)

mash74
Original Author
11 years ago
Couple of corrections. The plywood is actually 5/8" thick.
And when I said it smelled it's not a moldy smell or anything and there are no signs of water damage. More like a pee smell because my two boys miss the toilet and as I said the tiles really aren't sticking to the plywood anymore.
If I could remove the adhesive can I just use the Ditra over the existing plywood?
Or do I need to bite the bullet and rip the plywood up?

Thanks again
StoneTech
11 years ago
If you are using tile and not a natural stone, I would scrap the plywood and install 3/4" plywood with a face grade no lower than "C".....screw it down well. Now, install either a cement board like Durock or, if height is an issue, use Schluter's "Ditra" as a base for the tile. Either material needs to be "bedded" in thinset. The cement board needs to be screwed in as per Mfg recommendations. I like the Ditra....lighter, use a flat trowel to push it into a modified thinset bed like Versabond using a 1/4" trowel to spread it.

Fill the cavities with your flat trowel. The next day, tile away!
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mash74
Original Author
11 years ago
Thanks for the reply StoneTech. Yes, height is definitely an issue which is why I was thinking of going with the Ditra.
So you think I should definitely scrap the existing 5/8" plywood?
I was hoping to avoid ripping it out and then buying/cutting new plywood but it does seem like it's going to be pretty tough to get the existing adhesive off of the plywood.
I think if I left any of that old adhesive the bond between the Ditra and the plywood could be bad.
Thanks for the input, I think I'll rip out the old plywood tomorrow.
mash74
Original Author
11 years ago
Oh, and this is a ceramic tile.
Thanks
mash74
Original Author
11 years ago
Another question regarding the plywood, while in Home Depot I saw that they have tongue in groove sheets. Is this better when laying tile? Or are the regular sheets better?
Thanks
StoneTech
11 years ago
The T&G is probably a bit better, but I would put them in tight and then pull them out about 1/8".....also set them perpendicular to the joists and stagger the rows. Don't let four pieces all meet together. (+)