Case Studies of Adhesive and Rigid Insulation Board Failures due to Moisture in Low Sloped Roofing Assemblies

ABSTRACT: 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.

KEYWORDS: foamed, adhesive, insulation, moisture, roofing

Introduction

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

[1] , 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 negatively impact adhesive and rigid insulation board performance, specifi­cally, moisture contained within the roofing assembly and substrate, which can result in failure of the roofing assembly. We present several case studies and a sum­mary of hygrothermal computer modeling that exemplifies such roofing failures. We discuss the consequences of trapped moisture within the roofing assembly and its effect on roofing component adhesion. 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 adhesive use, in­stallation, and testing for assemblies with potential moisture-related issues.