When i tile diagonally on a wall i always use a straightedge in the middle of the wall.
How to lay tile diagonally wall.
Using a wet saw cut one tile into a triangle diagonally from opposite tip to opposite tip.
If you are laying the diagonal tiles over the entire backsplas simply drawing a chalk line from one corner to the opposite will not work.
Lay half of first tile with cut side facing 90 degree corner and tips almost touching walls at a 45 degree angle.
Because tile laid on a diagonal has half tiles or pieces of cut tile along each edge of the installation a lot more tile is required to complete the job.
Lay out tiles in a dry run to make sure they fit.
Diagonal tile installations draw the eye out to the sides of the installation visually widening and enlarging the space.
This is a fold.
Install tiles one through four as directed.
Dry fit a row of tiles along each diagonal line.
The best way is to arrange your wall tile in a pyramid shape.
There are only two ways to handle an inside corner with diagonal tiles.
If it seems complicated try this.
Then every subsequent row is a process of draping over the pyramid back and forth.
While a diagonal pattern might seem logical if you are using big tiles for an expansive space such as a large kitchen or great room floor many people worry that diagonal tiles can look too busy in a smaller bathroom and if you are a diyer planning to install the tiles yourself you might worry that.
If the wall is really large i use a square to keep the corners lined up.
Start in a 90 degree corner.