Moisture monitoring of mass timber building - study of condition variation and building environment design

Abstract

Exposure to moisture can occur either during building construction (heavy rain/flash flooding) or in-service (condensation/plumbing leaks). Mass timber products such as cross-laminated timber (CLT) have higher capacity to absorb and store moisture than other timber products. Prolonged moisture exposure can lead to decay, necessitating drying, repairs or replacement of building sections. It is crucial to incorporate moisture management/safety into building design and construction planning to prevent any moisture complications. To study the environmental condition of mass timber construction in hot and humid climates, wireless moisture monitoring sensors were installed in a mass timber building under construction in tropical Queensland. The project studied condition variations within the building layer up, exposed to indoor and outdoor micro-climates. MC data collected were used to simulate mould growth index (MGI) predictions and evaluate the panel condition after construction was completed and in correlation with building design, preventative measure applied and environmental factors. Comparative analysis showed that MC values dropped to acceptable levels after temporary exposure to moisture. Various preventive measures such as design with protection, roof installation as early as possible and application of weather resistant membranes (WRM) on the external face of the CLT wall panels were effective to keep moisture elevation minimal. Hygrothermal modelling showed that the model can predict MC in the range tested; however, further studies are required to examine the model accuracy in higher MC ranges. The MGI calculations for monitored locations showed slight elevation when there was moisture exposure. Further studies are recommended to determine MGI using external environmental values for the sections of CLT exposed to outdoor environment.