Proper Thin-set for porcelain - Contractor Talk - Professional Construction and Remodeling Forum

dayspring · 04-26-2006, 05:11 AM

I have a few questions for you guys....

What would be the proper Thin-set for a porcelain slate tile applied to concrete floor?

What size notched trowel would be best?

Also, In general are the pre-mixed thin-sets any good and would you use them?

Thanks

R&D Tile · 04-26-2006, 06:19 AM

For porcelain use a good modified thinset that comes in a bag and you mix, NEVER use any pre-mixed products, they are all garbage, Mastic is the only one you can use, but not here and never on floors, only dry wall areas with 8x8 or smaller tile and never stone.

Size trowel depends on the backs of the tile, size of the tile and flatness of the floor, you always backbutter porcelain with the flat side of the trowel as well while setting.

What condition is the slab in, is it flat and no cracks, sealers or paint?

dayspring · 04-27-2006, 03:46 AM

I can't be to sure what may be on the floor, the building is 50+ years old. We took up glue down carpet. Glue is still on the floor. We plan to scrape it up. Thanks for the info on pre-mixed products, I've never used them before and now I won't. One of my employees wanted to use it, (LAZINESS) I suppose. The bath area I have to install tile on has commercial floor tile (like you see in wal-mart) on it, the larger area doesn't. Does it need to come up? Thanks for your advice!

Bud Cline · 04-27-2006, 07:38 PM

dayspring,

It is never a good idea to install ceramic tile over any vinyl products.

jjtt · 04-27-2006, 08:01 PM

I have had problems with thinset in the past not sticking well to porcelain tile. There is a specific thinset designed for porcelain tile that I highly recommend. I think the problem has to do with porcelain not being as porous as ceramic. Some latex additives can work as well. Talk to your tile supplier to find out the appropriate product for your particular tile.

Mike Finley · 04-27-2006, 11:34 PM

I use flex bond for everything that I can. Just installed some porcelain yesterday, stuff stuck so well it was a pain in the butt. This tile had no chamfered edges so it was like laying stone so I had to adjust for lippage every once in a while, those freaken tiles aren't going anywhere judging by how hard they were to pull up.

R&D Tile · 05-04-2006, 05:22 AM

All modified thinsets will work, you have to use the right size trowel and always backbutter Porcelain over 8" with the flat side of the trowel while setting for 100% coverage.

Oh, and never tile over any vinyl products.

Bill_Vincent · 05-04-2006, 09:01 PM

It's actually more a matter of the substrate, than the porcelain tile, as to which thinset you use. I've used unmodified (kerabond with water) to set over Ditra (several times) before with no problems

Eric K · 05-04-2006, 10:09 PM

What do you guys mean by "backbuttering flat"?? Smoothing mortar on the back? What does this do as opposed to just laying the tile on the mortared floor?

Bud Cline · 05-05-2006, 09:44 AM

Sometimes the backs of the tiles have depressed grids or waffleing or some kind of texture to increase bonding surface for the thinset and encourage a lasting bond. It is beneficial to fill these depressed areas with thinset to insure proper coverage. If you use the flat side of a trowel this will fill the depressions without causing the tile to stand-proud after the thinset is also spread on the substrate. The larger the tile, the more the benefit of this method. Useing the proper notched trowel to spread the substrate is also important.

ccoffer · 05-05-2006, 09:51 PM

Another method(my fave) is to just go ahead and use a bigass u notch and be done with it.

If you use a modified(you have to unless you are installing over Ditra) make it yourself by using regular thinset and admix. That is the best way. That does not mean a dry-spray polymer fortified won't work, it just is not as good.