If you are going to re-do the bathroom floor - this means taking up your tile, sheet vinyl, or ceramic tile and underlayments you should make sure there are no signs of water damage to the subflooring and check to see if it is solid throughout. When laying down a new floor the main question is always can I lay tile over the existing floor or do I have to pick up the old one first?

If the floor is level and sound you can usually just tile right over it with plastic or vinyl flooring, but keep in mind how mush room you have for the bathroom door, door frame and wall molding (if any) you may have to open or close the door from time to time!

If the underlayment is solid but not quit level you can use leveling embossers (like mortar) to fill-in low spots to make a level surface, otherwise place a new underlayment over it, if you can. I have seen home owners doctor it up with thin plain wood strips dont do it! All materials must be water and moisture resistant as possible. Always use at least a 3 ft level to insure surface is not slanted in any way.

For a typical ground level home like a ranch with no basement, floor foundations are 'framed', meaning the floor sits on joists with 2-by's (stills) running perpendicular to the joists along the foundation. 'Girders', (metal rods) at or near the center of the joists help in support. Above the framing lays the subfloor, typically a 3/4" tongue and groove particle board, plywood or similar material. Above that there is a1/4" plywood or cement board (moisture resistant) thats called the underlayment and may also have a sheet of roofing felt or similar material for added cushioning. Take extra caution when laying underlayment over the subflooring because the floor may crack if the seems match up so it's best to stagger the seams.

Ceramic Tiles: Because this type of tiling has become popular in kitchens, bathrooms, halls and even living rooms for its durability and style, I want to devote this section on the subject.

Installing ceramic tiles in the bathroom will alter the height of fixtures like toilets, vanity sinks and cabinets as well as the door and adjoining room it is best to remove everything and start from scratch. This means removing the old underlayment as well. You have to create a level surface or the tiles will crack or break. Most ceramic floor tile is thick so you will have up to added to the old floor assuming you had plastic tile or vinyl to begin with. You will be offsetting the height of the old fixtures and the door so a bit of trimming may be necessary (If you are replacing fixtures-no problem).

For best results follow these steps:
* Using a 3ft level check if the floor even throughout
* Lay out a row of tiles, with spacers (cross shaped inserts for grout lines) along the length and width of the room to gauge how many tiles you are using. This is also to see how many tile cuts you will have to make near walls.
* Lay down cement board, cut to fit area and use a small layer of mortar to attach board to subflooring. Use screws every 6 to 8 inches along the edges of board to secure in place. Use mesh tape over the seams and cover with a thin layer of mortar.
* Using a trowel apply mortar about every 3 1/2 at a time and use smooth even strokes.
* Set the full ceramic tiles at a point furthest from doorway and press down firmly, tapping it with a rubber mallet so it spreads evenly. Have the cut tiles ready so as you move away from the wall place and set as you go.
* insert cross shaped spacers on end between each tile to insure rows are even. At corners lay spacers flat and butt tiles at the angles (dont worry, it will be same with). You can also stand the spacers upright against walls.
* When you get to the closet flange (toilet hole in floor) you will need a tile nipper or tile saw to cut a partial circle. Do this for all sides and lay down as before.
* When all the tiles are down you must wait a least one day for it to set properly this is an important step before you put down the grout. When ready, mix tile grout to cover about of the room at a time, this will give you time to do to right. Take out the cross spacers and apply grout with a grout float, then holding float at an angle squeeze off excess grout. Do this with step with the rest of the room.
* The last step is to dampen a clean sponge with water and wipe off the access grout, rinsing the sponge often.