Roof expansion joints are used in roof systems to minimize the
effects of stresses and movement of a building's components. Roof
expansion joints prevent building stresses from splitting,
buckling, ridging or damaging a roof system.
The expansion-joint detail for single-ply membranes has evolved
through the years. The first expansion-joint detail appeared as
Detail K-1 in the second edition of The NRCA Roofing and
Waterproofing Manual published in 1985. This detail depicted an
expansion joint specifically for PVC membrane roof systems. The
expansion joint was constructed out of two wood nailers that
essentially were sized to be the same height as the roof
insulation. Compressible insulation was installed between the
nailers. At the top surface, the joint was filled with flexible
tubing and capped with a PVC flashing strip welded to the membrane
on each side. The flexible tubing and flashing strip accommodated
the expected movement.
The detail remained the same in the manual's third edition
issued in 1989.
In 1995, the manual's fourth edition divided single-ply membrane
roof systems into two categories—thermoplastics and
thermosets—and the expansion-joint detail was shown in...
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