Case Study: The Critical Role of Sealants in the Repair of a Fluid-Applied Roofing Membrane

Abstract

Harsh tropical climates of Guam impact the selection, installation, and performance of roof membranes there. Proper material selection, design, application, and detailing to accommodate movement are essential in achieving suitable performance. Liquid-applied silicone membrane systems are one of the few roof products that have been successfully used in the Guam environment. After construction of a 170 000 square foot retail center, structural cracking of the concrete roof decking created cohesive tears of the fluid-applied roof membrane that led to water leakage. The investigation, testing, and development of repair details associated with the silicone system to address the roof membrane are discussed. The investigation to determine the cause of the membrane failures identified cracks that formed along girder lines in the concrete decking. The fluid-applied membrane placed directly on the concrete was unable to accommodate the crack displacement and dynamic movement, resulting in tearing of the membrane. Inadequate concrete reinforcement and an absence of control joints or concrete crack treatment prior to membrane placement contributed to the membrane tearing. Details involving sealant joint design in combination with locally reinforced fluid-applied membrane were developed and tested to repair the roof deck membrane. During development of repairs, various joint profiles, sealant backings, and material combinations were tested to determine their ability to accommodate movement. Repairs included routing existing cracks to create a sealant profile able to accommodate anticipated movement and provide redundant water seal should the membrane leak. Further refinements of the final repair configuration were added during repair implementation to accommodate installation difficulties with the harsh environment.