long crack over 4 floor tiles ?

[terry the tiler]

hi , i dont want to hear the answer to this one as i think i already no ! anyway hear goes ... ive a problem with a floor job i tiled around 6 mths ago, tiles are ceramic, floor was a hallway chipboard with no deflection and was not a floating floor . i stupidly over layed with 9mm marine ply as i didnt want to tile onto chip board ! addy was spf, ply had expantion gaps and primed sides and underneath. now the problem is 4 tiles have a perfect crack from one to the next at the centre of the door. ive got to go and investigate it further tomorow and just wondering wot the best plan of attack is ? the rest of the floor is perfect , and cracked tiles are not hollow when i tapped them ? would it be a option to remove cracked tiles and lay a bit of uncoupling membrain with spf then re fix tiles with a 2 part flexi ?

[Dave]

Might be a joint in the ply.. So a stress crack.. use a grinder to open the joint and fill with matching silicone to form a cold joint..

Not that i condone 9mm ply.

[jay]

9mm ply says it all sorry rip it out and use 6mm cement sheet all of it as the rest will fail later

[terry the tiler]

thanks dave ! i hope its something simple ish to put right .. iam NEVER using ply agaim m8 !! its just not worth it

[terry the tiler]

thanks jay ! iam gona have my fingers crossed it doesnt come to that m8 ! it just anoyes me that on the same floor he has his kitchen tiled directly onto the same chip board and its been stuck solid for over ten years