Assessing Water Loads Post-Flooding in Envelope Assemblies: Effects of Interstices and Hydrostatic Pressure

Recurring floods and increasing disaster management costs highlight the need for resilient building envelope assemblies, and this also applies to Québec, Canada. This study investigates the effects of hydrostatic pressure and interstitial gaps between materials on water loads, and drying behaviour on the occurrence of damage (e.g., swelling, mould growth) in building assemblies. Based on flood event scenarios, individual envelope components were exposed to varying water levels and durations to document the effect of hydrostatic pressure. Neutron imaging was employed to visualize water drainage and residual water trapped within interstices. Additionally, a dedicated experimental setup with 80 thermocouples and 20 probes was utilized under controlled conditions to monitor drying processes in representative assemblies. We found a 2 m hydrostatic pressure led to a significant increase in water uptake, e.g., 20% for spruce under water for 4 days. In addition, interstitial gaps act as reservoirs and preferential water pathways. In consequence, this added water notably delays drying and heightens mould risk. The combined dataset from these experiments will improve our understanding of assemblies’ behaviour during flood events and inform flood-resilient design guidelines.