Designing Kitchens and Bathrooms - old wall preparation for ceramic tile install

I have guys preparing bathroom to install tiles. I removed the old plastic (?) tile and the glue (adhesive) remains on the wall half way and the upper half of the wall has paint on it. They were putting some kind of smelly "caulk" or silicone on the parts of the wall where old glue is without removing the old tile adhesive. Also they told me that there is no need to roughen the upper wall surface where the paint is. Are they doing it correctly or am I in for a tile failure in the near future? How should it be done correctly? I'm talking about old bathroom walls that have some woodboard with old plastic tile adhesive on it (lower half) and paint with wallboard (sheetrock?) on the upper part of the wall. Part slab part vinyl tile on the floor. Please help before tomorrow if possible. Thanks very much.

Sounds like your "guys" might be a bit flakey...

1. What is your substrate? If it's plasterboard - it's wrong. The best substrate for a tile surface is a masonry based board (ie Wonderboard)($10.00 per 3 x 5 X 1/2inch sheet). With a good vapor barrier (plastic sheeting/tar paper) behind it, you get a virtually waterproof backing for your tile (By the way - a tile wall is NOT waterproof. The backing will eventually get moisture seepage - and plain ole plasterboard will end up disintegrating one day.

2. Your surface should be free of old paint/glue/crud - for your new thinset to adhere properly to. Again - a tile surface is NOT WATERPROOF... merely slows water down on it's way into the inner surfaces...

Not trying to push a pro on you (I'm not one either)... but hate to see you spend money/time on that won't last.....

As your tile sounds like it's going on tomorrow..... Good luck - hope you make a proper decision.

Thanks for the reply. I'll tell them tomorrow to do it properly. They said nah it will be ok, but I will not go with their installation. Thanks for the vapor barrier suggestion, they wrere not going to do it as well. Now about this thing that worries me: THEY ARE PUTTING CAULK/SILICON (?) over the old glue/adhesive that was adhesing the plastic tile to the wall. I told them (being not a professional) to remove the glue, but they said they put this stuff on (caulk? silicone?) and will be ok. But how can silicone or caulk be put on an old adhesive glue and then tiles put over it? Also how about they are saying they will put tile over the upper wall area where there is old paint over plaster? They said tiles will stick there anyway, no need to rough/sand it. I was in doubt that's why I posted here.

You can get tile to stick to bubble gum, if you want it to.... and it will last - long enough for the contractor to get cleaned up and off the job site....