The slipform technique is used to construct cylindrical, square, or irregularly configured concrete structures. Hoffmann’s standard chimney design uses a cylindrical shape. Specific chimney design is based on many requirements from the customer, EPA, FAA, underwriter laboratories, and site specifications. Once the design criterion is defined, Hoffmann then configures the chimney as plumb or tapered while also considering construction costs. Plumb chimneys typically have constant inside diameters with outside wall thickness varying to meet strength requirements. Tapered chimneys have a gradual reduction in diameter and wall thickness to a narrowing top. The reduction in diameter and wall thickness can reduce foundation loads and construction costs in high wind and seismic areas.