Hairline cracks on a new floor

[hps1]

So I've returned to a job today to put some tiled skirts on and I see hairline cracks on the floor! Only in grout lines. 30m2 floor 600x600 porcelain tiles double buttered with tile master rapid setaflex onto dura Matt and using grout 3000. Floor was Alfa hemi hydrate that's been moisture tested correctly and underfloor heating commissioned and turned off before I started. I'm pretty damn sure that the customer has put heating on too much too soon even after me warning him.... so my question is what else could cause this??

 

[White Room]

What was the dura matt stuck down with...

 

[One Day]

Sounds like they've put the heating up before the grout had bonded fully to the porcelain. Hence the cracks in the grout. Shrinkage.

 

[NZ_Tiler]

Sorry to hear ya problem.

Won't help on this project but for the future jobs, there are these german things "plombe".

Not sure if they're used in the UK.

Basically glue it under a tile and it will record the highest temperature the floor reaches. If the worst happens you at least have evidence the heating has been cranked up to hot.

Heizestrichplomben, 4 Stück, Art.-Nr. 40438 - Fliesenlegerwerkzeug | Fliesenschneider | Diamantwerkzeuge und Nivelliersysteme - Karl Dahm - http://www.karldahm.com/Heizestrichplombe.htm

 

[hps1]

What was the dura matt stuck down with...

Anhyfix.

 

[hps1]

Also none of the tiles are loose

 

[hmtiling]

I've had this before. The customer swore he followed advice regarding heating. The tiles I used were trav and no cracks in them. I don't use grout 3000 anymore.

 

[hps1]

I've had this before. The customer swore he followed advice regarding heating. The tiles I used were trav and no cracks in them. I don't use grout 3000 anymore.

Cheers Harry, Kris have me your number the other day I'll give you a call in near future. So do you think I would have had same problem if I used Mapei ultra colour? To be fair I've used 3000 on loads of heated floors and not had this problem. My issue is how to deal with it with the customer as I feel it's not my fault. I advised him the longer he leaves it the better, but minimum 2 weeks and then turn up degree a day but you know what it's like, as soon as you walk away and the decorator or kitchen fitter needs heat on bla bla bla

 

[One Day]

Some thermostats have engineer modes which will record the first few days usage. I know warmup have that feature although you may need to contact them for details. Might be worth looking into? Even if a different thermostat?

 

[Valentin]

Or you might grouted too early after tiling. If the grout cured before the adhesive did, than will appear cracks in grout as a result

 

[Kevbos]

If grout cracking .tiles still stuck .then grout is the problem. If cracks in grout are around every tile .then too much water in grout ,if cracks only on certain areas then subfloor has shrunk .grout gave way .this suggests heating turned on too early .every floor i do with underfloor heating .i tell client 4 weeks before heating goes on .then lowest setting .it must stay at that regardless for 2 weeks .then turn up a couple of degrees weekly..as we can never know what they actually do .