Travertine tile question

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Old 11-19-06, 08:44 AM
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Travertine tile question

I have purchased 12"x12" travertine tile to lay in my 2nd floor master bathroom. I have a 3/4" plywood sub floor with engineered truss support underneath. I have already layed 1/4" hardi backer board over the plywood sub floor and it will not be possible to remove this without a lot of work. Can I install a layer of Schluter ditra membrane in thinset and lay the travertine over top? Will the sub floor be strong enough or do I need to return the travertine and think about purchasing a different product?

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Old 11-19-06, 09:11 AM
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Michaela

You may be able to do ceramic tile over what you currently have but definitely not travertine. All natural stone installs need minimum 2 layers of plywood which you dont currently have. Additionally, its not likely that your trusses meet L720 deflection which is required for natural stone. You would need to check with the truss manufacturer to make sure though.

Although 1 layer of 3/4" plywood subfloor meets minimum for ceramic tile it is in fact the bare bones minimum. Installing more plywood is always recommended. The hardi does not add any strength to the floor. It merely serves as a substrate that the thinset will bond to. Ditra over the hardi wont allow you to install natural stone and will be of little benefit even for ceramic tile in your current situation. Normally you use a cement board or a membrane like ditra but not both.

Its likely that what you currently have will be ok for ceramic tile though. They do make some very nice porcelain travertine look-a-like tile these days. It is extremely durable on floors as well and is something you may want to consider.

Did you bed the hardi in thinset before you screwed it down. Its required, and your floor will likely fail if you didn't. Also you dont say what the on center spacing is between the trusses. Backer boards have on center spacing limitations and the on center spacing of trusses often exceeds those limitations.
 

Last edited by HeresJohnny; 11-19-06 at 09:24 AM.
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Old 11-19-06, 12:43 PM
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I didn't install the hardi in mortar so I guess I'll have to pull it up and redo. The engineered floor joists are 22" on center. If I put another layer of 3/4" plywood on top of the existing 3/4" plywood, would that have enough structural integrity for the travertine. I am trying to determine the least amount of work as I've already purchased the tile and it sounds like I need to unscrew all of the hardi backer anyway.
 
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Old 11-20-06, 08:28 AM
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Michaela

Before you can determine if you'll be able to install travertine you need to find out if your trusses meet L720. You'll need to contact the manufacturer of the trusses, tell them what size they are (they should have markings on them to indicate this) what there on center spacing is and what there unsupported span is. My experience is that the trusses are usually sized to meet L480 not L720 so unless the builders knew you would be installing natural stone on that floor you probably dont meet L720. The manufacturer of the trusses will be able to help you with this though. As to the spacing of your joists, Hardibacker cannot be used on joists with o/c spacing of greater than 19.2", so you cannot use the Hardi. I saw it mentioned somewhere that 1/2" wonderboard can be used on spacing up to 24" but Im not positive of this so you may want to check it out. There are also membranes that can be used in your situation instead of cement board.

Additional layers of plywood help with deflection between the floor trusses, but do not help with deflection along the length of the trusses which is the problem you need to overcome. If you go with a porcelain or ceramic, you only need L360 which you probably already have. Floor framing for natural stone products needs to be twice as strong as ceramic products.

Sorry but yeah you need to remove the Hardi, and you wont be able to reuse it.
 
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