Help with cracked grout on new tiled floor

[GAZ5518]

Unfortunately I think it’s all been covered in the various feedback comments
once upon a time Tiling straight on ply was acceptable ... but alas no more .
Anti-fracture matting should have been installed.
If the Tiles are stuck well .. you could try and rake out / regrout using a flexi additive.. but no guarantees...
Wish you well with the remedial.

 

[JA Tiling]

Unfortunately I think it’s all been covered in the various feedback comments
once upon a time Tiling straight on ply was acceptable ... but alas no more .
Anti-fracture matting should have been installed.
If the Tiles are stuck well .. you could try and rake out / regrout using a flexi additive.. but no guarantees...
Wish you well with the remedial.

Thanks for the reply I raked out the grout and regrouted with flexcolour a week ago and the customer contacted me yesterday to let me know everything was still OK so fingers crossed 🤞

 

[MonsoonJC]

Don’t know why people keep tiling onto plywood it really is not a good backing for tiles wood expands and contracts a lot more than tiles ever will,

I completely agree...

 

[Huddersfield Tiling]

Hi everyone, I tiled a kitchen and living room floor last week and the grout has started to crack in both areas.

The customer laid 6mm plywood on top of chipboard subfloor and was screwed down. The tiles were a ceramic floor tile 45cm x 45cm with 8mm notched trowel Mapei ProFlex adhesive was used and Silver grey Larsen flexible grout was used the next day after tiles were laid.

The customer started to move couches appliances etc into the rooms around 6 hours after the floor was grouted and noticed the grout was cracked after moving the stuff back into the rooms.

It seems to be the areas were the grout is cracked is where the most foot traffic is, both rooms were around 30sqm total but grout is only cracked on around 8 sqmin both rooms combined. I haven't been back to the job yet but I am unsure what to do and I'm looking for some advice the tiles were solid when I was grouting them and everything seemed fined when I left the job.

Any advice would be much appreciated thanks

The VERY simple rule is this:
If the grout has cracked, then the bond between the tile and substrate (what the tile was bonded onto) has failed.
There is never any other explanation other than movement due to moisture or instability. If this is one area only, it only shows that it's a weak area in a poor installation, or a point of moisture. The sub-floor won't have been prepared properly throughout, or there was a water spillage. Therefore the tiling has failed, and it needs to be completely ripped-up, properly prepared and replaced with new tiles. Sorry.