Next find out if any kind of building permit is required. Again, this varies from city to city and calling your local city or town offices should get you your answers.
If a permit is required you may want to secure it yourself or ask the tile installation company who will be doing the work for you if they can obtain a building permit for you.
No Sound Proof Underlay = Big Problems For You In The Future
Before beginning tile installation, the floor surface should be thoroughly cleaned and properly prepared. A layer of sound proofing must be installed first.
This will create a base for the tile. Then you will need a layer of water proofing. This will protect the subfloor from any water that spills onto the floor from seeping through the tiles.
If this occurs the result can be serious sub strait damage. Water spills are a likely occurence in a bathroom. Water overflow from the shower or tub is most often the culprit.