Slipforming, a method formerly associated primarily with the construction of concrete bins and silos, is now used for tall slender chimneys, bridge piers and communications towers, as well as more complex structures such as caissons, nuclear containment vessels, tapered cooling towers, offshore drilling platforms and buildings of all types. Although slipforming is by no means a stranger to the concrete construction industry, its use in forming the primary the primary walls of high-rise reinforced concrete buildings has been infrequent, compared to more conventional methods of forming. There are several reasons why slipforming has taken a back seat despite its great potential for speed and economy. The first involves the design of the building, which must be coordinated with the use of slipforms at the earliest stages. When the architect or engineer leaves construction considerations entirely to the contractor, the configuration of the building may turn out to be too complex for slipforming, thus forcing the contractor to abandon the method in favor of some more conventional system. A second inhibiting factor has been the difficulty of forming and casting floors sufficiently fast to keep up with the rapidly rising slipformed walls. Unless an efficient sequence for floor construction is worked out, the economic advantage of slipforming the walls can be largely lost. Huge flying forms were used to expedite the forming and casting of floor slabs. With these forms, which varied from 9 to 14 feet wide and 30 to 53 feet long, the contractor was able to cast an entire bay form the central hallway out to and including the balcony all in one operation.