# Tile on slab /cracks



## DesPro (Nov 2, 2006)

Customer wants me to replace tiles in numerous areas where tiles have cracked mostly at door jambs. Cracks run diagonally from jambs and span 2-3 tiles, 12 x 12. The house was built on slab 12 years ago.

After removing the damaged tiles and thinset, what steps should i take to fill the cracks in the slab prior to re-tiling to ensure they do not re appear ? :001_unsure:


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## Ted W (Jan 7, 2007)

Start with a disclaimer, that you can't guarantee anything. 

When tiles crack like that it means there's some serious movement going on, causing the door jambs to crush down on the tiles. You can replace them, use a latex modified mortar adhesive, but the only thing you can promise the client is that they will eventually crack again. What's going on is a structural and, as a tiler or remodelor, it is not within your capacity to fix it.


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## R&D Tile (Apr 5, 2005)

If the cracks are even with each other, you will need a crack isolation membrane installed over all the cracks, then you can retile, if any of the cracks are uneven, one side higher than the other, there's vertical movement and the floor shouldn't be tiled.

Just curious, how wide are the cracks?, 1/4" or less I hope.


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## DesPro (Nov 2, 2006)

R&D Tile said:


> Just curious, how wide are the cracks?, 1/4" or less I hope.


All the cracks are hairline in the tile, but won't know for sure about the slab until I get things cleaned up. Aside from the membrane should I use some type of conc bonding caulk for the slab cracks ?


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## thom (Nov 3, 2006)

Cracks in slab-on-grade floors are not only common, they are the rule. Sometimes they crack through the tile, generally hairline cracks. Isolation membrane works. Unfortunately, it will raise the tiles a little so they no longer sit flush with the others.

I do a lot of tile on slab-on-grade, about 800-1000 sq ft on each house I build. I know there will be cracks and almost always hairline. That's life.

there is no perfect floor covering. Carpet?, Wood?, Laminate? Stained Concrete? Tile? They all have issues.


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## R&D Tile (Apr 5, 2005)

Yes, that's life, but cracking of the tile can be prevented by installing a membrane, and one should always be used over a slab, if not, and the tile cracks, the installer should be held responsible, or builder who hired him.

If the floor heaves, then that's an other issue, but there are ways to give tile a better chance of survival by taking a few added measures.

No one can guarrantee a concrete slab against anything, done hundreds of driveways and sidewalks with it, some last 20 years without a crack, some 2 weeks, too many things that can go wrong down the line from how it was batched to how it was installed.:w00t:

Done correctly, heights not a problem.


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## Bud Cline (Feb 12, 2006)

I would be curious to know what the door jambs have to do with anything. That slab doesn't know where the doors are and doesn't care. Why are the cracks occurring at the door jambs? 

I also don't see where it is possible for door jambs to "crush down" on anything. The jambs are attached to the studs and the studs rest on a sole plate, it would be the sole plate taking the strain to the subfloor. If the tile is in fact under the door jambs then the jambs have been undercut or installed after the tile but they are fastened to the studs and can't move downward without compressing the sole plates, so what's happening there?


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## DesPro (Nov 2, 2006)

Bud Cline said:


> I also don't see where it is possible for door jambs to "crush down" on anything. The jambs are attached to the studs and the studs rest on a sole plate, it would be the sole plate taking the strain to the subfloor. , so what's happening there?


Good point Bud. It does seem odd that most of the cracks are relative to the exterior walls. I will have to take a closer look. Thanks


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## Bud Cline (Feb 12, 2006)

Were it not for the menton of the cracks continueing on to adjacent tiles I would be more inclined to think that the tile had been cut around the door jambs, then tightly fit or tightly grouted to the door jambs. 

Each time the door would close (or slam) over a period of time undue stress would radiate into the tile from a door jamb (buried in tile) that would move slightly when the door was closed. Inside corners will always have more potential to transmit a cracking force into a tile that is being repeatedly tortured. 

Just a guess though.


Something else has just occurred to me that would blow my above theory.

Since you say the damage is at the outside walls I am now supposing that if during construction of the walls the sole plate was 'shot' onto the slab rather than being bolted onto the slab over time the shot-fasteners could cause the concrete to crack. Since each and every door opening would have a sole plate terminating on either side of the door opening, then stresses to the concrete from the shot on both sides of each door could be the culprit. This lack of bolts imbedded in the concrete would never pass inspection, if there was an inspection. Now I'm really reaching out there.


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## Bud Cline (Feb 12, 2006)

:whistling :whistling :whistling


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## Mike Finley (Apr 28, 2004)

Only thing is he says the cracks are 2 to 3 feet long going through multiple tiles. Sounds like the slab is cracked and heaved to me.


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