hierarchical dimension lines are placed 1/2" from each other. The innermost dimension, the opening dimension, are 1” to 1-1/2” away from the plan, never touching it.
The text of the dimension is always written on the top or left of the dimension line. Extension lines are used to bring the dimension line a distance from the object so it is easily read and not confused as part of the object. The extension line starts about 1/16” from the edge of the object, never toughing it. And it extends about 1/8” past the dimension line. At the intersection of the extension line and the dimension line is a “tick.” The tick mark on a dimension line is an important detail and crosses at a 45 degree angle at the intersection of the dimension and extension lines. It is typically 1/8” long, however this may vary with the size and scale of a drawing. Use your best judgment, but typically a tick mark is the length of the overlap of the dimension and extension lines (for example if you overlap the lines by 1/8” then the tick mark will be 1/8” in length). The height of dimension text is typically between 3/16" to 1/8", but not below 3/32” when printed. This assures its readability. Dimension text doesn’t touch the line. See Figure 28 for an example.
Figure 28. Dimension techniques for floor plans