Seyedmohammad Kahangi Shahreza

Inappropriate bricklaying techniques can result in extruded mortar joints, which may partially fill the air gaps within brick veneer timber frame walls. This leads to an unintended connection or “bridge” between the brick masonry cladding and its adjacent layer (such as insulation or weather-resistant barriers). This bridging effect compromises the capillary break function of the air gap, allowing water to reach adjacent layers and intensifying the impact of water penetration, under wind-driven rain (WDR) conditions. This study employs a probabilistic analysis in combination with a machine learning metamodel to investigate the impact of extruded mortar joints on mould growth. The metamodel, developed using the random forests (RF) machine learning algorithm, is used to predict the maximum mould index (MMI). In addition, this study assesses the effects of two different water penetration criteria—ASHRAE and experimental study-based (ES)—on extruded mortar joints under climatic conditions in Gothenburg, Sweden. In order to figure out how different orientations affect the analysis; the study examines the case study from four different orientations. The findings showed that the ES and ASHRAE criteria were in agreement for orientations with substantial WDR loads (e.g. south). On the other hand, the ASHRAE criteria illustrated a higher MMI than the ES criteria in walls facing orientations with relatively small WDR loads (e.g. north). Furthermore, an increased extruded mortar depth and higher MMI were shown to be positively correlated by the linear and non-linear mould sensitivity analyses. However, depending on the WDR loads (or different orientations) and chosen water penetration criteria, this correlation’s strength can vary. The air change rate (negative correlation), the solar absorption coefficient (negative correlation), the WDR’s reduction/splash coefficient (positive correlation), and the thermal conductivity of the Rockwool insulation (positive correlation) were additional important variables influencing the MMI.

This study investigates the impact of brick types and workmanship on water penetration in brick masonry veneer walls. Masonry specimens, built by two masons using solid and perforated bricks with two different laying methods, were subjected to an average water spray rate of 28 l/m²·h. Results indicate that, on average, the water penetration rate was approximately twice as high in solid bricks as in perforated bricks. The workmanship could significantly influence the penetration rate in solid bricks, with rates varying up to eightfold depending on the mason's skill and technique. However, workmanship variations had negligible effects on penetration rates for perforated bricks. These findings emphasize the significance of workmanship, particularly in the case of solid bricks, in ensuring the hygrothermal performance and durability of masonry walls.

The present paper investigates the impact of different water penetration criteria on the risk for damage in a common type of building envelope in Nordic countries, timber frame walls with brick masonry veneer. The studied walls are evaluated based on one damage criterion, the risk of mold growth. The study investigates several parameters: water penetration criterion, type of moisture source (uniformly distributed or point source) and its position in the wall assembly, air change rate (ACR) (representing different workmanship scenarios), wind-driven rain (WDR) coefficient, and locations (Gothenburg and Rensjön, with different average annual rainfall and temperature). Two criteria on how to implement water penetration are compared: a) a commonly accepted reference model that assumes one percent of all wind-driven rain deposited on the façade to penetrate the clay brick cladding, and b) a new criterion stating that 3.8% of WDR penetrates when the water content of the brick veneer cladding is above 90% of its saturation capacity. The simulation is done for a thirteen-year period with WUFI Pro and WUFI 2D. The results indicate the greater importance of implementing water penetration compared to ventilation in cavities. Further, the findings suggest that the moisture source’s location significantly impacts the mold growth risk. The results also show that the choice of the WDR coefficient affects the risks, which suggests that this factor needs accurate quantification for hygrothermal analyses. The results in this study suggest that an effective measure for the design/maintenance of such walls should incorporate: a) limiting the amount of water penetrating through the cladding, particularly stopping water from reaching the sensitive elements, i.e., timber studs, b) removing extruded mortar stemming from poor workmanship, if any, which may act as a capillary bridge.