ceramic tile on concrete slab [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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01-21-2006, 04:54 PM
Hi everyone,
this is my first time posting here. I have a 330 square foot concrete floor I want to tile. I thought this would be easy but after doing some research, this might not be so easy. The concrete is uneven in several spots and has many small cracks. How should I approach this project and prepare the concrete?


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01-21-2006, 04:58 PM
Take a long straightedge and see how far out of flat it is. You may also want to know how far out of level it is, but the tile don't care (stuff might roll off of the table though!). Check each of the cracks for vertical vs horizontal movement - vertical displacement is much more of a problem than horizontal. How old is the slab? How big is the biggest gap in the crack?

01-21-2006, 05:04 PM
Hi Rick, welcome! Like Jim said. If the cracks are just surface and not vertical you will need some sorta membrane like Ditra to keep the cracks from coming through the tile.

01-21-2006, 05:28 PM
Thanks for responding so quickly. The concrete is 28 years old. I'm not concerned about level as much as i am about cracks, etc. The finished room I want to tile is only part of the entire slab. It was carpeted when i bought the house 7 years ago but the carpet was ruined be a broked washer hose. I want to do something to the floor to make it look nice. Some of the crack definately appear to be vertical. There is one small area by the door to the back yard that appears run un a loop starting and ending on the outside edge of the slab. some of the other cracks are very long and some are wider than others. What else do you need to know?

01-21-2006, 06:12 PM
From what I've read here (and it makes common sense), that vertical displacement means an unstable slab. Horizontal cracks are more likely expansion/contraction and while annoying, usually more stable. A horizontal displacement indicates something probably needs to be fixed prior to putting tile on it or it will likely fail over that joint (cracked tile and grout). One of the pros may offer some other insight and suggestions, but tile may not be in your future because of that problem...

01-21-2006, 06:24 PM
How can you tell the difference?

01-21-2006, 06:33 PM
Hi Rick, simple, is one side of the crack higher than the other? If it is that's a vertical crack.

01-21-2006, 06:39 PM
That's what I thought. If the vertical shift is small, should I be worried?