Dave

hi rossy.....

If a couple of tiles have cracked then this could be a sign of trouble ....

If the qaurry's are tightly butted together then expansion problems could be at fault..

Check to see if the tiles are debonded by tapping on them..if they have a hollow sound


when you tap them then they will be loose...... then it will be advisable to remove and

make good the floor. If they are in a solid condition then you will be able to tile over them.......dave..