Sagging roof surfaces and broken sub-purlins can be the result of construction defects to wood panelized roof systems; however, roofs with no signs of failure or distress may still be degraded to the point of detachment and failure. Although a detachment of an individual purlin may not result in the collapse of the roof or even a portion of the roof, it may represent a potential life safety hazard to the occupants of the building. This paper will discuss the design, construction, and failure of a sub-purlin hanger at a large warehouse that resulted in the investigation and remediation of over (370,000 square meters) 4 million square feet of warehouse roofs. This paper will present the viewpoint of an investigator working for the building owner/developer (WJE) and the viewpoint of an investigator working for the roof framing subcontractor's insurance company (DC). The factors involved during the original design and construction will be discussed as well as the methods used to determine the adequacy of the remaining sub-purlin hangers. Although the paper does not offer a formula for identifying hidden failures, it demonstrates that a process can be implemented to reduce future sub-purlin hanger failures to an acceptable level.
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