There's one thing to know about concrete either it's already cracked, or it's going to crack. Cracking concrete tends to crack your tiles since they're attached to one another. Whether you are planning on using a concrete or plywood base, you may want to consider using the Schluter DITRA Underlayment System. This product acts as a good substrate to avoid this issue. It's lightweight, thin, waterproof, and comes in several varieties. How it works Column-like mortar structures are formed in the cutback cavities of the matting. Loads are transferred from the tile covering through these column-like mortar structures to the substrate. Since DITRA is virtually incompressible within the tile assembly, the advantages of uncoupling are achieved without sacrificing point load distribution capabilities. The ability of DITRA installations to support and distribute heavy loads while preserving the integrity of the tiled surface has been verified through laboratory and field testing, including applications exposed to vehicular traffic. This hidden gem is for builders everywhere to help add life to tile floors. Dive into this video for some tricks to make your floors more efficient and your job much easier! More info on DITRA at the official website here For some general pricing, here's Ditra XL on Amazon.