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robismyname 09-17-2010 12:28 PM

travertine flooring on concrete subfloor
Im about to embark on a flooring project. I will be placing travertine (honed and fillled) 18x18 on my kitchen floor. I live in Orlando,Fl and my subfloors are concrete. Moisture content was measured to be very very low. My house is about 5 years old.

My first area of concern is the fact that when I removed the old ceramic tile there was this black strip of sticky padding going vertically across the concrete subfloor. With great effort I pulled the sticky padding up to discover a vertical crack in the subfloor about 20 feet long, 1 foot wide. The crack width is about 1/8". I didnt know what that stuff was that I pulled up only to find out very recently that I pulled up the "crack isolation membrane" and it was placed there because when the subfloors shift it could disrupt the settlement of the ceramic tile and cause it to crack as well! So now I have to buy some new membrane and cover up this crack in the subfloor. I asked several people and they told me that cracking is natural. No one felt that it was sign of something wrong.

My concern is that do i have to place this crack isolation membrane all throughout the kitchen before I lay down my travertine in case there are some other cracks that may be coming soon? I really would hate to have tile cracking because my subfloor shifts and cracks a travertine tile.

I plan on installing engineered wood floors throughout the rest of the house. Where I am placing wood there was carpet. I found some hairline cracks here also. Should I lay down the membrane here as well?

My other concern is how do I bind/bind the tile to the subfloor? I saw one video that used some grey mortar and some white thinset. I then saw another video that used only white thinset. And another video where the guy called it thinset but it was grey in color and looked like mortar to me.

Any pointers are welcomed. I would lile to get this right on the first try.

oh'mike 09-17-2010 07:02 PM

I'll suggest some reading---Right here.-----Go to the flooring section,here and look for posts about Ditra.(use the search feature)

Bud Cline and Jazzman are the two most experienced with that product,however there are many others who know the product as well.

Ditra is an isolation membrane-designed for situations like yours---That seems like the answer to your concerns.--Mike---

JazMan 09-17-2010 08:12 PM

Hi Rob,

Thanks for the kind words Mike. :)

It takes a lot of guts to install 18" stone tile on a floor as your first installation, congrats for that.

Thin set and thin set mortar are the same thing. It comes in "dry-set" or unmodified, and modified. The modified version contains acrylic or polymer additives to enhance its performance and is required in certain instances. Both varieties come in white and gray color. White costs a little more and is desirable when installing light colored stone tiles. The color does not change the performance per se.

You will definitely want to install a crack iso on that crack, or a membrane on the entire floor. Although I use Ditra most of the time, this may be a job for NobleSeal CIS if you have expansion joints or control joints in the slab. CIS allows you to bridge the joints with the tiles so that it does not disturb the tile pattern.

Large tiles need a very flat floor, how flat is yours? Take a long straight edge or chalkline to calculate the "out of plane" in any 10 ft. length of the floor. Check many areas. The number you're looking for is no more than 1/4" out of plane in 10 ft. and 1/16" in 12". Actually for large tiles you would like within 1/8" in 10 ft. You may also want to consider using L.A.S.H. leveling or Tuscan leveling system to keep the tiles from drooping after you've set them.

Do some searching then come back with more questions.


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