Although last month’s article in this series, “Home Building Technology, Part V: Early Truss Connection Innovators,” brought our story up to the post-war time period, we would be remiss without acknowledging the original truss manufacturers in greater detail. A small group of fabricators dominated the wood truss business for twenty years, but they seldom have been given their due and their work has been largely forgotten. Their product arose out of the depression, aided us in the war effort, and garnered wood a much larger role in the construction economy. The connector they used, the split-ring, led to their success as well as their replacement. Even so, while the split-ring connector has been much disdained, the large commercial and residential applications of that time elevated wood engineering practice, and transitioned us to today’s modern truss plate technology. [For all photos, See PDF or View in Full Issue.]
The split-ring was discovered when lumber sales in the U.S. had dropped by two-thirds during the Great Depression, and two executives of the National Lumber Manufacturers Association (NLMA) went to Europe seeking other ideas to improve sales. They perhaps went there with the realization that Europeans were the first to raise huge structures using wood, such as the classic cathedrals, many of which were built before our country was born and are still standing. Surprisingly, in a Germany wracked by the ascension of Hitler to power in 1933, they discovered the first wood connector that could carry the maximum load that the wood members could sustain.
NLMA’s Board, comprised of timber industry titans, was determined to reverse the downward trend of wood’s market share of construction spending. Because most of their product was consumed in home building, which was not expected to recover in the near term, their only option was to pursue governmental and commercial work. To this end, the NLMA created a wholly owned R&D-oriented entity, The Timber Engineering Company (TECO), to exploit split-ring technology as well as other advances. They wisely chose Washington, D.C. as their headquarters to take advantage of the vastly increased government spending being initiated there, and they followed the lead of their largest member, Weyerhaeuser, in engaging in lobbying efforts.
To make the most out of the split-ring, they recruited a team of experienced civil engineers, who couldn’t have been difficult to find in 1935. These professionals first tackled the meager amount of work that was available to them, which came from the Works Progress Administration’s (WPA) job-creating programs and the Public Works Administration’s (PWA) low-income housing projects. Because these government entities specified that much of their work was to be demountable, wood trusses became the best alternatives. By 1938, NLMA members and other independents had fabricated trusses in nearly every state based on designs such as the one shown. Although designed to be demountable, few were disassembled, and this project in Columbia, South Carolina, with 16 buildings encompassing 280 units, continued to serve low-income residents for 79 years until it was razed and replaced in 2017.
After residential work, TECO engineers then turned their attention to commercial structures. Their amazingly detailed work was captured in their publication, “Typical Designs of Timber Structures.” This 141-page looseleaf manual was distributed at no charge in 1940 to 45,000 members of the building industry. Several of the included designs were accompanied with “as built” photos, although their intricate details cannot be fully appreciated from these now 86-year-old photos.
Although the initial publication of this manual occurred four years before the NLMA released its first National Design Values for Wood Construction (NDS), it was in full compliance with the values therein. Included were bow string trusses for airport hangers, arena roofs spanning up to 200’, and several sloping flat trusses for factory and warehouse roofs.
One of the most creative designs, intended for stadium grandstands, was said to be adaptable to many different venues and “may be extended… and may be used with and without roof.” This design “has been widely employed in the U.S. and Canada…and all have reported favorably on the strength and economy.”
Not shown in the manual was the design for the U.S. Navy’s blimp hanger, of which 17 were constructed during World War II. These were the largest wood structures ever built in the U.S. at 178’ tall, 300’ wide, and 1000’ long, covering 5½ acres. At least one still stands in Tustin, California.
In the early 1940s, when many war-related factories were being built, sawtooth roofs had become popular, with windows installed on the verticals members to provide light for operations. Also shown in the manual were three-hinged arches and water towers with access ladders.
The largest wartime application of the split-ring was for the hundreds of structures built on military bases, and the thousands of houses for workers at war materiel factories (for more on this, see “Truss Tales: How Wood Trusses Supported the War Effort and Helped Expand the Components Industry”). All of these wood structures “released steel in enormous quantities for war needs,” according to a Weyerhaeuser ad.
Split-ring trusses enjoyed one major advantage over current technology. The width of their cross section was at least three times the width of a single-ply plated truss. And in the case of long spans, 3-1/2” wide lumber could be used, adding even more to their stiffness in handling and their stability during erection. However, the complexity of fabrication could be overwhelming.
When housing became a high priority after the war, TECO focused on much smaller spanning trusses. They claimed to have supplied connectors for 200,000 housing units and many commercial buildings for which they sold $18 Million in connectors by 1957. As examples, TECO supplied luxury residences in California, a home built in 24 hours in Toronto, and a 5000-truss job built for a sprawling suburban St. Louis subdivision.
Despite their apparent success up to 1957, that year brought ominous developments for TECO in Miami. An aggressive salesman for a builder introduced a nailed-on steel plate connector to that market that was rapidly displacing most of TECO’s business. That plate was offered at a considerably lower price, and fully assembled trusses could be delivered to any site. When TECO discovered their unexpected loss of sales to another connector in one of the strictest building code areas of the country, they surely realized the magnitude of this threat. However, by that time, the threat had tripled. Not only had that salesman, Carol Sanford, begun taking TECO’s sales in other markets, but two other South Florida firms were offering connector products that were said to require no additional nailing.
As the building community embraced the overwhelming advantages of the modern truss connector beginning in the 1960s, the use of the split-ring gradually declined. In 1992, TECO sold their fastening and connector division, and the largest of the split-ring fabricators, American Roof Truss, ceased operations. On rare occasions when split-ring trusses continued to be specified, usually for architectural applications, truss plants quickly discovered, as I did in Texas in the 1980s, that they are exceedingly difficult to fabricate, encouraging the quest for alternatives, and giving rise to a whole new industry.