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diy'er on LI 09-07-2009 08:01 PM

help! why do the tiles in my bathroom crack?
this has been a major problem for years.

our powder room is on the first floor in the middle of the home. (It is on a concrete slab... no basement beneath.) in the early 80's, terra cotta tiles were installed throughout the (very large) hallway/foyer and in the adjacent bathroom by a professional. While most tiles are still fine to this day, a crack developed from the hallway, through the doorway and into the small bathroom.

On 2 seperate occassions, the tiles were chizzled out and replaced with new terra cotta. I believe the 2nd time the tile guy may have placed a mesh under the grout of the bathroom tiles to help prevent tile cracks.... In the end, the tiles always cracked again in the same spot.

For years we gave up and left the cracked tiles as-is. Now, we're remodelling the entire powder room and would like to replace the floor (with porcelain 12x12 tiles). Obviously, we need to figure out what causes the cracks so the new floor isn't trashed within a year.

Please, if anyone has ideas what could be causing this, toss ideas my way!!! We desperately want to avoid another cracked floor! (My father-in-law will be laying all the new tile (he's bored and we're grateful!), so we can easily demo the old floor and check the slab for specific things that you may suggest)

thanks for your help!

ps- I should add that the crack is roughly 6 feet long, and runs on a diagonal across the floor

Bud Cline 09-07-2009 08:58 PM

Has nothing to do with the tile. The substrate is not suitable for tile.

Sounds like Texas!

Are the cracks at different elevations from side to side?

Is your slab a "post-tension" slab?

There are ways to accomodate some of this problem but they may not be totally effective in all cases.

What type of soil is around your home?

Describe the landscaping.:)

What is the elevation of your home in relation to other homes in the neighborhood?

diy'er on LI 09-07-2009 09:34 PM

coming from the tile guru, that's depressing news :(

what's a post-tension slab? The home has a partial basement (under the eat-in kitchen)... the dining, living, and family rooms are all on slab.

well, it's a large home and foyar... I think the tiled foyar is something like 50' by 20'? there are no cracks except for this one.

The front yard is a reaonably large hill (with the home on the top of the hill), and the backyard has numerous slopes.... with an overall very slight slope towards the house (we're regrating next year so we can flatten it out, budget permitting). The home to the left of us is a bit higher than us and the one to the right is a bit lower (both fairly far away... over 100 feet)

the soil is fairly clay-ish, but we never have pooling water anywhere in the yard. We live in the center of western suffolk county.....

Do you think there's any way to work around this problem so we may still have the gorgeous porcelain tiles we picked out (didn't place order yet)?

oh, and I have to go check the tiles in daylight to see if the cracked halves are at different elevations. upon initial inspection, I think they're not. they're only cracked.

Bud Cline 09-07-2009 09:49 PM

HOLD ON NOW, it's not the end of the world just yet!!!

OK, based on your "partial basement" comment it isn't likely you have a post-tension slab so we can eliminate that as an issue.

Living on a hill helps some but keep in mind your landscaping has everything to do with the health of your structure. It is most important to keep water away from the foundation. You need to get rid of any gradation that slopes towards the house.

Now since you know your soil is clay we can start there. I was hoping that wasn't the case. Clay is like a sponge. It absorbs water easily and when it does it expands with great forces. It is safe to assume that may be the cause of the crack to begin with. Water coming towards the foundation surrounded by clayey soil isn't good.

I'll bet if you correct the drainage issues you will stop the slab movement for the most part.

Now the tile.

There are isolation membranes that will allow the slab to move under the tile to some degree. They will even allow that crack to open and close slightly with the seasons if it is still a living crack and from the sounds of things it is alive and well. There are also flexible tile adhesives that will accommodate some movement.

The biggest thing right now is the question you didn't answer.
Is the crack the same elevation on both sides of the crack or is one side higher than the other side?:) If the slab is moving up and down you're sunk for now. If the slab is only moving laterally when the crack opens and closes you may be OK with a membrane.:yes:

nap 09-07-2009 09:52 PM

I am not trying to step on buds toes. I am definitely not a tile guru but anyway:

if the crack is not different elevations on each side, it is better than if one side has risen or the other lowered.

bud; where is am working, they are laying quite large tiles (up to 2 ft X 3 Ft I think, maybe bigger). They rolled on a black rubbery coating before mud and the tile. They told me it is used to isolate the tiles so they would not move with the floor and you should not have the cracking problems becuase when laying a tile over a crack, the tile is not adhered to the floor so tightly as to cause the tile to split when trying to follow both sides of the crack.

