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Question:

Is it really necessary to use cement board when placing tile on plywood, like for a table top?

I am making a custom kitchen island and I planned to tile the top of it. The top of the island is going to be made of thick plywood for strength and I was told by the man at the hardwood store where I bought all the supplies that I needed to place cement board down on the plywood before I placed the tile down. I had bought a trim to go around the table top, hoping that it would be flush with the tile once the time went into place, however using the cement board makes the trim flush with the cement board and after the tile is installed, it would be about 5 mm taller than the trim. Do I really need to use the cement board? Would it be a bad idea to place the tile and mortar directly on the plywood?

Answer:

Use a slightly thinner plywood and glue it to the backer board. You will have adeqaute strength from the laminate and superior water protection from your backer board... The thicker plywood will find some use... it always does. If there is still any concern about table strength, redesign/ add to the table skirt (kind of like joists for a table top). why make it OK when you can make it great with a small amount of additional effort?
May 11, 2017
I've laid some tile, floors,showers, and a couple tables(more of the mosaic type). I'm pretty sure that you need to use hardibacker(cement board) only for showers or kitchen/bath floors. It's main purpose is to prevent any air /moisture from seeping up through the bottom ,thus causing the tiles to break. Hardibacker helps seal all that out. But I don't think it's mandatory for your project. You won't have to worry about spilled liquids after your table is cured and sealed. The grout is what keeps anything from getting under your tiles. Make sure you wait at least 24 hours before sealing your new tile job. Maybe check out a tile book from the library or look up How-to do -it Yourself type of sites for tips. Good Luck!
May 11, 2017
No, for your stated use cement board would not be needed. You can glue the tile directly to the plywood. Once the tile work is completed, wait a week then seal the tile and grout with a silicone sealer.
May 11, 2017
keep in mind that although ceramic tile may be impervious to water and other fluids, the grout between the tile is not. if there is a chance that something will spill with any regularity it will get through the grout and you could end up with mold. this is not a situation into which you want to place your family. there is a product called tilebacker board which is available in 1/4 thickness. moisture will still get by the grout, but it will not be in contact with the wood structure which of course is organic.
May 11, 2017
After multiple thousands of sq. ft. of tile, a simple, direct answer is... Plywood is OK/ Tile mortar will not seriously degrade plywood in the dry time. I suggest a poly based mortar and grout however since spills are possible. Steven Wolf
May 11, 2017

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