Jim Finlay, the owner of Archadeck of Suburban Boston, introduced Coastal Connection to an interesting technique last month: the use of LiteSteel cold-rolled steel beams to frame long-span support girders for a backyard deck. Archadeck has an interesting business model: it’s a national franchise with more than 70 members nationally and worldwide, focused on the backyard outdoor-living market. The national firm, headquartered in Richmond, Va., supplies marketing and technical services, including engineering analysis of structural assemblies when needed. But local franchisees have broad latitude to run their own businesses. For example, Archadeck supplies local branches with a comprehensive book of structural assembly and fastening details, all vetted by the company’s engineers. However, as Jim Finlay pointed out, many of those details were originally developed by members in the field who needed a structural solution for a particular situation. Using LiteSteel for a long span is Finlay’s latest instance of that process. It was his own idea to include the beams in his designs, and he’s working out the details as he goes — but with help from Archadeck, as well as from the engineers at LiteSteel. (LiteSteel posts span tables and design software at this “ Tools and Resources” link.) Coastal Connection visited two of Finlay’s jobs to see how he’s using the steel. One deck was attached to the main house, while the second job involved a free-standing structure (used to avoid the problem of tying a structural ledger into a brick veneer exterior). In both cases, the purpose of the LiteSteel beam was to enable the framers to create a wide, tall opening under the forward edge of the deck, for an easy walking and viewing transition from the under-deck patio to the back yard. With the free-standing deck, traditional sawn lumber was reaching its limits even for the shorter spans of the beams next to the house, says Finlay. “My posts next to the house were spaced at about 11 feet apart,” he explains, “which worked well for not blocking any windows. And for those beams with the 11-foot span, I specified triple 2x12s — and that’s about as far as I would want to span with 2x12s.” For the front beam span of 18 feet, Finlay looked at the option of a steel flitch plate sandwiched between two 2x12s. But even with a 3/8-inch steel plate, the beam would barely span 13.5 feet — and even at that length, the assembly would be a bear to put together and a strain to lift into place. But a LiteSteel beam capable of the 20-foot span would weigh only 10.8 pounds per lineal foot — light enough for two men to place by hand and requiring no assembly (see photo below by Jim Finlay). The LiteSteel beam, with its innovative C shape, is lighter than a comparably strong red-iron I-beam, because the concentration of material in the curled top and bottom flanges uses the material more efficiently. In the Boston area, LiteSteel beams are also less costly than a custom beam built up of wood with a steel flitch plate, Finlay says. The crew did have to invest some time in learning and installing a few out-of-the-ordinary connection details. To provide nailing for diagonal bracing, carpenters have to pack out the void in the steel beam using sawn lumber blocks. And to tie the deck joist system to the steel beam, they used Simpson H series wind uplift connectors attached with hex screws. (Even though the screws have a self-tapping cutter tip, the crew had to pre-drill the steel to accept the screws.) Above, carpenters install blocking for wooden diagonal bracing into the steel beam channel. Below, they screw Simpson framing anchors to the steel beam. (Photos by Ted Cushman) For fastening the blocking and the beam to the solid wood support, Finlay’s crew used another innovative product: FastenMaster’s new ThruLOK Screw Bolt Fastening System. Like the other self-tapping structural screws in the FastenMaster LOK lineup, this hardened steel fastener installs without pre-drilling and carries a rated load capacity. But ThruLOK also includes a specially designed cap nut that turns the screw connection into a bolted connection, for a significant boost in strength. The carpenter sends the screw through the wood with a cordless impact driver until the tip emerges on the far side of the joint, then places the cap nut over the end of the screw, twists it down by hand, and spins the screw again with the driver until the nut locks itself down tightly with friction against the beam or post. It’s a quick and easy replacement for an old-school bolted connection. With the LiteSteel beam, however, the carpenters have to pre-drill a hole for the ThruLOK in the beam using a hardened drill bit: the ThruLOK’s self-tapping end, like the hanger fasteners, won’t drill through steel. Above, the ThruLOK system consists of a self-tapping hardened screw, a washer, and a special lock-nut with wings for the carpenter to hold and rough nubbins to help lock the nut down by friction against the wood. No wrench is needed — just the drill/driver or impact driver. Below, carpenter Rick Santos sends a screw into wood blocking; bottom, Santos applies the locknut by hand. (Photos by Ted Cushman)
