In low sloped roofing systems, poorly adhered roofing assemblies are unable to resist significant wind loads and are likely to be further damaged or destroyed by wind events well below the design wind pressures for the assembly. The design and installation of rigid insulation boards are a critical parameter in the service life of this roofing assembly in that, if the insulation boards become detached, there is increased risk for complete roofing assembly failure. Foamed adhesive is a common alternative to traditional hot-mopped asphalt adhesive in contemporary roofing assemblies. The proper design and installation of insulation board roofing assemblies in foamed adhesive is paramount to the successful performance of these roofing assemblies. Some of the critical parameters that could influence foamed adhesive performance are: insulation board adhesive pattern defects; insulation board adhesive quantity; inadequate insulation board adhesive contact; and failure to maintain insulation board contact with the substrate until the insulation adhesive is sufficiently set. The present paper discusses these critical parameters through case studies that clearly demonstrate how these parameters can lead to the failure of roofing assemblies, and discusses the lessons to be learned from these insulation board adhesion failures.
Foamed adhesives are used to join roofing assembly components to the roof substrate and to each other. A variety of performance problems with foamed adhesives as installed in roofing assemblies have led to assembly failures. We previously reported, in detail, four specific failure mechanisms caused by poor adhesive installation that we have observed, and we briefly note these failure mechanisms in order to maintain continuity as we expand on our earlier work. The focus of this paper is to report on other factors that also lead to adhesive and rigid insulation board performance problems, specifically, moisture contained within the roofing assembly and substrate, which can result in the failure of the roofing assembly. Similar substrate moisture issues occur in flooring assemblies; however, whereas the flooring industry continues to address moisture-related issues that lead to adhesive performance problems, the roofing and roofing adhesive industries have been less proactive regarding use, installation, and testing for assemblies with potential moisture-related issues. We present several case studies that illustrate excessive moisture in roofing assemblies or substrates as an issue that contributed to the adhesive failure of the roofing assembly. We also discuss the lessons to be learned from not addressing these issues at the onset of a project.
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