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I'd like to install slate tiles over a pre-existing plywood floor. The plywood floor is 3/4" and sits on joists.

There's a dip about 3/8" deep by 2 feet wide by 5 feet long. My plan was to fill it with self-leveling compound, before installing the cement backerboard and then the tiles. However, the guys at the tile store seem oddly negative about using self-leveling compound. Is there any reason not to? If so, what are my alternatives?

Tester101
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Drew Steen
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3 Answers3

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Yeah not sure I share their opinion. I did it 5 or 6 years ago and everything is still good. Just make sure that you use long enough screws in the area with the dip to hit the subfloor.

user359480
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Plywood is not the best substrate for self leveling compound. You can do it but for me its very ify.

I'll only put self leveling compound over plywood if the floor has zero to no flex, give, or movement in the subfloor.

Look at it this way if your floor starts shifting or moves every time you walk on it your leveler will flex and start to crack and break. If you are putting backerboard over the leveler then that is an easy answer: all the screws will just bust the leveler and will not work!

I would simply put down the backerboard with thinset under the backer board then screw, NOT nail it down.

Simply build your thinset up enough so your tiles will be flat all the way across your dip.

Piotr Kula
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ace
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The only thing I can think of is: what if your floor is mostly flat (except for the dip), but not truly level? Layers of thinset would allow you to build up the dip so that it's parallel to your floor. By contrast, leveling compound will dry level, but if your floor isn't level, that may not help you.

mikemanne
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