Three midcentury forces converged to form the truss business we know today. First came the deluge of demand for affordable housing after World War II. Then came the prefabbers who addressed that need with trusses. And finally came the connector that made trusses into a blockbuster product.
Fifty years before the advent of the truss plate, panelization began to take shape in the precut house packages promoted by Sears and others. Gradually, through the course of downturns and wars, wall panelization companies, known as prefabricators, arose and developed systems that answered the dire need for affordable post-World War II housing. By 1950, nearly all prefabbers had added trusses to their packages to expedite roof framing. Looking back, you would think that one of these firms would have discovered a better way to join truss members together. But perhaps they were preoccupied with sourcing, packaging, and fitting the wide range of materials, from framing to furnishings to furnaces, into their open-top vans. Or perhaps they were too busy expanding their facilities to keep up with skyrocketing demand. In any case, trusses weren’t much of a concern, because they were repetitive and easy to nail together using scrap pieces of plywood. However, the reasons trusses worked well in most of the country did not also apply in South Florida.
Because builders in hurricane-prone regions didn’t build wood-framed walls, the prefabbers’ preference for trusses didn’t apply there. Instead, it would take the work of two determined professionals discovering better truss connectors to further commercialize the use of trusses. The first to get involved was Cal Jureit, an engineer who worked in a testing lab in Miami, FL. After five years of increasingly destructive hurricane seasons, local building officials called on Jureit to help them develop more hurricane-resistant construction standards. From this collaboration came the requirement that new truss designs be subjected to full-scale load tests, and also the specification that higher design loads be used.
To withstand the full-scale testing, the critical element was the performance of the truss connectors. These stringent new standards precluded the use of plywood gussets. Initially, the only acceptable alternative was the split-ring connector, but builders disdained this option and needed a better alternative.
The timing of these tougher requirements couldn’t have been more unfortunate. New housing backlogs in South Florida far exceeded those in most of the country, as the supply of available dwellings had been reduced by 15,000 by recent storms, and the demand was greatly increased by the continuing arrival of Cuban refugees. Fortunately, an architect named Carol Sanford, who worked for the H-Brace Company, was hot on the trail.
In the midst of this frenzy, Sanford contracted with Jureit’s lab to test a truss connected with nailed-on flat metal plates. Although this design met code requirements, it required hundreds of nails to be hand-driven into pre-punched holes, because nail-guns were not yet available. Later, Sanford submitted a truss built of glue-laminated wood members, but neither he nor his company pursued this approach further. Finally, Sanford brought in a truss connected with metal plates that contained wedge-shaped teeth and nail holes, which seemed to perform adequately. Apparently, Sanford no longer represented the H-Brace Company and applied for a patent in his own name, after which he began commercializing his Grip-Plate in 1954. [For images, See PDF or View in Full Issue.]
Meanwhile, the H-Brace Company, whose owner and president, Edward Wadsworth, was an accomplished civil engineer, applied well-established wood engineering principles to greatly increase the strength of his proprietary connectors. The most impactful was the clinching of nails, which was accomplished by notching them and chiseling their points so that they would bend toward the notch when striking the steel surface of a truss table. This clinching would more than double the strength of each nail, since each nail would act in double shear. Not only would this connector require less than half the number of nails, but it would only need to be fastened from one face of the truss, eliminating the need to flip the truss.
The H-Brace design, superior to Sanford’s Grip-Plate in many ways, was the first salvo fired in the long competitive struggle for the best connector. This H-Brace design would work well at Karl The Losen’s Ridgway Truss in Florida and the late Vivian Hollinshed’s plant in North Carolina. However, the undesirable task of hand-nailing hundreds of fasteners would soon succumb to the modern connector, as Cal Jureit reentered the fray testing the strength of his own invention next.
Next Month:
The Great Connector
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