Hey,

I'm about to start the tiling process and have some prep to do but I have one question.

I live in a condo. The cement that was under the tub is fresh, clean and looks even. I am not removing the old tile from the rest of the bathroom as I'd like to bring up the height a little to hit flush with the room outside's floor.

Do I need to use a scratch coast to even things out? I've been told yes but my surfing puts fear into me. I won't be using it to tile but just to level the two layers between tile and cement.

So for now, I'm sanding everything with a belt sander to begin so the scratch coat holds. I'll trowel the scratch coat and once dried, I start tiling on top of the scratch coast using a modified thin set mortar, correct?

Your post leaves some room for interpretation. Scratch coat is a process of skimming wire mesh with thinset. I believe what you are referring to is skim coating your tile. I would say that skimming the floor is a waste of energy. Just rough up the tile, then wash them and wash them a second time with clean water to remove all dust. Then set directly on that with the best quality modified thinset you can afford.

If your existing tile is uneven your best bet is to grind off any high spots. and fill in holes with thinset, but you don't really need to skim the whole floor.

for the part under the tub that is lower than the tile you can use self leveling compound or thinset. an easy way of getting things even is to set a strip of wood the thickness of the tiles against the back wall and then slide a screed on that and the tiles at the same time.

My question is, what's under all that? Is your old tile sound - no cracks in the tile or the grout, no hollow tiles, and no loose tiles? Might want to have a good look before you spend a bunch of money - a little time now investigating is inexpensive.

Thanks guys, very much appreciated.

Underneath everything is solid concrete - I can't be sure of holes but there are no loose tiles, there is good grout, etc. It all looks solid.

I went at it last night with a belt sander. I had actually brought the level of the cement up already with an unmodified thinset so the difference in level between the old tile and the exposed thinset/cement is pretty minimal (2mm maybe?) Should I get that wood? I've avoided any and all wood in the bathroom because I thought it was against code. I've been using 2x4 metal studs behind the walls.

So if the tile is sanded and the modified thinset has something to hold, the level is pretty close - then I should just tile on top?

I thought the scratch coat was to level and give the thinset something to adhere to. Don't know anything about the wire mesh.

oh and btw - my plan is for high quality to use the dynaflex 600 (www.dyna.ca)

What do you think?

The wood piece is just to get the right height for screeding and comes back out after. a good modified thinset will bond directly to tile. A 2mm difference is actually quite a bit and should be corrected prior to setting. i have no experience with Dynaflex, but if the stuff is less than around $40/bag it's probably not good enough for tile over tile.