Grout cracking

28 Sep 2004
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United Kingdom
I recently had some ceramic floor tiles laid (by a pro) directly onto bathroom floorboards. The floorboards are nice and thick and felt solid and the tiler used the flex stuff. (told me he used double recommended amount to made sure they stuck!)

Anyways, after a few days use I have noticed hairline cracks appearing in the grout and in the centre of the room where most traffic is a line of tiles push down when pressure applied ever so slighltly (say 1mm max)

I'm hoping the tiles will stay firm and the cracks will get no worse. Can you get a flexible grout or alternatively is it worth squeezing some clear sealent into the cracks which may offer a bit of movement with the tiles.

I appreciate that may sound slighlt cowboy-ish but unless the situation really gets a lot worse the option to rip up the tiles and start again really is a no-go. Should also note that due to having friends over we only left it about 24 hours before people started walking on the tiles, would that have been sufficient time for the grout to dry out and harden properly?
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If he used readymixed flexible adhesive it needs a minimum of 24hrs to go off, more if he put a lot down. Did he screw the existing boards down or just leave them nailed?

If it was powdered adhesive then 24hrs for normal, 3-4 hrs for rapidset.

He should have used a flexible grout which would need 24hrs to set once the adhesive was dry.

If you have 1mm of movement in the tiles then no grout will stay solid, it would have been best to overlay the boards with ply, screwed at 200mm cts

would agree with what Jason said but a while back I laid a couple of tiles on some readymixed flexible adhesive, because i ran out of fastflex, I had to lay it on thicker than the 6mm recommended due to a dip in the floor, three days later the tiles were still moving and when I lifted them the adhesive was still not set. I ended up buying some fastflex and relaying them.Also as most flexible adhesives dry to a very hard rubber type finish if you lay it on too thick there may be quite a bit of movement caused by the inherent flex in the adhesive.always use flexible grout with flexible adhesives
Adding more glue of any kind to anything is not going to make it stick better in fact quite the opposite.
I would get him back to sort it.
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Thanks for the replies. It was a readymix flexible adhesive he used.

From what you say it sounds like (hopefully) some flexible grout left to dry properly will resolve any problems. I'll give it a few more days to see if it deteriorates any further then call him back to sort it.

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