Reports from the workers atop the roof at the time of the collapse indicated that the channel slab ‘suddenly snapped in half’ while a worker was sweeping debris off a portion of the roof in preparation for the new roof installation. No occupants were in the portion of the building at the time of the collapse. Workers atop the roof were able to get off the failing panel as it began to collapse. During the reroofing operation, debris containment netting was provided over select portions of the facility to catch small portions of spalling concrete and other construction debris that might fall through the joints between precast channels slabs during the reroofing project.ĭuring tear-off of the existing roof, a channel slab collapsed and fell to the ground.
FLASH NIGHTCLUB ROOF DECK COLLAPSE CODE
It was determined by the engineer that, absent any deterioration, the structural roof deck consisting of the precast channel slabs was generally capable of supporting the new roof in accordance with Section 705.2 of the International Existing Building Code (IEBC). There was no indication that the reinforcing steel within the precast channel slabs had debonded from the channel slabs as the distress was limited in length. Prior to the reroofing project an engineering study was undertaken, which included limited observations of the precast channel slabs, chemical and petrographic analysis of the existing concrete material, and infrared scanning of the roof to determine the approximate extent of the roof leaks. This cracking and spalling was generally isolated and extended from approximately 1 to 3 in (2.5 to 7.6 cm) along the length of the precast channel slabs.
This deterioration generally included cracking and spalling over reinforcing steel at these locations. Long term roof leaks had led to the deterioration of some precast channel slabs. The total thickness of the roof assembly varied from 14 to 18 in (36 to 46 cm) atop the precast channel slabs. A non-composite lightweight insulated topping slab was installed atop the precast channels slabs and provided support for two separate roofing systems, including various layers of insulation and roofing membranes. The channel slabs were reinforced with a single reinforcing bar in each flange (two total per channel slab) and a wire mesh within the web of the channel. Each channel slab is approximately 2 ft (0.61 m) wide and spans approximately 8 ft (2.4 m) between supports. The existing roof deck consisted of conventionally reinforced, conventional structural lightweight precast channel slabs (not autoclaved-aerated concrete). The subject facility was a manufacturing plant, originally built in the mid-1950s. In 2020 an existing roof deck experienced a partial collapse during a reroofing project.
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