No Assembly Required
Wall and ceiling contractors have long recognized the monetary advantages of steel in commercial and light-industrial framing. Now the next generation of steel framing is glittering on the job site: prefabricated computer-aided-designed steel trusses.
Designed and fabricated at a plant and driven to the job site, steel trusses are being lauded by many as the solution to redundancy, tight building schedules and space constraints in framing roofs.
A $350 million project currently underway in Dana Point, Calif., puts pre-assembled steel trusses to the test. The five-star, 400-room St. Regis Hotel, slated to open in the summer of 2001, overlooks Monarch Beach with grand style and a complicated roofline. The building called for more than 3,000 trusses on the first phase of construction alone.
Traditional building methods would have required the wall and ceiling crew to assemble C studs into trusses on the roof of the building—a daunting prospect in terms of manpower, storage, staging area and likelihood for error.
The Brady Co., the Anaheim, Calif.-based wall and ceiling contractor on the project, had experience assembling C trusses on the job site, but had never worked with a pre-assembled truss.
“The roof’s the same when it’s done,” says Todd Brady, president of the Brady Co. “However, these trusses come out built. In the traditional way, you build them on the roof and then you erect them.”
Brady says the trusses went up faster because the design made for a lighter gauge stud—18 gauge instead of 12 gauge—making the materials lighter and easier to handle than the C studs the crew were accustomed to.
Pre-assembled steel trusses do come from fabricators in C studs, as well as hat-shaped studs. But trusses for this project, supplied by Pacific Coast Truss Fabricators, were created from a Z-shaped stud, designed by Mitek Industries, of St. Louis.
Cliff Robuck, plant manager for PCTF, says the Mitek design is easier to put together than a C stud. Materials fit together in the jig easier; unlike a C shape, the Z shape lies flat and in plane.
“With C studs, each flange is usually 11⁄2 inches wide so stacking two trusses together means that the total width would be 13⁄4 inches,” Robuck explains. “With the Mitek Z shape, the finished product is only 13⁄4 inches wide when two trusses are stacked together.
“I’ve been a steel framer for 20 years and I’m used to C studs,” he adds. “This Z-shaped stud definitely has a lot of advantages over a C stud. Aside from its unique shape, it’s stronger and it takes less steel to make one of our truss chord members than a typical C stud.”
Jeanne Davenport, general manager of PCTF and designer of the more than 65 configurations required for the project, says the Z shape simplifies assembly of the trusses.
“There are three basic parts to a truss—a top chord, a bottom chord and the web chord,” Davenport says. “All three of these pieces fit together in plane on the jig table and can be screwed together easier.”
Assembly at the plant eliminates possible haphazard assembly at the job, which may be due to poor conditions, uneven work surfaces or skill deficiencies. In addition, many building jurisdictions, like the city of Los Angeles, won’t allow trusses that are assembled on site.
“We realized that there was a potential market in trusses because of the labor intensity of having to build trusses on the job site out of C studs,” she says of PCTF, which is a recent offshoot of steel-stud manufacturer California Expanded Metal Co., of City of Industry, Calif. “We can build the truss to tighter tolerances than they can in the field normally—plus or minus 1/16 inch. We are better able to control quality in the plant, thereby maintaining the consistency of the truss with its engineered design.”
The fabricators in the plant use Davenport’s CAD-produced shop drawings, which detail every piece and its location to create a truss—the longest one 60 feet. The Z-shaped studs are manufactured at CEMCO and then delivered next door to PCTF for fabrication into trusses.
“The guys in the shop are very meticulous about their work,” she says. “When they build the jigs they are very careful to make sure every truss is consistently the same so when they are erected on the site everything pieces together perfectly.”
The trusses are then shipped to the job site along with cut sheets, which include detailed drawings of each truss and specifications for fasteners at each connection point.
“We supply a full service to the contractor,” Davenport adds, “from pre-design to complete engineered stamped drawings.”
“When they come out pre-assembled, it’s like getting all the parts,” Brady says. “We do have a labor savings in assembling the trusses and the erection goes much faster because the assembly’s done under controlled conditions at PCTF.”
The Carpenters Union trained Brady’s crew to use the pre-assembled trusses, which they found generally easier to use because of the lighter-gauge steel and fewer parts.
“It takes two people to put up a truss,” Brady explains. “The clips are pre-assembled. You pre-attach the clips to the concrete and the truss is attached in place and anchored down.”
The fasteners, clips and plates that PCTF engineers into its truss system eliminate the need for welding on the job site.
“Welding is not cost effective,” says Brady, “and that’s one of the ways they save the contractors money.”
Tom Porter, executive vice president of CEMCO, says these benefits to the wall and ceiling contractor, as well as the builder, are driving demand for truss fabrication. The company has also begun to manufacture trusses at its Pittsburg, Calif., plant to meet the need.
“Typically, roof mansard construction contains a lot of heavy or light structural steel, which we are now able to replace with load-bearing steel trusses,” Porter says. “That allows the general contractor to deal with only one framing contractor on the roof. It saves schedule time and it saves the owner money.”
Porter acknowledges that steel trusses are not new to the market, but says new developments are paving the way for more companies like CEMCO and PCTF to supply them to the wall and ceiling contractor.
“Over the years, there have been attempts at pre-fabricated trusses,” he says. “The need was overshadowed by the lack of technology to support the product. Advances in the building codes, along with software development and computer-aided design, are now allowing the use of steel trusses to meet their potential.”