Uneven wall/tiling

As a new DIY tiler, I have found this forum extremely helpful with practical advice from pros.

Here is my problem:

I am about to start tiling walls of my house powder room. The walls have existing sheet rock finish. I have removed the old wall paper. As I checked the leveling of the walls, I noticed that at the center of the wall sheet rock is 1/4" raised as compared to either side of the wall. The tiling area is approx. 80" long and 48" high. The ceramic tiles that I am planning to use are 8"X12".

Quetions:

* Is wall priming (by latex) needed before tiling?
* Is 1/4" gap too much to "fix" using 1/2" trowel towards the ends and 1/4" at the center?
* Am I better off fixing the wall by plastering to level (I would rather not)
* Any other ideas?


Considering that this is powder room, and my first job, I would gratefuly appreciate your help.

After you finish tiling, the 1/4" rise will be COMPLETELY unnoticeable. Just tile the wall normally and do not attempt to straighten it with the thinset mortar. If you try it, you could make the finished tile uneven. I assume you NEVER noticed the "bulge" since you moved in, and you won't after tiling either.

I doubt you could successfully plumb a wall by varying the mortar thickness. 12" tile are large for a wall, and are more difficult to install, but 1/4" is not much, and you should be ok. Use a latex modified thinset, or a type 1 mastic, which is what I prefer on walls. Get some recomendations from the tile store, or the tile forum johnbridge.com , about surface prep.

That hump is fairly normal, they add the tape and mud mix to level the horizontal seam. Course, it could be for other reasons, but that is the most common. IF the paint is well-adhered, the moisture from the thinset or mastic's solvents should leave it alone. But, that is always the biggest possibilty, it breaks the bond with the paper on the drywall and then you have loose tile.

On a new installation that is going to be tiled, you don't need the normal tape, or any mud, or primer...the tile and thinset will bridge those seams. To make it stronger, you would use the special, alkalai resistant mesh tape designed for use on cement board on the seams.

Big tile work much easier if the surface is flat. To help keep all of the edges in plane, there are severl tile laying systems you might want to consider: Tuscan Tile Leveling System, and LASH. Each of these uses a break-away widget that holds the edges perfectly in alignment. Once the thinset cures, you break away the above tile portion and then grout. The Tuscan system requires you to buy a special tool to install the widget (sort of like a tie-wrap gun). LASH uses a reuseable wedge and no tools.