Travertine Underlayment

userbobMay 21, 2012

Hi, I am going to be installing a travertine floor in my bathroom. Here is a diagram of my current setup. On top of the joists (16" OC) sits 3/4" plywood sub-floor. On top of that are 3/4" thick furring strips (builder loved this technique for some reason). On top of the furring strips is another layer of 3/4" plywood. This is what the current tile is installed on and they are popping right off, making demolition pretty easy.

My question is can I install my travertine tiles (12x12) right onto the plywood or do I need yet another layer for an underlayment. I will be installing radiant heat as well. I'd rather not have to put down another 3/4" thick board to get to the 1-1/8" thick recommended underlayment thickness for travertine if I can avoid it. Is this setup strong/flexible enough?

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First, you need to remove the upper plywood layer AND the furring strips. There is entirely TOO MUCH "flex" in that structure. Now, re~attach the plywood perpendicular to the original plywood, without glue. Overlap the intersections and try NOT to screw it into the joists.

At this point, the deflection should be at or less than L 720. This is what you want. Having said that, attachment to plywood is tenious, at best. Tile Pros can and have done this, but we don't recommend it/ Plywood and morter don't "play well."

Install either 1/3" or 1/2" Durock over the floor. You need to set thinset with a 1/4" trowel, mixed very soupy and screw it down immediately as per manufacturer's recommendations. You should also either spray or sponge water on the cement board before setting it as it is VERY thirsty and tends to draw moisture out of the morter prematurely. You are now ready to tile.

Alternatively, you can use a material such as Schluter's Ditra XL to the plywood with a modified morter and tile away.

Either of these processes add, not only a good base to tile upon....they also give you an "Uncoupling Membrane" that should preclude any further cracking problems.

More information on the Schluter product can be viewed at their website.

This will give you a trouble-free floor.

Hope this helps.

    Bookmark   May 26, 2012 at 5:56PM
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Hello. Anyone Home? Did that answer your question???

    Bookmark   May 30, 2012 at 6:48PM
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Sorry, got caught up on another portion of this bathroom. What I'm going to end up doing is this (from basement up):

Existing sub-subfloor
3/4" plywood screwed down (not to the joists, 90 degree orientation)
1/2" plywood (OSB) screwed down to the 3/4" plywood
Layer of thinset
1/4" backer board (Green E-board, used it in the past with great results)

I should note that my original picture is a little off. My furring strips are currently only spaced about 6" apart from each other, not the 16" as shown. This is one of the few floors in our house that seems to have no movement already. I have to believe that my proposed setup (based on your recommendations) will be rock-solid.

Thanks for the help!

    Bookmark   May 31, 2012 at 10:49AM
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I might only add that the folks at the John Bridge Forums have pointed out that the second layer of plywood can, indeed be parallel to the first, as long as both sheets are perpendicular to the joists. Again, there should be at least a 1/3 "overlap from the first to the second.

You still will need a CBU or Ditra on top of everything for proper bonding to the tile. Best of luck!

    Bookmark   June 2, 2012 at 5:00PM
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