Cover Story Lightening Up on Concrete Cladding Less is more with thin precast/steel stud hybrids By Moffette Tharpe, Robert Bouchard, CPCI, and Michael Chusid, RA, FCSI here was more than half a metre of snow on the ground—the kind of weather when construction crews hate jockeying truckloads of precast concrete panels into position under a crane. However, on the jobsite of Montreal’s Hilton Garden Inn, it was worth the effort because every truckload covered a large expanse of wall. There were more panels per load than a truck usually carries, and some were 9.8 x 3.2 m (32 x 10.5 ft)—a size generally impractical with conventional precast architectural concrete. However, even these surprisingly large panels weighed less than 4600 kg (10,141 lb). These panels were studcast precast architectural concrete. With 50 mm (2 in.) of concrete thickness, mated to a panelized frame of heavy-gauge galvanized steel studs, such products could enclose a wall two to four times as quickly as conventional precast, sealing out freezing weather and thereby speeding up construction on the building interior by weeks. In the eternal struggle between building cost and quality, these studcast systems can be potent tools. The thin-panel system provides benefits of architectural precast concrete, but reduces weight by more than 50 per cent. The light weight leads to cost reduction that multiplies through every level of the superstructure, into the foundation. Building with studcast panels saves time, tends to be lighter on the environment than conventional panels, and offers performance advantages. Weighing the options Architectural precast is known for esthetic versatility, durability, affordability, speed of erection, and, unfortunately, its great weight. Typical 150-mm (6-in.) thick panels tip scales at about 350 kg/m2 (70 lb/sf), and carry none of their own load. Some precast is even thicker and heavier, hanging on building frames, needing a weighty superstructure for support, which then demands a heavy T Photo courtesy Hilton Garden Inn Montreal 8 January 2010 Construction Canada CC_JanFeb10.indd 8 12/22/09 11:55:22 AM