Attach a straight board to the backer board along the line.
Tiling uneven walls shower.
Things you will need measuring tape tile wet saw leveling spacers and wedges trowel thinset mortar rubber mallet grout grout float grout sponge.
When your walls are uneven and you use very thick tile which yours is it s going to happen.
With the uneven ceiling level you would normally level or laser a horizontal line that runs around the shower enclosure at the top of the tile if leaving a top border tile free see below then measure your row lines down from there to the bottom and start with any bottom trip and cuts and actually place the tile from bottom up to the top.
This is a dusty job so use plastic to cover your doorways wear a respirator that s rated for dust cover the floor with a drop cloth and make sure there s plenty of ventilation.
You still may be able to do it by removing the last tiles and redoing it.
If the shower base is uneven tiles will have to be cut to fit the last row.
Whatever you put there you are going to see the uneven tiles.
You should have used the proper substrate for your shower walls.
Find a matching thick chair rail edging 12 piece and you ll be fine.
Just get some chair rail molding or some type of 1 trim pieces.
Mine is the same way because i used 3 4 thick tile on my wall.
If any part of that should get wet you could have some issues.
You could have wrapped around the edge w the tiles for a neater look.
Begin by removing the old tile or the fiberglass shower wall.
Also tile is heavy so put down blankets to protect the floors and tub from being damaged by falling pieces.
Draw a leveled line where the bottom of the second row will fall.