tile over concrete - Contractor Talk - Professional Construction and Remodeling Forum

highlife77 · 12-05-2007, 12:13 AM

How do you guys prepare concrete slab for ceramic tile. I also have marble going over a slab. Basically i removed sheet vinyl and mosaic and cleaned /scraped up all the old mastic/glue. Floor is nice and level. Now I'm about ready to start setting my tile. I have set over concrete in the past but nothing that has had glue on it prior to install. I am just trying to do this right the first time and avoid future call backs. Thanks.

Jerry T · 12-05-2007, 07:46 AM

It seems like you are pretty well ready. But you should also check the slab to see if there is a sealer on it. Pour some water out in several locations and see if it gets asborbed.

Use the correct thinset for whatever type tile you are using. Is the tile a porcelain or standard ceramic?

highlife77 · 12-05-2007, 06:38 PM

ceramic in two rooms and marble in the foyer...no sealer, I already cleaned the slab with water it does not bead up as if there were sealer applied.

akraus88 · 12-05-2007, 10:38 PM

Nothing to worry about, if the concrete shows, just install on it, I would seal cracks with thin set before installation (which is not even necessary).

kevjob · 12-05-2007, 10:42 PM

no ditra?

fred lupton · 12-06-2007, 01:54 AM

If you have any cracks it is a good idea to apply something that will form an anti fracture membrane. When you bond tiles to a slab that is cracked and could move, the tiles will crack in exactly the same place. Use Ditra or Custom's Red Guard or Laticrete Blue 92 or something like this. If no cracks, probably no problem. If you have small cracks, Custom's Mega Flex setting mortar may be enough.

Bill_Vincent · 12-06-2007, 09:27 PM

Quote:

Originally Posted by akraus88

I would seal cracks with thin set before installation (which is not even necessary).

That won't do a thing for you. The microscopic grain to grain bond within the concrete didn't hold it together, what do you think thinset's going to do?

highlife, if there is no cracking in the concrete, clean it and go over. If there IS cracking, you first need to determine that both sides of all cracks are even. If one side is higher than the other You can't tile it. There's not a membrane made, including Ditra, that will protect the tile from vertical movement. If the sides are all even, you have one of two choices. You can either go with a crack isolation membrane, which just goes over the cracks, or you can use something like Ditra, which covers the entire floor.