Variability of in-situ testing in wall coating systems - Karsten tube and moisture meter techniques

Abstract

To meet customers' demand and adequate levels of satisfaction, there are various reasons for the need of proactive maintenance and knowledge about in-service performance of building façades. From this perspective, performing inspections depends on the in-service appraisal's reliability and the presence of monitored and measured parameters along the life cycle under real exposure conditions. Water, the major in-service deterioration agent, has different origins and transport mechanisms through façades, including wind-driven rain, ground moisture, and wetting/drying of surfaces, resulting in various chemical and/or physical-pathological phenomena. Thus, water resistance is considered highly relevant due to its significant influence on the durability of coating systems. This study presents results of an investigation concerning the water resistance of in-service wall coating systems, focusing on conventional and industrial renders and adapting appropriate techniques for field analyses, namely Karsten tube and moisture meter. In-service parameters (water absorption under low pressure and surface moisture) are assessed, and the techniques' sensitivity is analysed considering exposure and inspection conditions, roughness, coating and finishing types, and existing anomalies. The capacity of these techniques to monitor in-service performance is also discussed, and in-service performance criteria are proposed.