Marble tile

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  #1  
Old 01-07-10, 05:50 AM
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Marble tile

Just looking for "after the fact" information. Our church was built about 3 years ago, and in the main lobby at the visitor's center is fairly thin marble tile laid on the diagonal with squared off trim about 3' from all walls and entrance.
Someone noticed the grout cracking on a few of the tiles a few weeks back and mentioned it to the building overseer. He called me to look at it, but by now it has lengthened from the main doors to the back wall of the lobby.
At the middle, one tile was popped up more pronounced than others. I told him there was an expansion joint in the cocncrete below there, and the marble should not have been laid on it. He said surely not. I pulled the one tile which had loosened, and sure enough, an expansion joint.
My question, should the marble have been cut along the expansion joint, even though it was on the diagonal and an elastomeric grout line installed? I know it may not have looked all that good, but this zig zag grout popping has all the little old ladies upset.
Should the tiles be removed, cut at the joint and relaid at this late date?
 
  #2  
Old 01-07-10, 07:21 AM
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Larry

You cant just tile over a joint like that.

My understanding is that expansion joints(to allow for expansion and movement of the slab) and control joints (cuts in the slab to control cracking) are treated differently. You said expansion joint. Is that indeed what you have?

If its an expansion joint, you need to design the tile layout so that a grout joint lines up over the joint, then caulk that joint with a color matched caulk.

If its a control joint you can bridge the joint using an isolation membrane like Noble CIS and color matched caulk. Diagonal layouts are doable. See this link.

http://www.noblecompany.com/Portals/...ions%20ENG.pdf
 
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Old 01-07-10, 04:02 PM
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Thanks, Johnny. Figure 9 at the bottom of the page is what we have. I said "expansion" joint because it has opened to nearly 1/4". I can stick a pencil down in it. I figured a control joint would not be as large and opened. None the less the zig zag cracking of the grout has me wondering if the setting compound underneath may have slipped allowing just the grout line to crack. I am only going to reset two tiles after cleaning them and the concrete, and clean out the grout line and install an elastomeric type color sealant. Would that be a somewhat reasonable temporary solution? By no means is it meant to be permanent, as I know all the tile across the joint will need to be removed and the entire section reset over a membrane as you mention.
I appreciate the comments, and welcome anything else you or others can offer.
 
  #4  
Old 01-07-10, 05:40 PM
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Might be ok as a temporary solution.

Control joints are joints cut into the slab to control the cracking. It doesnt sound like thats what you have.

It sounds like you have an expansion joint there, and if thats the case, using a membrane wont solve this issue. A different tile layout incorporating a caulked grout joint over the expansion joint may be in order.

None the less the zig zag cracking of the grout has me wondering if the setting compound underneath may have slipped allowing just the grout line to crack.
I agree. This can sometimes happen with horizontal slab movement if the thinset bond is the weakest link. As you suspect, the slab movement could have just as easily cracked the tile.
 
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Old 01-08-10, 07:11 AM
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Larry

How wide is the crack in the grout? Got any pictures of the cracked grout and the joint in the slab?
 
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Old 01-08-10, 03:26 PM
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I was going over there today, but due to the snow they closed the offices. I'll take my camera Sunday and pull the loose tile and take a few pix of the area and post them. Actually the crack in the grout isn't appreciably larger than the others. The grout has just broken and as it is cleaned, it is sucked up and disposed of, leaving cracks.
 
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Old 01-14-10, 04:46 AM
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Follow up. Forgot to take camera and too stupid to remember I had my phone with me on Sunday, so no pix. I pulled the two loose tiles and it is definitely an expansion joint (slab on grade), and it was a good 1/2" wide once cleaned of tile setting compound. I think these two tiles had been replaced before, as it was not thinset.
Cleaned out all the zig zag grout lines with my Multimaster and applied color matching elastomeric sealant. Reset the loose tiles with setting compound on one side of the joint and elastomeric on the other side for a temporary fix.
They will definitely need to have all the tiles across the joint removed and laid properly with a surface expansion strip installed. I don't see any way out of it.
Thanks for the help and support.
 
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Old 01-14-10, 03:11 PM
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you are welcome. good luck.
 
 

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