Rectangular proportion has always been analyzed by the fact that a diagonal of a rectangle can be used to keep other sizes of rectangles in proportion to it. When such diagonals line up, th e rectangles relate proportionally and the visual result is pleasant or harmonious. There is another proportioning system based on the human body. This makes sense, since humans are to live in and use the building. Repetition means some patterns should repeat continuously.
Balance is when opposing forces or weights are equal.
This is also true in architecture. When the smaller portion is further away from center, it can balance a larger or heavier portion. In art thi s is known as informal or unequal balance. If something is identical on both or all sides of the center, it has a formal balance. Sometimes things are balanced all about a center, and that is called radial balance.