Spray polyurethane foam- (SPF-) based roof systems are
constructed by mixing and spraying a two-component liquid that
forms the base of an adhered roof system. The mixture expands 20
times to 30 times its liquid volume and forms a closed-cell foam
insulation. An elastomeric coating usually is applied to the foam
insulation and provides the long-term weatherproofing
characteristics of SPF-based roof systems.
Polyurethane foam flashings with elastomeric coatings, as
depicted in the detail, are sprayed in place and become an integral
component of an SPF-based roof system. SPF forms a monolithic,
continuous, self-adhered flashing detail. At skylight penetrations,
SPF is applied to form a fillet or cant at the base of a skylight
curb and then is applied up the vertical surface to a desired
flashing height. A polyurethane foam flashing detail requires an
elastomeric coating up the curb and above the termination line of
the SPF.
At skylight curbs, the SPF should terminate a minimum of 6
inches (152 mm) above the horizontal SPF roof surface with the
elastomeric coating extended a minimum of 2 inches (51 mm) above
the SPF.
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