Medford, Oregon- A newly released independent engineering report has identified two critical structural deficiencies that led to the catastrophic collapse of the gym roof at North Medford High School earlier this year, concluding that the incident was primarily the result of outdated design assumptions and flawed manufacturing in the building’s original construction.
The findings were unveiled Thursday by KPFF Structural Engineers during a scheduled Medford School Board work session. The firm had been commissioned by the Medford School District to conduct a comprehensive forensic analysis following the collapse of the main gymnasium roof on February 11, 2025.
The 140-page report details a timeline of the structural failure, which began with the cracking of glulam beams on February 7. The progressive collapse culminated four days later, when multiple long-span timber beams failed in sequence, bringing down the entire main gym roof.
Manufacturing Defect and Design Overestimation Identified
According to the report presented by Katie Ritenour, PE, SE, Senior Associate at KPFF, two main causes were responsible for the failure:
Scarf Joint Delamination in Glued Laminated Timber Beams The long-span beams that supported the gym’s low-slope roof were manufactured using scarf joints—a once-common method of splicing timber lamination in the 1960s. Investigators found that the collapse was initiated at these scarf joints, where glue failures led to delamination. These joints were particularly vulnerable to tension stress and have since been replaced in modern construction by finger joints, which are significantly more reliable. Overestimated Structural Capacity Based on 1960s Standards The gym, constructed in 1965, was designed based on now-outdated assumptions about the strength of deep glulam beams. Specifically, the original design anticipated a flexural capacity that has since been downgraded by 25% under current engineering standards. When adjusted to today’s codes and safety factors, the beams were found to be overstressed under even normal dead loads—let alone additional snow accumulation.
“These two contributors led the roof glulam beams to be overstressed under the roof’s total dead loads, providing limited ability to support additional roof live or snow loads,” the report states.
Snow and Basketball Hoop Identified as Minor Contributors
The failure occurred amid a February storm that dropped more than six inches of wet, saturated snow on the structure. KPFF’s modeling estimated the snow load at between 12.5 and 25.9 pounds per square foot, depending on moisture content. Although the structure was not originally designed with snow loads in mind, the engineers determined that the snow alone was not sufficient to cause failure—but did exacerbate the existing structural weaknesses.
Investigators also noted that a basketball hoop and backstop had been mounted to the two beams that first failed. Although no structural drawings exist for the hoop installation, the equipment was likely installed between 2008 and 2010 and may have caused localized stress concentrations near the scarf joints. KPFF concluded that while the hoop may have contributed to the failure of Beam A, it was not a primary factor.
Retrofit Work Not to Blame
Importantly, KPFF found no evidence that the district’s 2024 seismic retrofit project contributed to the collapse. That project, which included new perimeter shear walls, diaphragm reinforcement, and a new roof membrane, actually reduced the overall superimposed dead load of the gym roof due to lighter modern materials.
The analysis also found no signs of decay in the timber beams. Probes and resistograph readings from beams recovered on site showed only surface-level staining, with no evidence of water damage or rot. “It is our opinion that decay of the glulam beams was not present, and therefore not a contributing factor to the beam’s failure,” the report states.
Collapse Mechanism: Progressive Structural Failure
The collapse followed a classic pattern of progressive failure, beginning with the overstressing and cracking of two central beams. As these failed, the load was redistributed to adjacent beams, exceeding their already compromised capacities. Within hours, the entire roof structure gave way.
While not typically accounted for in the design of K-12 school facilities, progressive collapse is a known phenomenon that occurs when an initial local failure triggers a domino effect. KPFF noted that the 1965 design met the standards of its time but would not have provided sufficient redundancy under today’s understanding of structural risk.
District Responds with Broader Structural Review
In response to the incident, the Medford School District has initiated a full assessment of all large-span structures across its portfolio of facilities. This third-party review will inventory roof systems—including material type, beam spans, and structural age—and identify buildings that may require reinforcement or monitoring.
“These proactive measures will support the ongoing annual monitoring of district facilities to enhance safety and resilience,” the district said in a statement.
The report offers a sobering reminder of how evolving standards in structural engineering can dramatically alter the performance expectations of legacy buildings. While the gym had stood for nearly six decades without reported structural concerns, the interplay between outdated design assumptions and hidden manufacturing defects ultimately proved fatal to the structure.
Despite the collapse, KPFF emphasized that glued laminated timber remains an appropriate structural solution for gymnasiums, provided modern materials and manufacturing methods are used. “The use of glulam beams was an appropriate choice,” the report concludes, “and remains a viable option for gymnasiums with similar spans and loads today.”
No injuries were reported in the collapse, and the gym was unoccupied at the time. Here is the link to Medford Alert’s full coverage of the incident.
Source: MSD549C
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