Here are some Do's and Don'ts of bathroom tiling
#1: First, always avoid high gloss finish on anything that is going to be near water. It becomes very slippery and dangerous.
#2: The size of the tile should complement your bathroom.
Ideally, for most bathrooms, you should opt for a 6" or 8" tile. Avoid larger sized tiles.
#3: If you are tiling an area that will be in a "wet" area such as a shower wall, then you will want to use a gypsum product which is moisture resistant rather than plywood but this is not required for the floor (unless you are doing a pool area).
