I have a finished basement (with concrete subfloor) that has half the floor tiled with ceramic tile and the rest with carpet. I have removed the carpet (due to unruly pets) and decided to replace with matching tile. This would be my first time working with tile. My issue is that I would need approx. 3/8" of thin set mortar/mud to bring the new tile level with the existing tile. Should I put the mud on extra thick to make the floor level or should I use some other material as a spacer. I appreciate any advice, thanks in advance.