Wood Panelized Roof Subpurlin Hanger Construction Defect Assessment and Load Testing to Establish Defect Tolerances

Wood panelized roof systems are a highly popular system for the construction of large-footprint, low-slope roofs, typically for single-story warehouse or industrial buildings. These panelized systems have been used for decades, commonly in the western United States. In general, large modular sections of the roof assembly are constructed on the ground, then lifted into place and connected to the primary roof support elements, which allows for rapid roof erection. In 2008, a $2\times 6$ by 3.0-m (10-ft)-long wood subpurlin fell from a building’s roof structure and landed on the floor approximately 9.1 m (30 ft) below during roof maintenance work. The building was constructed about 3 years prior to the subpurlin falling incident. The authors investigated the cause of the incident. Installation errors of the subpurlin hanger were found in sufficient quantity that the investigation grew to include a total of 21 similar buildings built by the same contractor, representing more than $\mathrm{370,000}\hspace{0.17em}{\mathrm{m}}^2$ (4 million sq ft) of roof. This paper presents the findings regarding construction defects related to hanger installation. Also presented are the results of a testing program conducted to determine acceptable tolerances for subpurlin hanger defects, with the goal of developing an efficient repair program.