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Discussion Starter #1 (Edited by Moderator)
I recently started a bathroom remodel, first time attempting such a job, and was planning to put 12x12 ceramic tile down for the flooring.

After stumbling on to this forum, and reading a couple threads, I noticed the mention of "deflecto calculator", so I looked it up and used it.

According to the calculator, I have a deflection of L231, with 12ft 2x8 Joists of unknown wood, spaced 16" apart... which is a no go apparently for everything but wood and sheet vinyl.

Is there anything I can do to make the room acceptable for Ceramic tile, or am I stuck with the aforementioned wood or vinyl? Are there any other possible variables that may shift this in my favor, the idea of putting vinyl back down is quite a disappointment.

Thanks in advance.
 

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Doer of Many Things
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Basically you either sister in new joists alongside the old ones or you install a beam with proper support that runs under all the joists to effectively cut your overall unsupported span down.
 

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I've laid a lot of tile on 2x8 douglas fir floor joists spanning 12', 16" oc with 3/4" OSB sheathing, then 1/2" denshield. And I will continue to do so.
 

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Tileguy
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Cmas55,

Your ratio might be a little better if you knew the species and grade. The calculator is a bit conservative. But you are a little below spec regardless. Chances are you could still get away with it, but no guarantee. Too much deflection along the joists is much more forgiving than deflection across the joists. (too thin or wrong subfloor sheet (s)).

You should stiffen the joists if you can. You might also look for a premium thinset called Reflex made by Hydroment. They claim success even at L240, (they, not me). It's not available in all regions though. (Another reason you shoulda listed where you are).

Jaz
 
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