SUBFLOOR FOR CERAMIC TILE FLOOR
#1

I WANT TO INSTALL CERAMIC TILE IN MY KITCHEN, CAN I INSTALL A SUBFLOOR OF 1/2" PLYWOOD AND LAY THE TILE OVER IT.
#3

I would use 1/2" cement board. Its designed as a underlayment for tile. Having a rigid subfloor is the key to a good tile job. Deflection should be almost nonexistent and the recommendations for the thickness of the total subfloor is 1 1/4". Follow the mfgs. recommendations in putting down cement board.
#5

Cement board is actually cement. Common brand names (in the U.S. anyway) are Durock, Wonderboard, and Hardibacker (I'm not sure whether Hardibacker is actually cement). It's usually sold in 1/2" and 1/4" thicknesses, and in 3'x5' or 4'x8' sheets. Cement board has a rough side (for mortar) and a smooth side (for mastic). On floors, it is usually set in mortar and screwed down. On walls, it is usually screwed to the studs, often with w vapor barrier underneath (use the 1/2" on walls in place of drywall).