Spray Applied Polyurethane Foam Roofing Adhesives
Low-rise, two-component expanding polyurethane foams are becoming ever popular as roofing adhesives to adhere EDPM membranes directly to the roof deck, for a totally non-penetrating, fastener free, roof system application.
These adhesives are more commonly used as a composite system to adhere foam boardstock insulation to the roof decks. Once the insulation board has been fully adhered, the adhesive is spray applied again over top of the foam board, to glue/fasten the EDPM membrane to it. This now creates a total composite insulated and sealed roof sytem.
Both standard or specialty designed proportioning pumps are used to deliver a Part A, and Part B, polyurethane foam system to the spray gun. These proportioning systems can be either heated, or non-heated depending on the particular system in use, and outside ambient temperature. A catalytic reaction takes place, causing the adhesive to expand or foam.
The EDPM membrane is then laid into the foamed adhesive after developing a string/body cure characteristic and rolled with a weighted roller to ensure proper adhesion. Usually within 15-25 minutes, the polyurethane adhesive cures to form a tenacious bond between the substrate and the membrane, and/or the substrate, insulation boards and the membrane.
R-ValueEach layer of polyurethane adhesive is typically 1⁄16"- to 1⁄8"- thick and can further provide redundant waterproofing characteristics to the roofing assembly. The expanding nature of polyurethane polyurethane adhesive also provides some additional R-value per layer. When specified for insulation attachment, thermal bridging of mechanical fasteners is eliminated The National Roofing Contractors Assocation (NRCA) estimates a 3-8% loss in R-value.
Polyurethane adhesive also helps seal the insulation joints while avoiding the loss of up to 10% of the R-value. This also maintains and enhances the integrity of the roof deck. Many systems use water is used as the blowing agent, making it CFC free and non-ozone depleting.
Superior Wind Uplift Ratings
Adhesive roofing systems from many suppliers can boast superior wind-uplift resistance delivered with code rated assemblies ranging from FM 1-90 up to FM 1-990, Dade County, UL 1897, and UL 580 approvals. As a result of this exceptional wind uplift performance, these systems commonly offer up to 80 mph standard wind speed claims that can even be upgraded to 120 mph with certain design enhancements.
Quick Installations Without Disruption to Building OccupantsDue to the relatively low noise and low odor associated with application, adhesive roofing systems are an excellent choice for reroofing occupied buildings. The spray application process can significantly reduce labor, and large workforce disruption. Project completion normally occurs in a timely manner.