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Unread 03-03-2016, 09:40 PM   #1
stimulu21
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Hairline cracks in grout.

Hello. I just finished a countertop today consisting of 6x6 porcelain tiles. I installed 1/4 cbu and used 1/8 spacing. Today was round 2 of grouting with mapei unsanded grout. I scraped all the grout out after the 1st installation because of the hairline cracks that showed up in a few spots. Also had some of the grout running right up along the tile began to crack. So after a bit of reading on these forums I was assuming the grout shrank a little bit. So for round 2 today I made sure to mix a bit dryer to be sure. I worked my nads off to ensure no voids were going to be a problem and really worked the grout in. Well within a couple hours I noticed the small cracks again so I tried to smooth them out. When I left it still looked kind of marbled in ,some spots along with a couple cracks. The guy whos house I'm working in likes to keep the heat at 80 - 84 and the vent is almost right over the countertop. Would the heat being on constantly have anything to do with these cracks? Thanks!
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Unread 03-03-2016, 10:52 PM   #2
Kman
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Welcome to the forum, Bob.

Sorry to hear about your grout problem, as well as working your nads off.

To answer your question, yes, the heat blowing right on the grout will cause it to dry prematurely and shrink, resulting in cracking. Other than turning the heat off, or redirecting it for a few hours, there's not much else you can do in that situation. I'm not sure it would help if you covered it with plastic to hold the moisture in.

What I would have done after the first round is switched to a sanded grout, which can handle the temperature a bit better than unsanded. Also, if there are any joints that are larger than 1/8", the grout will likely crack anyway.
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Unread 03-03-2016, 10:54 PM   #3
dhagin
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Hi Bob.

The heat alone shouldn't be a problem, but hot air blowin directly on the tile might be contributing. 2 other common contributing factors are mixing with too much water and cleaning with too much water. Sounds like you mixed OK - did you mix according to directions on the bag? - maybe too much water during cleaning?

If any of the joints are more than 1/8, then that could also be a contributing factor.

edit; looks like Kevin & I are pretty much in agreement.
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Unread 03-03-2016, 11:42 PM   #4
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Winter-time with high temperatures and heating often mean very low humidity levels, which may have made a difference. It wouldn't hurt to cover it with plastic to hold in any moisture, let the cement cure (and strengthen), while keeping the hot air blast from it. Personally, I'd try to block it off for at least 24-hours, if possible. The curing process will be speeded up with higher temperatures. Something like an epoxy, or one of the acrylic grouts may work better in this situation, but a cement based one should work.
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Unread 03-04-2016, 07:12 AM   #5
mistyinca
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Can I butt in here a moment? Kman, about anything over 1/8" cracking...our grout joints are 1/8" but we have a few that are 3/16" (the bullnose appears to be 1/32" smaller than the rest of the tiles and we had to put in a 3/16" grout joint every other tile to keep them aligned). I had planned on using unsanded because that's what you're *supposed* to do for 1/8" joints (though I prefer the look of sanded).

Should I be worried about cracking for those joints that are 3/16" (there's a small handful or 2 of them)?

Can I use sanded in the 1/8" lines?
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Unread 03-04-2016, 08:23 AM   #6
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1/8th or bigger grout joints push the limits of unsanded grout. Too much shrinkage and finish texture become a problem. With the newer performance grouts they have smaller aggregate sizes that allow the grout to be used from 1/16" up to 1/2" joints.
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Unread 03-04-2016, 06:51 PM   #7
jadnashua
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If the 'sand' (it's not always sand!) in the grout is small enough, you can use it in ANY sized grout line, it just gets harder when it is small. On the other hand, you're really stretching things and are almost certain to have issues with unsanded if the grout joint is larger than 1/8". Unsanded also is much weaker...the cement grows crystals, and if they can't interface with some rigid sand particles, their spikes can break, and if the mix isn't perfect and there ends up being too much moisture introduced, either in the mix or during cleanup, the cement particles can end up further apart, and when the moisture evaporates, leave the weak cement crystals with little to support them and crack or shrink.
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Unread 03-04-2016, 07:06 PM   #8
dhagin
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Jim.

Can you point to ANY grout specifically designed for use in ANY grout joint size? All the grouts I'm aware of have limits specified by their manufacturers.

Thanks.
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Unread 03-04-2016, 07:58 PM   #9
jadnashua
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Well, any is pretty broad, but Mapei's Ultracolor Plus can be used from 1/16" to 1" per their data sheet http://www.mapei.com/public/US/produ...lus_tds_ea.pdf and there are others. That covers a pretty wide range! Let's not be literal here...a grout joint smaller than 1/16" is probably unreliable, and won't be filled by any grout, so I think this qualifies for nearly anything most people might encounter.
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Unread 03-04-2016, 11:20 PM   #10
dhagin
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Stick to facts. 1/16 - whatever, is not "any". Many sanded premium grouts cover the 1/16 - 1/2 or larger range now. But you still need that full 1/16.

Stoners, I mean real pro stone installers, like going less than 1/16. It can be done, and various unsanded grouts will fill the joint.
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Unread 03-05-2016, 12:21 AM   #11
jadnashua
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In this forum, verses maybe the prof side, 1/16" is probably the smallest grout line achievable with good results...and, is the grout line design of many stone tiles per TCNA article here: http://www.tcnatile.com/faqs/40-grout-joint-size.html . An installer is free to use any size he or she feels comfortable with, but it takes very careful prep and execution and high quality tile to achieve joints less than 1/16", so the modern sanded grouts do cover the vast majority of situations. I know you have little respect for me, as shown on other forums...leave it rest.
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Unread 03-05-2016, 12:25 PM   #12
Davy
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Many times when installing marble where I'm shooting for 1/16 joints, the stone may vary a little and I may end up with some joints about 1/32. The unsanded will take care of these just fine.

It's always good to talk to the homeowner first about the grout. Not only the color but also if they are expecting sanded or unsanded. We need to talk it over if they select a 12x24 porcelain that I need to open up to 1/8 or 3/16 joints, especially if I get the hint that they are expecting unsanded. Epoxy, Fusion and Flexcolor CQ seem to have finer sand so I'll talk them in going that direction if I need to if they are expecting less texture on the grout surface.
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Unread 03-08-2016, 10:31 AM   #13
stimulu21
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Thanks for all the help guys. Well there was some spots here and there that had shrinkage. I'm fixing to do the back splash with grout and again will be using the unsanded grout. The lines are a lot smaller since it was a mosaic design with the netting on the back holding it together. Jumping in head first again bit this time I have better knowledge! Will post pics of finished product. Thanks again for all the help.
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