Sorry, bit late to the party on this one, but here goes:
BS5385 part 1-2018 - 7.1.5 Setting out
Unsightly cut tiles should be avoided and joints should be of a uniform width, true to a line, continuous without steps: allowance should be made for an adequate width of joint. Cut course, both vertical and horizontal, should be:
a) kept to a minimum
b) determined in advance
c) as large as possible
d) arranged in the least prominent locations
Where wall surfaces are interrupted by features, e.g. windows, access panels or
sanitary fittings, the
tile fixer should seek guidance from the designer as to the setting out to be adopted; similar guidance might be required in the positioning of movement joints, since they are predominant and could determine the setting out pattern.
Horizontal joints and cut courses should be positioned depending on several factors, of which the following are examples.
1) Tiled areas that adjoin or are adjacent should be set out so that horizontal joints are aligned
2) The upper and/or lower extremities of the wall might not be level, requiring a course or courses to be cut with a raking edge. Wherever possible, the horizontal joints should be positioned so that the whole of the rake can be taken up within the height of the tile in the cut course.
3) If it is thought desirable to align a joint with a feature, this becomes the setting out point and might initiate the need for, and frequently dictate the location of, cut courses elsewhere.
4) To ensure the rows are truly horizontal, a level line should be established to position the starting course. This line should be continuous across all
tile surfaces.