I have 12 cracked kitchen floor tile in 2 areas of the floor, 6 in each. The cracks are basically running in a straight line thru the tile in each section. I'm assuming the cement board joints have lifted or moved somehow beneath those tile, guessing because I haven't removed the tile yet.

The flooring beneath the tile is a plywood subfloor which seems to be tightly attached to the floor joist beneath. On top of the subfloor is 1/2 inch cement board. Can you tell me the best method in re-attaching the cement board or is there something else I should consider? I am fairly handy but never worked with tile before.

I have 13 tile that match. I cannot find anymore locally so I need to be careful and do it properly, thus your advice is greatly appreciated. Thank you