I haven't seen it before (but I am not a tile setter so it could be a million years old) but the theory makes sense to me.

cocobolo 09-07-2009 09:52 PM

By your description of the crack, it almost certainly seems not to be the fault of the tiles.
You mention clay, this possibly has something to do with the cause of the cracking.
It is entirely possible that the concrete beneath your existing tiles has cracked, and is moving just enough to crack your tiles.
It may be related to a drainage problem around the house, wherein water is getting under the slab somehow during the rainy season - if you have one - and possibly expanding the clay a small amount. Then shrinking again in the dry season. That's purely a guess.
How old is the house?
Have you asked your neighbors if any of them have a similar problem?
Since this seems to be a recurring problem, it appears that you will need to do as much checking as you can into that slab.
Is there any possibiity that you have a plumbing leak which is introducing water onto, or immediately beneath the slab anywhere near that area?
Things to think about anyway.

cocobolo 09-07-2009 09:55 PM

Sorry about that - I was writing while the last two posts were being put up!

diy'er on LI 09-07-2009 10:22 PM

right now, I'll say that from your descriptions I *think* it's a lateral shift... I will post an update tomorrow. The lighting isn't very good down there, and I don't really trust my "feel-around blindly" diagonistic.... but it doesn't seem to be different heights.

and this problem entirely COULD be due to the clay soil :mad: (hate that freakin' clay and my hilly yard! We're definitely regrating... either next summer, or the following year... it will be a HUGE expense and a giant mess for sure.)

At any rate, the home was built by my family in the mid 70's. (that's why I know the history so well :wink:)

What should we be looking for when we demo the floor (and finally see the slab for the first time in 27 years)? I'm presuming there's a crack in the slab?

I entered tile heaven today....our local porcelanosa store... we picked out 1'x1' porcelain tiles... that company recommends installation with their own thinset/grout... I'm definitely not going to 2nd guess the company. I'm hoping that doesn't conflict with any possible solutions you tile folk suggest!

thanks so much for your input once again!

diy'er on LI 09-08-2009 11:11 AM


my husband looked at it this morning... he thinks one side of the crack IS higher than the other... sigh... I'll look at it again this evening when I return from work.

we decided that since we're laying the tiles ourselves, we'll demo the old floor well before we relay the tiles so we assess the slab situation in more detail... Don't know what we should be looking for though.

When I figure out how to post pics, I'll put 2 up... :-)

cocobolo 09-08-2009 11:47 AM

I thought of something else last night while I was trying to sleep.
Since the crack appears to be in a straight line, I wonder if you perhaps have a drain line, (or perhaps an electrical line in conduit, less likely) that has caused a weakness in the concrete?
To post a picture, scroll down when you are doing your post to "manage attachments"
Click on, then click "browse", select your photo from your computer,
click upload. Wait a few seconds it will load. Close the window, go back to submit reply & click.
Your picture should be there.
You will need to size it to 100kb or less first.
And one other thing about your tile laying exercise (check with a tile whiz on this) I think it is schuler-ditra (spelling??) that has the orange colored substrate for tiling. It separates the tiles from your concrete - or other sub floor, helping to avoid the problems you have.
I believe the romans used to set tile on a bed of sand which had the same effect. And many of their tile jobs are still intact!

diy'er on LI 09-08-2009 12:06 PM

2 Attachment(s)
thanks... I didn't realize the manage attachment option was down there. I was looking above the message area....

the top picture is of the tile in the bathroom. the bottom pic is of the bathroom door leading into the hallway (hall is top of pic)

cocobolo 09-08-2009 12:40 PM

Well, those cracks are remarkably straight.
One other small thing. I am going to lay some of those terra cotta tiles myself here, and of course they are quite thick.
When I mentioned the schuler-ditra (spelling again??) I should have noted that you may, or may not, have a problem with the overall thickness.
Your porcelain tiles may be only 1/4" or so thick. My terra cotta tiles are around 9/16" to 5/8", yours are likely the same.
So if you use the S.D. underlayment, your overall thickness may remain very similar.
Or, you could use regular cement board as well, which might help to alleviate the problem.
Not sure about that, better ask the experts.

diy'er on LI 09-08-2009 12:56 PM

I'm at work, so I don't have the sample tile in front of me, but you're right, it's not that thick. Right now, I'll guestimate it's 1/4". (wierdly, our wall tile is thicker than the floor tile... likely 5/8") The terra cotta is definitely thick. It's the handmade variety, so it is lumpy, bumpy, and likely 3/4". Due to the variability in the tiles, I wouldn't be surprised if the mortar beneath them is also thicker than it will be with the new tiles.

cocobolo 09-08-2009 01:07 PM

I am led to believe that the bulk of the Terra Cotta tile comes from the Guadalahara area of Mexico. And I believe it is all handmade, hence the variations and bumps etc.
Being a soft tile, it does not have the strength of porcelain, not by a long shot.
Now get back to work!

diy'er on LI 09-08-2009 01:45 PM


Originally Posted by cocobolo (Post 325282)
I am led to believe that the bulk of the Terra Cotta tile comes from the Guadalahara area of Mexico. And I believe it is all handmade, hence the variations and bumps etc.
Being a soft tile, it does not have the strength of porcelain, not by a long shot.
Now get back to work!

very true...

yeah, I really have to prep a pile of slides now... no more tile talk till evening :whistling2:

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