Porcelain large format floor failing - Tile Advice

[Mlew]

A year ago we completely refurbished our kitchen including a new porcelain tiled floor installed by the builder.

I think he put ply on top on floor boards, and then put the tiles on top 600x600 on 30sqm. I think the ply was prepped.

The grout is cracking in many places now and the tiles are moving in those places but not cracked. There doesn't appear to be a lot of bounce in the floor but clearly something is wrong. Flexible grout was used I don't know if they back buttered the tiles I suspect not.

We have a large island 3mx1.2m on top of the floor. The builder said it was the grout and they could use silicone to seal it hence why I now need a tiling professional because that solution does not sound right.

Any advice on what needs to be done please?

 

[Steve6690]

The grout is cracking because the tiles are moving and the tiles are moving because the prep hasn't been done properly, or they haven't been fixed properly and have debonded.. I doubt you'll find the cause without lifting tiles and seeing how the ply has been fixed or what the floor is like underneath it. I certainly wouldn't let the builder fix it until the fault has been identified and rectified. For one thing, although I'm not a pro tiler, I would always use a decoupling membrane such as Ditra on a ply floor, but I really wouldn't use ply anyway tbh. Hardie backer would be my preference. Hopefully some pro's will chip in on this too.

 

[Perfect Tiling]

The tiles are all loose....because they were put down by a builder and not a tiler I'm afraid. The ply he put down is probably 5 - 6mm.....it has to be 15mm and primed on the bottom and edges. I will never tile onto ply as it often fails its better to put down something like a 6mm hardibacker board which is glued and screwed with all joints taped and filled. For tiles that size its best to use a large format type adhesive which is combed onto the floor and back buttered onto the tiles to achieve a full bed of contact. The grout lines look small to me....they have to be a minimum of 3mm with expansion allowed for at all edges and change of floors. DO NOT allow the builder to just put silicon in the joint gaps to hide his errors. Tap the odd tile and see if it sounds hollow...I bet my life they will...meaning they are loose and the whole floor will need to be redone...properly!!