Porcelain tiles cracked

[Cheryl]

Hi there,
I really hope someone can help. I had new porcelain tiles fitted over electric underfloor heating a few months ago and, wherever a tile has been cut (like a corner), they now have a hairline crack. These tiles are over Vysal underfloor heating. Is the problem with the heating or the tile, or something else?
Many thanks for any help.
Cheryl

 

[Stewart]

Does the floor have room for expansion around the perimeter. Sounds like the tiles have been grouted to the wall or cut tight to it. A couple of pics would be handy and some more info on how the floor was tiled would be helpful in our diagnosis.....

 

[Cheryl]

Hi
Thanks for your quick reply.
The tiles had a gap of about 1/2 inch before the wall (we placed skirting on top) so I don't think its expansion. Half of the floor was suspended (so it had ply before tiling) and the rest was concrete but it has happened on both.
Cheryl

 

[Stewart]

How thick was the ply, did tiler slc over heat mat before tiling,is there an expansion joint between the ply floor and the concrete.....?

 

[nybor62]

pics please would help

 

[DHTiling]

Hi Cheryl and welcome....

Can you please upload some pics, so we can see what you can.., also if possible can you remove one of the cracked tiles so we can see what has happened underneath.?

 

[Cheryl]

Hi
If slc means levelling compound, this was only done in certain areas, not overall. Re the expansion between the ply and concrete, there is not currently a problem where these meet at all.

 

[Cheryl]

Hi
At the moment, the crack is so hairline, its not easy to see but I kow it will look worse in time.

 

[Cheryl]

Ok will try to take photo but the line is very thin, its just happened.
will come back to you.

 

[Spud]

cheryl did you get the carpenter to leave a 2mm joint when the skirtings were placed ontop of the tiles? this is very important as skirting that are butted down on to the tiles can add to the stress the floor is under when its heated also how do you use your under tile heating do you leave it at one temperature or often change the temperature settings ?

 

[Cheryl]

Hi
I've tried taking a photo but because its just happened and the hairline crack is still so clean, its impossible to see on the photo. If it was the skirting causing the problem, I would have thought it would have happened in other places but it has only happened where the tile has been cut to fit a protruding corner (6 places so far), the crack is a straight line from the V of the corner, - hope I've explained it ok. I can't take up a tile because none are loose.
Re the underfloor heating - it is thermostatically controlled but I would not have thought it gets hot enough to crack a tile, especially a porcelain one - its only warm underfoot not hot. These tiles have been laid since July and it has only started to happen. Also, we waited much longer than the recommended 2 weeks after the tiles were laid before the heating as even tested.

 

[Ian]

Hi Cheryl, so all the cracked tiles would be around door frames etc, is that right?

 

[Cheryl]

Hi
My kitchen is not a regular shape and the tiled floor flows into the conservatory so there are a few corners to go around and it has only happend at these corners, nothing at the door frames (yet).

 

[DHTiling]

IMO Cheryl, it is stress related.... L-shape cuts are the weak point hence cracking at this section.... if it is on the corners where the floor flows into conservatory, then an expansion/stress relief joint should have been installed at this point..

How long is the longest run of tiles ..?

 

[Stewart]

It does sound like they don't have any expansion on their perimeter. L cuts are generally more prone to cracking if they don't have enough expansion around what they've been cut around! also how do the tiles sound when you tap them with your knuckle.... do they sound hollow at all?

 

[Cheryl]

Hi
The longest run is just over 11x600mm tiles so just over 6.6m long (this length of run is in three directions) - about 58sqm in total.

 

[Stewart]

Could you please post some pics showing the tiled room, we don't really need to see the cracks....

 

[DHTiling]

6.6 lnr mtrs is just about ok... i still think it is stress related.. you have the option to leave it to see if it gets worse and then rectify or remove and see what is causing it..

 

[Cheryl]

I'm so sorry, I'm really not good at this and can't seem to attach the photos I have taken.
I was wondering if the L shaped cut had created a weakness in the tile that has taken time to become evident. I have tried knocking the tiles and there is no hollow sound at all and there is certainly no flex.

 

[DHTiling]

you upload pics using the attachments feature is post rely advanced.. http://www.tilersforums.com/newattachment.php?do=assetmanager&values

 

[Boswellnick]

Might be far fetched here, I have been tiling in Sweden for a long time and out there they recommend a minimum of 6 weeks before turning on floor heating..

 

[Cheryl]

Hello again,
By the way, thank you so much to everyone who is trying to help with this. At first I thought it might have something to do with the underfloor heating but the heating mats are about 30cms from the perimeter of the room and it is there (on the L cuts) that the cracks are. There are no cracks anywhere else (yet). Could the tiles be at fault or could the tiler have created weaknesses when cutting? I really don't think it is stress related (because not tiled up to edges) and absolutely no flex in floor. Where tiles are cracked, they have not lifted, it is literally a fine line from each right angle of the L cut.

 

[DHTiling]

The L-cut is the weak point and expansion stress in the floor may cause them to break at this point... your option is to replace and hope that it was just the initial warm up that has done this and might not happen again.. but without seeing the floor at face value then we can only summise..

 

[Stef]

Hi,
Is this a new build house? Is it a new conservatory? How old is the concrete floor & how thick is the ply overlay?

 

[John Benton]

If it is only on the L-shaped tiles with the cut-out, are the location of these tiles at a corner where the skirting board is, or are they at the corner of the end of a run of kitchen base units? Are the kitchen units fitted on top of the tiles or are the tiles fitted around the end panels? I'm asking because if the tiles are scribed around decor end panels it could be movement here that could be causing contact with the tiles, and in turn causing them to crack other than movement in the floor. Locations of cut tiles would help.

 

[Cheryl]

The location of the cracked tiles is only on corners where the skirting board is. The whole floor was tiled before the new kitchen was installed and nothing is cracked under or around the units. The house is not new (1930's) and the conservatory is 8 years old so no movement there, I don't think.