leveling sub floor for tile

Old 05-01-01, 03:07 AM
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I have 5/8 ply sub floor over joists on 12 inche centers. The floor has some dips and I understand it should be as level as possible and 1.25" thick. I plan to put cement board over the ply 1/4" thick, but how do I level? What kind of product do I use. The tiles are 13" and expensive, so I don't want them to crack after installation. This is in the kitchen. I want to do this right. Marianna
Old 05-11-01, 12:09 PM
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RE: Level the floor


You are right in not wanting dips in the floor. Two things you can do. The first is the preferred method, especially if the floor is visibly uneven. Go to your local hardware store and ask for a self-leveling compound for a plywood floor, there are many brands that work well, I have no preferences except for self-leveling, and quick dry time. This stuff will work well, but keep in mind, it may raise your floor a little more than the cement board and tile already will, so use 1/4" cement board after this. Also keep in mind, that cement board isn't always flat, as is its nature, but after thinset is applied, it's unnoticeable (see the "beater bar" method below for this).

The second method, use the thicker 1/2" cement board and the thinset should help level out the rest. I would do this only if the floor after laying the cement board unattached doesn't deviate more than a 1/16" (even up to an 1/8" if using a thicker latex-based thinset) over the 13" radius of the tiles, which can be measured if you do your tile layout over the cement board before using the mortar. After a row of the tiles are set, use a 2' x 4' x 26" covered with some old carpet or several layers of newspaper over the tiles and tap gently with a rubber mallet or hammer to level the tiles. I've done this when someone is particular about the tile levels.

Good luck!
Lil Boy Blu

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