During construction of buildings with large and continuous roof decks utilizing wood structural panels, roof sheathing panels may be subject to accumulated deck expansion when exposed to elevated moisture or humidity. Panel expansion may accumulate through the roof framing and sheathing. Field experience often reveal the presence of build up of expansion in roof decks, even though proper spacing gaps have been provided at panel edges and ends, and panel movements have been restrained by fasteners and framing.
It is recommended that building designers and/or contractors incorporate a temporary expansion joint in the roofs of a large building to avoid panel ridging, buckling and out-of-plumb displacements when the roof plan dimensions exceed 80 feet. An example of a temporary joint for a large roof deck using wood structural panels may be provided by sheathing 80-foot sections and omitting a roof sheathing panel in each sheathing course at 80-foot section intervals (Figure 1).
Figure 1
Location of temporary roof expansion joints for light-framed wood and steel structures, when the roof plan dimension (length or width) exceeds 80 feet in one direction.
After the installation of 80-foot sections is completed, install the cut-to-size “filler” panel at the omitted panel areas for the temporary expansion joint (Figure 2). Installed roof deck panels should be covered with roofing underlayment as soon as possible for protection against wetting and moisture.
Figure 2
Suggested construction detail for roof temporary expansion joint.
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