Tiling over plywood question [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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Marko F
09-19-2001, 12:34 PM
I recenlty installed a 5/8" layer of exterior grade plywood over another 5/8" layer of plywood on the joist in a bathroom (16" O.C.)

I am planning on tiling over the plywood. When I lay out the tilews to get a good baseline some of the tiles can be slightly rocked back and forth. The floor is pretty level. Is this common? Will a latex based thin set like "Single'Flex" correct the problem when the tiles are put in?

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09-19-2001, 01:05 PM
Since you already have the plywood down, you should use the best quality thinset you can get. Plywood isn't the best subfloor for ceramic,but the good thinset will stick to it quite well.

note to self: other guys on forum should be yelling at me any minute now...disconect modem.


John Bridge
09-19-2001, 04:17 PM
Hi Marko,

The reason we don't like plywood is because it's not really stable dimentionally. It can shrink, swell and otherwise move around.

Bri is right, though (I ain't gonna yell at him). If you're going to do it, use Super Flex or something like it. The sack will cost you between $25 and $30 American (maybe $150 Canadian).;)

09-19-2001, 06:41 PM
Hi Marko,

If you're gonna install over plywood(which is not cool by the way)at least try to prevent the perimeter of the sheet from moving.This is where tile over plywood jobs are most likely to fail.Buy some 1 1/4" floor screws and screw these about half inch from the edge spaced about 3" apart.And 6" apart in the field.

09-19-2001, 07:47 PM
Thanks for all the advice guys, I knew I would hear it about not using cement board. Maybe I will, I just didin't want to build up the floor another 1/4". Can someone tell me a little more about this "Ditra" for going over plywood. What is it, where can I buy it, how much will it build up the floor?

Thanks Again for all the help!!

09-19-2001, 07:52 PM
Ah..Ditra...Here's a link..read all about it!



Marko F
09-20-2001, 10:23 AM
Thanks for all the Ditra info. I finally found a tile distributor about 50 miles from my home that had a roll of Ditra. It isn't very common around here at all. I'm going to use it in 3 bathrooms a foyer and a landing. Are there any special tricks I should know about? It is applied with a regular thin set, correct?

09-20-2001, 12:40 PM
It's applied using good quality polymer modified thin set...not much of trick to it..you can precut everything...then spread the thinset with the reccomended notch trowel and install the Ditra. Make sure you "rub" it down well with the back of the trowel to make sure you have good contact with the subfloor. Once it's down you can lay the tile immediatly. Just remember you'll need extra thinset to fill all those waffles in the ditra..so buy more than you think you'll need.


Marko F
09-20-2001, 12:46 PM
Thanks Bri,
Although I'm not sure what you mean by "rub" it down?

John Bridge
09-20-2001, 03:57 PM
He means press if firmly into the thinset with the flat trowel to make sure it's adhered well.