marble tile question

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Old 04-21-07, 10:37 PM
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marble tile question

We have moved into a 10 year old home..the kitchen floor has Italian marble tiles, many which are loose. It appears on lifting them, that the grouting has cracked on the floor and yet has adhered to the back of the tile. It's gummy in spots on the tiles, and chalky on the plywood base. Any ideas on repair?
 
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Old 04-22-07, 05:23 PM
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I sounds like the tile was put down with mastic, not thinset. Mastic is no good for floors and should never be used in natural stone applications. Additionally, the tile should not have been set directly to the plywood. There should have been a cement backer board or isolation membrane used over the plywood. There is no easy fix here. The whole job was done wrong. Sorry.
 
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Old 04-22-07, 06:41 PM
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I don't see the issue with applying tile directly to plywood as long as the deflection measurements are fine. If the subfloor is sturdy, there should be no problems.

Apply the thinset with the flat side of the trowel first, working it into the plywood, then take the spacer side and trowel it.

I see plenty of homes, my parents for one, who have had tile directly applied to plywood for decades with no problems.
 
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Old 04-22-07, 08:28 PM
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re:marble tile question

Thanks for any and all information.. I'm not sure if I should go with redoing the floors or not, however. Any further thoughts? The area in question is about 600-800 square feet, and I can't buy any more of the tile if any of them break. Unfortunately we moved into the house with this issue.
 
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Old 04-22-07, 11:11 PM
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Russian : Johnny's correct. It sounds as if you've got a project on your hands. If I understand you correctly, the adhesive stuck to the tiles but came loose from the floor. It could be wall mastic as Johnny suspects and this would cause a problem such as you're experiencing. Since you're going to have to do SOMEthing with it, my suggestion would be to start pulling them up very carefully and see what happens. I've had to repair floors like that in the past and some times a guy gets lucky and they all come up undamaged. If they do, scrape as much of the adhesive off them as you can, clean them up, and then put them back down, after applying a good concrete backer board. Do not thinset directly to wood.

HotinOKC : Haven't you been following the discussions on this subject? Tile and wood have dramatically different expansion and contraction rates. Wood expands and contracts greatly where tile does so much less. Consequently, a medium between the two must be provided in order to compensate for the difference or the two materials can't remain adhered to each other. In my years doing floors, I have seen one or two exceptions where the tile was set straight to wood and lasted many years, but only a couple and I've never understood how they held up. I have also lost count of the number of floors I've seen come apart and need repaired due to the same thing. The ones that stay together are the exception and not the norm. Fastening tile straight to wood is a pretty sure recipe for a failed floor.
 
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Old 04-23-07, 05:11 AM
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Latex and polymer modified thinset mortars contain additives that provide the necessary bond and flexibility to permit many different types of tile to be directly adhered to plywood. The expansion and contraction differential between the tile and plywood are compensated for by these additives. There is a pervasive old-world mentality in this field that refuses to accept that new methods and materials can ever be as good as the old methods and materials.

As with any installation, the methods used must be appropriate for the materials being used. A solid plywood subfloor/underlayment combination is an excellent base for installation with modified thinset with NO cement board or other form of disconnect. Cement board, in particualar, is absolute nonsense in this regard anyway. Instructions are to use thinset and screws to adhere it to the plywood and then thinset is used to adhere the tile/stone/marble etc.
There is NO disconnect in this model as the cementious materials are still directly connecting the tile to the plwood! There is no "play" between the tile and the cement board and no "play" between the cement board and the plywood so you have not isolated the expansion differential between the two. Ditra, on the other hand does provide this disconnect and is a suitable material for certain applications
 
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Old 04-23-07, 09:33 AM
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Rockpro

A couple of things here. For starters, the thinset between cbu and plywood is not intended to bond the cbu to the plywood. The screws or nails do that. The thinset is used to fill any voids between the ply and the cbu and fully support the cbu. The reason for the cbu is in fact a better surface for the tile to bond to.

Yes you can set tile directly to plywood but there are some guidelines that you must follow. For starters you always need 2 layers of ply. TCNA says a 5/8" t&g subfloor and 5/8" exterior glue plywood underlayment. Leaving proper spacing for expansion, filing the expansion gaps with caulk, using the correct thinset, correct joist spacing etc. Lets just say that theres a lot to it, and if a diyer misses one single step, the installation is doomed. Lots of people do it wrong and get lucky. This person actually used mastic besides. I'll agree with smokey on this one. Installing to plywood for diyers is not a good idea. Lots of pros wont install to plywood either. Some will, some wont.

Diyers stand a much better chance of being successful with cbu or isolation membranes. Just my 2 cents.
 
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