new marble tiles layed in the bathroom with underfloor heating - why is the grout cracking after 3 months?

Answer 1

If the tiles were laid on wooden floor, when they were laid and grouted the wooden floor will have expanded slightly with the water content in the adhesive/grout. Subsequently when the floor/adhesive/grout dried it would have shrunk slightly, even more so with the underfloor heating. It will continue expanding/contracting when heating is on or off. Flexible adhesive/grout should be used in those circumstances and the wooden floor screw fixed firmly beforehand.If tiling over floorboards, good quality ply sheeting should be laid and well fixed first. To a lesser extent this expanding/contracting will happen too on a solid floor, again, flexible adhesive/grout should be used, more expensive, but worth the extra cost. Also mix these as per instructions, too wet will weaken them.Were all these points considered when the tiles were laid?

Answer 2

I am assuming that the room is floorborded....if so they should firstly be screwed down in a grid pattern - not nailed.The correct sub floor must be used and firmly fixed, appropriate flexi-floor tile adhesive shold be used & also flexi - grout. Any minute movement within the floor will cause hairline fractures in the grout especially when the heat is turned on. My suspicion is that most of the correct materials have been used but that ordinary floor grout has been used, though I would have thought it would have cracked almost immediately rather that after 3 months, so the problem may be movement If this is the case it will always crack so you will need to rake out the faulty grout & re grout with flexi grout. & try to eliminate any movement that you can detect IF YOU DO RAKE OUT THE BAD GROUT TAKE EXTREME CARE NOT TO DAMAGE THE HEATING MAT UNDER THE TILES !!

Answer 3

If it's all of the grout, it's the grout itself.. chances are that the heat is causing expansion and contraction and that's making the grout fail.

If it's only in certain areas, it's likely flex in the floor or the underlayment..

Not good news either way.. If it's all of the grout, you should probably look into removing the old grout and re-grouting with epoxy additive..

Answer 4

I do not have an answer but my brother might. Look up the Grout Doctor on the internet. THere are locations all over the states and they have a toll free number that you can call. Sorry I didnt have it with me to leave.

Answer 5

It is not a problem with the radiant heat. I would say that the backer board or the sub floor was not fastened enough. You're probably getting Minor movement that causes the grout to crack.

Answer 6

1) Non flexible grout used??

2) Temperature too high?

3) Wrong type of sub-flooor?

Answer 7

all most certainly its the wrong grout ...grout used in these situations usual have a flexible base ..that is it allows expansion and contraction without cracking up

Answer 8

Because of the heat. Was the correct grout used?? I think not. You have been done mate....

Answer 9

im no specialist but i would say dodgy workmanship!!!