If you re tiling over an uneven section of wall the corners of the tiles may stick out slightly from the rest of the tiles.
Tiling very uneven walls.
If you put a 48 straight edge up against the most sunken areas there s a gap of almost a 1 2.
The problem is that the wall is uneven.
One very big problem that not many people realise if the wall isn t really flat a brick joint pattern will show off every out of plane point in the wall by virtue of sticking out a half tile from the tiles above and below it.
The mortar is spread.
There is also a spot near the window trim where the wall appears to be built up too much enough so that the tile could end up proud of the trim which i m pretty sure won t look so hot.
If you don t think you can trowel a coat of mortar to get it even withing about 1 4 the tiles will further even it out when set i would investigate a possibility of mounting a cement board onto the bricks instead.
This is known as lippage and it can diminish the most professional of.
The board will create a perfect backing that will make setting tiles on thinset look like a walk in a park.
Being that she s not going to be there very long that might be fine.
One of the best ways to ensure the surface of a wall is even is to plaster it.