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