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-   -   OSB + Plywood = solid base for tiling? (http://www.diychatroom.com/f5/osb-plywood-solid-base-tiling-143921/)

Denisrus 05-16-2012 02:26 AM

OSB + Plywood = solid base for tiling?
 
I know it's kind of old topic but...
I have 19/32" OSB subfloor, on top of it I put 3/4" plywood. I used glue and hundreds of screws to build proper base for tiling the floor in one of my bathrooms. I did the same in the other one and now it's been over a year, no cracks, the floor is solid. My bathrooms are fairly small and require one or less than one sheet of plywood. I used Acrylpro ceramic tile adhesive from Home depot. Later I read a lot about tiling over plywood and now I am really concerned about it, plus the plywood I used is not exterior grade.
Should I do the same in the second bathroom? I don't think its a good idea to rip off the plywood as it is glued and screwed to the subfloor.
I am just about to start tiling and have all tiles precut and ready to be installed. Do you have any ideas on what I should do?
Thanks a lot!

Bob Mariani 05-16-2012 12:11 PM

Sub floor is fine, but add 1/4" cement board. Do not tile over plywood!

joecaption 05-16-2012 12:15 PM

It should have been 3/4" subfloor rated, which would be ext. glue and no voids.
When adding underlament it does not get glued, just screwed.
There needs to be a thinn set under the 1/4 tile board spread out with a 1/2" toothed trowl.
It serves to fill in the small voids in the low areas between the floor joist.

Denisrus 05-16-2012 05:07 PM

Quote:

There needs to be a thinn set under the 1/4 tile board spread out with a 1/2" toothed trowl.
It serves to fill in the small voids in the low areas between the floor joist.
1/2" toothed trowel sound too big to me. Would it be just enough to level the floor with a flat side of a trowel to fill the voids?
Once I set thin set, I can intall 1/4" Hardi-Backer board right away, can't I?
Do I have to use special type screws?
How long does it take before I can start installing tiles?

JetSwet 05-16-2012 07:10 PM

What type of 3/4 ply did you put down? Joe is right about the 1/2" for tile board. Are you going with the cement board or are you going to tile on the ply?

Denisrus 05-16-2012 07:21 PM

typing mistake

Denisrus 05-16-2012 07:22 PM

typing mistake

Denisrus 05-16-2012 07:23 PM

I have 3/4", non exterior grade. I looked up in hardie backer instructions and they say a 1/4" trowel should be used. But they also say the plywood should be exterior grade.
I will put 1/4" cement board and then tile.

oh'mike 05-16-2012 07:35 PM

Okay, everyone--reread his (her) post---

The glue is not needed between the OSB and the plywood---

You may have used exterior glued ply--it should have a grade stamp that will say something like"

3/4" BC
exposure 1. (exterior glue)

Or "3/4" CDX" (X + exterior)

Next--the 1/4" Cement board--1/4" trowel is fine-(I often use 1/4 x3/8)-set into a bed of fresh modified thinset--Then nailed with roofing nails or screwed with alkali resistant screws.

Last --the mud you used--wrong stuff,if I am not mistaken,Isn't AcriliPro a premixed mastic?
Should be a powdered modified thinset---
Mastics are water soluable and will re emulsify when exposed to water--(leaking toilet--shower curtain loose--)

Also--mastic needs air to dry ---with a big old tile covering the wet mastic,this could take months.

Ceramic tile can be set over exterior grade ply when using a good powdered thinset--
While not the ideal surface like Durock or Wonder Board--it will work most of the time---Mike---

JetSwet 05-16-2012 08:07 PM

The op can tile right over sanded cdx or sanded Bc ply although not recommended by most here.

Denisrus 05-16-2012 08:44 PM

1 Attachment(s)
Well, I can't see stamp on ply wood of any kind of grade, maybe on the other side?!?
AcrylPro is premixed mastic.
I will install 1/4" hardiebacker and then tile, however my floor willl be at least 1 1/2" above the subfloor. Plywood 3/4" + cement board 1/4" + tile 1/4" + thin set x 2 = approx 1 1/2".
I will have to come up with some way to have a transition between hardwood and bathroom floor.

Denisrus 05-16-2012 08:48 PM

Is it normal to have such a bathroom floor to subfloor difference (1 1/2")?

Denisrus 05-16-2012 08:53 PM

Would Ditra or Schluter membrane do the same as cement boards?

oh'mike 05-16-2012 09:00 PM

It's not uncommon--you went a little over the top with 3/4" ply--1/2" would have been fine--
That ply looks like BC exposure one,by the way--so you do have exterior ply--

A wood reducer at the door will give you a nice look--If you have a table saw and a router you could make a custom one that will be the same thickness as the tile--

Please use a powdered modified thinset---the premixed bucket mixes often cause trouble--and thinset is less expensive---Mike--

JetSwet 05-16-2012 09:03 PM

Quote:

Originally Posted by Denisrus
Well, I can't see stamp on ply wood of any kind of grade, maybe on the other side?!?
AcrylPro is premixed mastic.
I will install 1/4" hardiebacker and then tile, however my floor willl be at least 1 1/2" above the subfloor. Plywood 3/4" + cement board 1/4" + tile 1/4" + thin set x 2 = approx 1 1/2".
I will have to come up with some way to have a transition between hardwood and bathroom floor.

Well so much for your pattern that was marked out, that looks like unsanded ply to me to many knot holes.

Since your questioning the hight use 1/4" trowel so it's not that high when u place the cement board.

Screw your boards with backer on screws and mesh tape the seams with thinset.

A Marble saddle for door is what you will need.


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