Novel water penetration criterion for clay brick masonry claddings

Despite the impact of water penetration on the performance of building envelopes, no general agreement is available on implementing water penetration due to wind-driven rain (WDR) in hygrothermal and moisture safety analyses. This study proposes a novel criterion for water penetration in clay brick masonry that depends on the water content level of masonry. An experimental campaign investigating water penetration in clay brick masonry exposed to uniform water spray is conducted on masonry triplets prepared from bricks with different water absorption properties and three mortar joint profiles. During each test, water absorption and water penetration are registered continuously. The results show that no water penetration occurs unless the water content of the specimens is above 90% of their saturation capacity. The saturation level at which penetration starts is consistent across all joint profiles and brick types. Accordingly, exposure to driving rain at levels below the threshold may not lead to water penetration. The utility and implications of the proposed criterion are briefly demonstrated by analyzing water content and water penetration in a clay brick masonry façade. The resulting water penetration is compared with the results obtained using a commonly accepted reference model that assumes one percent of all wind-driven rain deposited on the façade to penetrate the clay brick cladding. By linking water penetration in clay brick masonry to the water content, the proposed criterion is an attempt to logically explain a phenomenon of high scientific and practical relevance for moisture analyses of a frequently used type of building envelope.