The problem is that the wall is uneven.
Tiling onto uneven walls.
Self levelling compound for an uneven floor.
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.
Then flush and fill the areas with cement.
Things you will need measuring tape tile wet saw leveling spacers and wedges trowel thinset mortar rubber mallet grout grout float grout sponge.
Plastering the walls is the best way to ensure that the walls are nice and even.
Use a flat scrap of wood to even and smoothen out the surface and let this dry for a few hours or overnight.
Level those uneven walls.
You want the tile adhesive to have something to grab onto.
Once the cement is dry apply the bonding agent that should give the surface a rough texture.
For an uneven concrete floor a floor leveller will solve all your problems.
If you put a 48 straight edge up against the most sunken areas there s a gap of almost a 1 2.
The mortar is spread.
Sand with a medium grit sandpaper to create a uniform surface that s not too smooth.
How to prepare an uneven wall or floor for tiling plastering.
Thoroughly vacuum the area and give the wall a once over with a damp sponge or cleaning cloth.