Cracking grout [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile

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kldg
07-23-2001, 09:30 PM
I recently tiled my 10x12 office. This room was originally carpeted, and the floor was pretty squeaky. After pulling up the carpet, I pounded all the nails back down and put screws in here and there into the joists. That took care of the squeaks. The original subfloor is 5/8" T&G plywood over joists 16" o.c. I then added another 3/8" layer of plywood, which I screwed down to the first layer. Over that went a layer of thinset mortar, then 1/4" hardibacker. Then more thinset and my tile. I had the tile down for a while before I got around to grouting it. Now the grout's been down for a couple of weeks and I see some cracking in the grout alongside two tiles right where you step into the room from the hallway. I'm assuming this is from movement and I will have to fix this somehow. I do have access to the subfloor from underneath, and I wondering if adding some type of blocking in between the joists would prevent this movement? The cracking is parallel to the joists and is right in between two joists, so I'm thinking it is just dipping a tad, if that makes sense. Suggestions are appreciated!

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Rob Z
07-23-2001, 10:11 PM
Hi Kristi

Thanks for stopping by to see us.

Let's hope this is an isolated spot in the subfloor where support is lacking. Adding blocking under the area could help beef it up and provide stiffness for the subfloor. There could be other causes for the cracking grout, but let's try to firm up the floor in this spot, regrout the cracked joints, and see how it goes.

There are grout saws made that will assist in cutting out the old grout. You can find them at a tile store or at a place like Home Depot. The cheapies ( which will work fine for the small area that you are working on) cost only $5 or so.

What is the joist size and span under this floor?

Let us know how it goes.

rob

Bri
07-23-2001, 10:17 PM
Sounds like you went throught all the right steps..just a few questions.What size are your joists? 2x10? Did you nail or screw the hardibacker along with the thin set? If yes, it could be you just have two loose tile...tap on them to see if they're hollow. Your thin set could have skimmed over,before you got the tile down, causing a bond failure.

JC
07-24-2001, 04:23 PM
what kind of 3/8 did you use. Sometimes that stuff can have bad voids and be pretty crappie.

Also did you make sure to run the grain of the sub-floor across the joist.

Did you use mesh on the hardi seams?

LDavis
07-24-2001, 04:44 PM
If this is the only area of the floor where this problem occurs or persist, you may be able to isolate the "moving" tiles with a color-matched sanded caulk. This doesn't cure the problem, but it eliminates the visible result of the movement.

Obviously, if the problem spreads throughout the floor, this "quick fix" won't be practical.

John Bridge
07-24-2001, 05:08 PM
Since the loose ones are right in the doorway, isn't it possible they got stepped on? Maybe the bond has been broken?

kldg
07-24-2001, 07:04 PM
In response to your questions:
- the joists are 2X10's and they are 16" o.c.
- I tapped on the two tiles in question and I don't hear any different sound than when I tap on surrounding tiles. I'm not sure what a hollow sound would be like, though
- I did screw the hardibacker down at all the pre-printed spots, I used those special cementboard screws
- I also put thinset along and taped all the hardibacker joints with fiberglass tape
- I'm pretty sure that the thinset didn't skim over before the tiles were set there
- I'm also pretty sure that no one stepped on the tiles before the thinset hardened, I had the doorway blocked off
- I haven't put a threshold in the doorway yet, so I have a three dimensional view of the cracking grout. I don't see any voids in the thinset, from that edge anyway

So far the cracking is limited to the entire length between the two tiles right in the doorway, and the crack extends about 1/5 up between the next two tiles. The grout on the other sides of the two worst tiles seems fine. I'm thinking about putting the blocking up between the joists and waiting a while to see if the cracking get worse. If not, I'll take out the cracked grout and replace it. Does that seem like a good plan?
I tried to do everything right and I'm really bummed that despite all this work, I still have a problem. :-(

Bud Cline
07-24-2001, 07:20 PM
None of this makes any sense. Is this a test?

Before spending any more time and money here's what I think I would do: Mix a little more grout and regrout the crack(s) in question where is, as is. Don't remove anything, just go over what's there. Wait and see if it happens again. This has got to be a "fluke".

