laying tile over plywood - thinset or adhesive?

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Old 06-02-14, 11:46 AM
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laying tile over plywood - thinset or adhesive?

I've done a ton of tiling in my time - floors, bathrooms, etc - but I've always done so either directly on concrete or (in the case of bathroom walls) backerboard.

Well right at the moment I've got a unique kind of situation in that I've just torn up some old linoleum (was that a crap job!) that had been laid on half inch plywood, which itself has been glued down over the original wooden floor. The lino was tough enough to tear up - the plywood isn't budging!

Now I know that the modern trend is to put down backerboard or some variant and lay the tile on top of that, but the problem is that a half inch of ply PLUS a half inch of backerboard PLUS the thickness of the tile itself is going to make for one heck of a threshold to the living room next door! I figure if I put the tile directly on the ply the half inch saving in height will make the threshold somewhat manageable at around an inch in height - any more and it becomes a natural tripping area for the unwary.

So with all that said and done, what's the technique for laying tile on wood? I'd guess it's the reverse of laying wood on concrete, right, meaning using a good adhesive instead of thinset? And being that it's being put down in a kitchen area, the idea would be to keep the gaps between the tiles to a minimum (1/8" gaps instead of 1/4" for 12" tiles) and using unsanded grout?

Thanks in advance
 
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Old 06-02-14, 01:34 PM
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You don't lay tile directly on wood, period. Floor concrete backer underlayment is only 1/4" thick, but you may be able to use Ditra as it is much thinner. Layer down thinset, lay in the Ditra and smooth it out. Thinset on top and tile. Lower threshold value all the way. If you do decide to decrease the tile grout joint, if it gets down to 1/8", do use unsanded grout, although you will have the option according to package instructions of using either sanded or unsanded.
 
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Old 06-02-14, 02:36 PM
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normally I'd go the sanded, but I figured with wood underneath (even with backerboard or whatever) the smart play in the long term might be to waterproof it as much as possible by using unsanded, just as a I would in a shower cubicle.

What the heck is Ditra? I'll have to look it up.


Thanks for the feedback. As I said, I've tiled umpteen houses in my time, but never one with a wooden floor.

You should see the tiling on the kitchen counter in this 50's house. I started breaking it up today as carefully as possible because I wan to keep the base cabinets in place. These days of course we use stuff like backerboard. Whoever did this job laid two layers of cement - with wire reinforcement - about an inch and a half thick - plus the tile! Now we know why the counter sits so high. I'm hiring a small jackhammer from one of the big box stores to try and break it up - easier on the cabinets than using a heavy hammer and chisel!
 
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Old 06-02-14, 05:57 PM
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Timbo59,

I agree with Larry. The best method is to install Ditra, which is only 1/8" total installed. 1/4" backer will be about 5/16" with the thinset under it.

But let's start at the beginning. We first wanna make sure your joists and subfloor system is adequate for tiles. Tell us the type and size of the joists, their species and grade if at all possible, the o.c. spacing and the unsupported span of the joists. Tell us what you've got for a subfloor. Is that 1/2" ply an underlayment?

Tile grout spacing, 1/8" maybe, but usually not. All depends on the quality of the tiles.

More on the thinset once we know what's going on. Hint, We don't say the "M" word when talking about ceramic tile floors or in wet applications.

Jaz
 
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Old 06-02-14, 06:47 PM
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As stated earlier, I've done countless tile jobs before, just never over wood flooring, so I'm well aware of the usual standards. So yes, I know 1/8th spacing isn't normal (that's why I noted it) especially with some of the poorer quality tiles that can be uneven in size. Try being less patronizing when making a contribution.
 
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Old 06-02-14, 06:58 PM
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Timbo, I am not sure of your last comment, but it may not have been called for. Jaz is one of the pros on the forum with probably the most experience in laying all types of tile. He was just making a comment that mastic is not used in wet locations since it practically never dries and will reactivate when wet and cause all sorts of problems.
We exercise a little brevity in our postings here, and I am sure there was nothing meant to demean you or "patronize" you. He will always ask you for the condition of your support mechanism, such as joist size, spacing and unsupported span. It comes with the territory to know all about your application that he can.
Just wanted to clear the air a little.
 
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Old 06-03-14, 12:04 PM
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You can lay over 3/8' min exterior grade ply (Fir ply is recommended though) Is it ideal? no but it can be done. The best advice is to lay over 1/8" Ditra but in some cases, you cant afford the extra 1/8"
 
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