# Proper thinset and thickness



## JazMan (Feb 17, 2007)

Hi Dennis,

OH, OH, kinda too late for that now don't ya think?:whistling2:

In addition to the points you asked, there are other subfloor requirements, especially with natural stone tiles on floors.

First your questions. Aside from preparing the wood subfloor, thin set is spread with a 1/4x1/4" notched trowel for the concrete backer. This adds about 1/16". Tiles are installed using modified thin set. With 18" stone a 1/4x3/8x1/4 should be fine. Even a 1/4x1/2x1/4". Some would use a 1/2x1/2". Since the tiles have flat backs, the larger trowel should not be necessary. The bond coat adds 3/32-1/8", unless a special mortar was used. 

With large heavy tiles a medium-bed mortar is recommended, there are many possibilities. It would be easier if you just told us how the installation was done and with what specific products.

Back to the special specs for natural stone tiles. The joists and subfloor system should meet L720 deflection specs. Standard home construction generally meets L360 specs. If you install natural stone on a L360 floor you'll end up with more pieces than you first installed. Not good.

Tell us the; type and size of the joists, their species and grade, their spacing, the unsupported span to the inch. We can tell you if they meet specs. 

Also, for natural stone you need a double layer subfloor totaling 1 1/4" thick, installed properly.

Jaz


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## Bud Cline (Mar 12, 2006)

WHOOPS...I must type slower than Jaz.

Travertine (a natural stone product) requires a floor structure that is twice as strong as that required for ceramic tile, and a double layer of subfloor is required. Ceramic tiles require a floor-structure deflection rating of 1/360 while travertine requires 1/720. That's your first concern when installing travertine tile. Most-often a typical (older) wood floor structure will not handle the deflection requirements needed for a travertine installation. Even a lot of newer structures will not conform since they are built to minimums most of the time and minimums don't get the job done.

Any thinset mortar will work with travertine, either modified or unmodified. There are also thinset mortars designed for stone tiles. Typically travertine is light in color and a white mortar is used.

There is no required thickness of the thinset. The thinset thickness is determined by the size of the trowel used and the size of the trowel is determined by how the back of the tile is constructed and the size of the tile. In the case of travertine the back of the tile is smooth so a larger notched trowel wouldn't necessarily be required. With any tile spread-coverage of 85% is the recommended coverage rate but one should always strive for 100% coverage.

All cement boards are to be set into a fresh bed of thinset mortar (no other product is acceptable) then, mechanically fastened to the substrate. Typically a 1/4" X 1/4" X 1/4" notched trowel is recommended for the installation of the cement board.



> Are there standards ? Actual approved guidelines ?


Yup ! There are !
*The Tile Council of North America* (TCNA) sets forth minimum standards in their "*Handbook For Ceramic Tile Installation*".
In addition...travertine also comes under the guidelines recommended by *The Marble Institute of America*. They also publish recommendations. Then there is ANSI (*American National Standards Institute*) which has more to do with the testing of the prescribed methods and products of the industry.

So hey.............Why do you ask?


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## Bud Cline (Mar 12, 2006)

Same guy, same topic, different thread:
http://www.diychatroom.com/f5/installing-travertine-floor-tiles-107331/#post665388


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## DENNIS R (Jun 11, 2011)

I would like to thank everyone for their replies as this is my first time every using the site.

I am not an expert and have counted on my contractor to do the right thing but have been finding mistake after mistake..This conversation is well above my level of understanding. The floor was installed already and the issue was having a few cracked tiles and it wasn't sealed and finished properly. The contractor is meeting on Monday morning to discuss next steps. He will replace tile if he is at fault but I need to know how to even determine that.

Here is what I know

3/4 inch wood subflooring
another 1/2 added as I felt the old area of the room was weak.
cement board- 1/8 " mapei keraset tile mortar
heated floor system- 1/4' mortar-same as above
1/2 mortar- same- tile
I don't know if the wood subfloor or cement board was screwed in any particular distance apart.

The old floor section experenced the cracked tiles so far.


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