In organisational analysis, the terms flat and tall are used to describe the levels of spans of control in a hierarchy of management. .
The tall structure includes a hierarchy of many levels and with very small or narrow spans of control. It produces very close supervision and very careful control. Power is held at the top and is shared among a limited number of individuals (Griffin & Moorhead, 1995). Individuals on top are depended on for skill, initiative, and daring, and individuals at the bottom have very little say in decision making. Hanna and Wilson have noted that classical bureaucratic structures are typically very tall (1988).
The hierarchy of a flat structure has fewer levels than that of a tall structure and its power field is much broader. A flat structure tends to be rather loose in terms of control and supervision - more individuals report to a single supervisor, and each individual has more independence in decision-making. .
Amongst discerning factors that separate what is flat and tall is the amount of communication that passes through an organisation. Hanna and Wilson established that in a tall structure, downward communication flows from the top toward the bottom in an expansive fashion, but upward communication from the bottom to the top is restricted (1988). The greater the number of levels in the hierarchy, the greater the tendency for upward and downward communication flow to be distorted.
The communication problems that derive from a flat structure have to do primarily with information overload (Hanna & Wilson, 1988). Since the individual supervisor's span of control is much greater, he or she has to process many more messages from subordinates than a manager who has a far more limited span of control in a tall structure. Also, an increased span of control, with the consequent increase in information, tends to decrease task efficiency because it decreases role specialisation.
