For more than 40 years, the Colorado State Bank and Trust building has stood sentry at 1600 Broadway, ushering financiers, artists, retailers and tourists alike into Denver’s thriving central business district. However, its brown, rocky façade—considered chic and contemporary in 1972—has cut a less-than-impressive profile in recent times.
To bring the building up-to-date, Denver’s Gensler architectural team needed to replace the aggregate precast cladding with a cladding solution that was lightweight and would not affect the building’s structure. They specified the sleek and modern Reynobond aluminum composite material (ACM). “Our main programmatic goal for the project was to renovate the exterior appearance with a lightweight material that wouldn’t affect the structure. Metal was a good choice—it wrapped the existing shape and form of the building well, it has the right aesthetic and it provided an economical solution for the retrofit,” says Jeff Hall of Gensler.
Not only did the Reynobond ACM deliver the desired lightness, formability and price point, but the material also blended with a partial metal over-clad of Reynobond panels that had been added to the base of the building in 2003. Alcoa Architectural Products was able to match 120,000 square feet of 4-millimeter Reynobond ACM with a fire-retardant (FR) core, finished with Anodic Satin Colorweld 500XL, to the existing 11-year-old panels, even though the existing color was no longer a stocked finish.
Elward Systems Corp. (ESC) of Lakewood, Colo., engineered an adjustable, two-piece clip, sub-frame system to secure the Reynobond ACM panels, enabling them to plumb up the building from the concrete columns, which were not completely true, and to shim some things to straighten them out. The panels were used to encase the existing columns of aggregate concrete, as they could not be attached directly to the aggregate stones.
From floor to floor, the individually installed Reynobond panels averaged about 3 by 12 feet in size and were for the most part repetitive, with only the first and last ones being different lengths. At the top of the building, the cornice required hot air welds and custom fabrication to create the shape, creating the illusion that the columns are holding up the crown of the building. Those panels were formed with radius cuts and welded together. And because the building was already weathertight, Gen3 Architectural Wall Systems of Denver, installed the Reynobond ACM panels in an ESC rout-and-return pressure equalized rain screen system.
The worksite itself was small and in a highly trafficked area. To ensure that pedestrians were not endangered by falling concrete loosened by workmen installing the sub-frame system, much of the preliminary work was done at night and on weekends. Nine U-shaped swing stages were used to access the columns of the structure, along with seven standard modular platforms that were used to feed the materials to the stages. Crews of 25 to 30 people worked in two shifts to complete the project in six months.
The end result? A lighter, brighter Colorado State Bank and Trust and a contemporary landmark for the city’s commercial hub.