Two-Part Vertical Block
In its mature form, the two-part vertical block began to be used during the late 19th century as a means of simplifying the exterior composition of tall commercial buildings. Reflecting the academic movement’s concern for order and unity the facade is divided horizontally into two major zones that are different yet carefully related to one another. The lower zone rises one or two stories and serves as a visual base for the dominant “shaft,” or upper zone. Many large two-part commercial blocks built during the early 20th century were treated in a somewhat similar manner. The essential difference between the two types is the size of the upper zone and the emphasis it receives. The two-part vertical block must be at least four stories high to possess a sufficient sense of verticality. It is further distinguished by a clearly prominent upper zone, rather than appearing merely to have several stories placed atop the lower zone; in addition, the upper zone is treated as a unified whole. The type is most commonly used for office buildings, department stores, hotels and, occasionally public and institutional buildings. (Longstreth, 1987, 2000 )