R
Rich
Thats alright, lets hope that you get paid to sort it out when it cracks and lifts again 
Chipboard is not stable enough to be tiled onto, it is made up of loads of little bits (off cuts). The slightest difference in moisture or humidity the chipboard swells and contracts, this will break the bond between the tile and the floor. If the chipboard is screwed down properly and there is no bounce in it, you can over board with a cement board but if not I would rip it out and replace with min 18mmboill and water proof ply then over board with a 6mm cement board. Have a read through the link below.
[h=3]Plywood floors...[/h]
Chipboard is not stable enough to be tiled onto, it is made up of loads of little bits (off cuts). The slightest difference in moisture or humidity the chipboard swells and contracts, this will break the bond between the tile and the floor. If the chipboard is screwed down properly and there is no bounce in it, you can over board with a cement board but if not I would rip it out and replace with min 18mmboill and water proof ply then over board with a 6mm cement board. Have a read through the link below.
[h=3]Plywood floors...[/h]
