Flooring project.

I am currently installing a shower and along with it I am going to tile the bathroom, entry foyer, and kitchen floors alike; they do all run together. The bath and foyer are now standard 3/4" hardwood floor and the kitchen is sheet lanolium. My question is can I go over the top of all of it or do I have to take everything down to the sub floor? If you know any pros and cons of the situation I would appreciate your advice. Thank you!