John Bridge
07-24-2001, 07:21 PM
Kristi,

Please don't feel too downhearted. The best of us have problems. I speak from experience. (Get it? Best? Experience?) :D It'll get straightened out.

John

Bri
07-24-2001, 07:23 PM
Is there a joint just under the tile in this spot? And did you stagger the sheets so that the joints in the plywood and the backer board didn't line up with each other? I guess you'll be able to see from underneath.
Brian

Rob Z
07-24-2001, 09:11 PM
Kristi

Don't panic yet. Do what Bud suggests and let's see what happens. It'll be quick, easy, and a good chance to procrastinate.

Keep us posted. It sounds like you've done everything right so far.

Rob

kldg
07-24-2001, 09:43 PM
Oh, I wish this was a test! Then I'd know the answer, right? ;-)
The crack doesn't fall right over any joint, but there is a hardibacker joint just two inches away, and parallel to the crack. However, as I was looking at it from the side, trying to see where all the joints were (subfloor, 2nd layer plywood and hardibacker), I realized that the crack actually extends into the thinset below the tile. So I'm thinking that this would definitely point to flexing of the subfloor in this one spot, rather than other causes.

Bud Cline
07-24-2001, 10:33 PM
The original subfloor is 5/8" T&G plywood over joists 16" o.c. I then added another 3/8" layer of plywood, Over that went a layer of thinset mortar, then 1/4" hardibacker. Then more thinset and my tile. I wondering if adding some type of blocking in between the joists would prevent this movement? The cracking is parallel to the joists and is right in between two joists,

kldg,
Two very important questions have been asked and I don't see where they have been answered: 1.)What is the joist size and 2.)do the subfloor joints coincide with one another?

This condition (cracks) you describe would be very very unusual if your structural conditions are as you describe.

And a crack in the thinset? Are you sure? How much did you pay for the thinset you used?

"OK, Is this really my mom"?

kldg
07-24-2001, 11:54 PM
Originally posted by Bud Cline

kldg,
Two very important questions have been asked and I don't see where they have been answered: 1.)What is the joist size and 2.)do the subfloor joints coincide with one another?

This condition (cracks) you describe would be very very unusual if your structural conditions are as you describe.

And a crack in the thinset? Are you sure? How much did you pay for the thinset you used?

"OK, Is this really my mom"?

[/B]

Bud,
The joist size is 2x10. When you ask if the subfloor joints coincide, I'm assuming you mean the layer of original 5/8" and the newly added 3/8"? If so, they do not coincide. I made sure of that when I added the 2nd layer. However, it's possible that the joints of the Hardibacker coincide with the original subfloor here and there, since they were covered up by the 2nd subfloor layer. But I can clearly see that at this cracking grout point, there are no joints in any layer. Now in the hallway just outside where my tile ends, I've ripped the carpet up there too, since we plan to put in new carpet once I have this tile issue finished, so it's bare subfloor, just the original layer. When I step heavily on the subfloor, I can actually see and feel the floor deflect. This is right next to my cracking grout. Perhaps this is contributing to the problem? This house is not particularly old (19 years) but it's not particularly well-built either. I don't think they used very high quality materials when they constructed this subdivision.

Yes, I'm sure there is a crack in the thinset too. I got down on the floor and looked at it from the side (remember it's bare subfloor in the hallway and I can see the build up of layers that I added, like a sandwich). The grout is cracked right alongside the tile, not in the middle of the grout joint, and this crack extends into the gray thinset that forms a layer underneath the tile. Now I did not remove all the thinset that oozed up into the spaces between the tiles when I laid each tile, but I did remove quite a bit. I can't remember the name of the thinset I bought, but it was around $20 a bag at Home Depot. I'm thinking it's something like Versaflex?? Actually, I bought two different kinds of thinset. I used a cheaper kind for the thinset that's between the hardibacker and plywood, and the more expensive kind for laying the tile.
Most importantly, if I said I was your mom, would you come over and fix my problem? :-)