I've put down two bathroom floors and a sunroom floor, and did a good deal of research before I did them. From everything that I understand, tile needs to go on a flat, stable surface. I may cost you a bit more to rip up the old tile, put down some plywood, and then tile but in the long run I think it is worth it. The old tile is probably pretty stable but if it is not perfectly flat, you risk your new tile cracking.

I look forward to hearing what other say.

Suzanne

I'm sorry, but I have to disagree. Good chance that if that floor is original to the house, it's a mudset floor (IOW, it's got a wire reinforced mortar bed under it about 1- 1 1/2" thick). This means that providing the old tile is in good condition (no cracks or hollow spots), you've got one of the strongest, most stable subfloors you could ever set tile over. You want to hit the face of the old tile with a sander and coarse sandpaper to get rid of any contaminants and to scuff up the face and give the thinset something more to "grab" at, and then use an unmodified thinset mixed full strength with a liquid latex additive, such as Laticrete's 317 thinset mixed with their 333 additive. So long as you have no elevation issues with radiators, doors (that can't be undercut), or the toilet flange, you should be good to go.

Bill - followup question. I'm also in a 1929 apartment in NYC, and my current bathroom floor was put on top of the original floor. It is definitely not a straight flat floor now, since there are dips and drops in areas, leading to the toilet and sink not sitting straight. So, if I replace the floor, can they remove the top layer and still leave the original floor, or would it be better to remove them both?

It depends what condition the original floor is in once the top layer is removed. If it's still in good condition, then yes, they can.

Bill - I suspect you are right about the floor. My walls (apt is also in NYC) have mud bricks in them, apparently, and one contractor told me that, in those days, the mud? was poured between the floor joists(?) and could now have settled so that the top of the poured mud is below the level of the joists.

Do cracks preclude laying the new floor over the existing one? Also, the floor is slanted slightly. Even in the areas of the cracks the floor is very smooth.

Another important thing you mentioned was the door. I am keeping the tub as it is a large, cast-iron j-tub, but I am not sure that the door would look right if it were undercut, and I'm not sure I want to do that anyway as I also like my original doors.

Thanks for providing the grout information. My tile company wants to give me TEC unsanded grout with latex added but maybe I will need a different or an additional product.

(I hope nothing happens to my downstairs neighbor's apartment during demolition. Worried.)

Do cracks preclude laying the new floor over the existing one? Also, the floor is slanted slightly. Even in the areas of the cracks the floor is very smooth.

Chop it out and start fresh.

Our house was built in the 30's. The bathroom was last renovated in 1980, with new tile over the original floor. I would imagine it was level, as the floor is solid, no cracking, chipping, dipping or anything else. If it weren't so ugly, we wouldn't tear it out next month when we reno the room. But we are going to! :-)

I just removed a stained rug from the bathroom floor and found tile, some of which is cracked and some missing around the toilet. Can I still put new tile over this old tile?

bikrchc...just wondering...is the original floor tile in bad shape and that is why you are replacing?