Old 10-30-12, 07:37 AM
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I'm new to this forum, hoping to get some advice. I'm planning a tile installation in a small bathroom. Just removed vinyl and old parquet flooring. The subfloor consists of tongue/groove 1 by 6 boards installed diagonally over the joists and 1/4 inch plywood over that. The plywood is nailed down with a zillion ring nails. Wondering if I apply thinset and 1/2 inch cement backerboard over the plywood if that will be enough. Total thickness would be 1.5 inches including the backer board. Or should I rip up the plywood and install 1/2 inch exterior and the backerboard? thanks
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Old 10-30-12, 07:46 AM
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Welcome to the forums.

What you have will not suffice but let's start further down - what's the size, spacing and unsupported span of your floor joists?
Old 10-30-12, 11:31 AM
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And the plywood must come out.
Old 10-30-12, 03:11 PM
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Depending on our answers to Mitch's questions and after you remove the luan, a layer of 1/2 or 3/4" plywood may suffice. Concrete backer underlayment offers no support, so take that out of the equation. On floors you will most likely only use 1/4" cbu anyway, so see how that figures in your scheme.
Old 10-30-12, 03:15 PM
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Put your headphones on, time to pull some nails. We all have been there. The luan is not stable enough to be included in the base for eventual tile, it delaminates too easily.
Old 10-30-12, 06:30 PM
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We're still waiting for the framing info from Jim (?)

We all agree the 1/4" ply is doing no good and needs to be removed. We agree you need to add some structural underlayment grade plywood, but how thick? I do not recommend 1/2", too thin. Use min. 5/8" or better yet 3/4" if possible. You can make up for the extra thickness by using 1/4" or 5/16" concrete backer or better yet you can use Ditra instead which adds a total of 1/8" including mortar.

Old 10-30-12, 06:42 PM
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Thanks to all of you. The joists are 2 by 10. 16 inch centres. The span is 10 feet. Thanks
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