Grout joints cracking

[Mattash99]

Evening

1st time poster, so here goes

I have a 2 part floor, half on the original screed which has an electric matting system(supplied and fitted by the electrician) and half on the new screed which has the water system in the screed, the floor was laid about a year ago. The new screeded area is fine, no cracks in the grout, but the original area on the electric matting the grout has cracked, this isn't the 1st time, happened about 6 months ago, which I put down to the UHF being on about 100 degrees, so removed all the grout and regrouted, told the client to leave it 28 days, start it low and increase it by 5 degrees, now they're saying they haven't turned it back on and it's just started to crack again, the tiles are 600sq porcelain which have been backed, used webber SPF, not really been built up, the tiles are still solid, it has ditra down and I used Arduit FL grout and am pulling what hair I have left, out!!! Anyone got any ideas, would be massively appreciated

cheers Matt

 

[cam_low]

It's the new area floorboards?

 

[Ajax123]

It's the new area floorboards?

No it's the original screed...?? Although my thought was flexing as well.... What is the original screed floor makeup?

 

[cam_low]

Half asleep Alan lol draining day today.

 

[White Room]

Do you have any thermal boards under the ufh on the original floor which has grout cracking...

 

[Mattash99]

Not sure of the original screed make up, but it was solid. No thermal boards, straight on the original and then latexed over.

 

[Mattash99]

Do you have any thermal boards under the ufh on the original floor which has grout cracking...

No thermal boards, UHF latexed a couple of times over, then the ditra and then the tiles

 

[cam_low]

A recipe for a good solid floor. No wonder you are scratching your head.

Is there any expansion gap between the two screeds? Should there be?

 

[Mattash99]

No expansion joint, but can't see as that's the problem, as the tiles are still solid. Is there a way to see if the UFH has been switched on, as my betting is there's too much heat emanating from the mat, but then I think the tiles would sweat and then blow, so I'm still fairly confused

 

[Ian]

Has the wet UFH been turned on? Is there any chance the expansion from that side of the floor has caused movement on the side with the electric UFH?