Evaluating the durability of mortise-tenon joints in response to natural moisture weathering over time

When used in the appropriate context, timber structures might have lower embodied carbon than their concrete and steel counterparts, making timber a popular material for sustainable construction practices. To continue constructing with timber we require more in-depth exploration into timber joinery, which dictates the structural stability and performance of timber-framed construction. Moisture can affect the performance of timber joints. Rapid moisture changes over time can lead to joint failure, affecting the structure’s stability and safety. It is therefore important to understand how natural moisture weathering changes affect timber joints to ensure the longevity and safety of structures made from timber. This paper presents and discusses the results of a series of tests conducted by subjecting samples of timber joints to cyclically varying moisture conditions for several cycles and ultimately judging their effect on the performance of timber joints by measuring their rotational stiffness. The experiments select three commonly used timber joint reinforcement methods — traditional mortise and tenon joints, mortise and tenon dowel reinforcement and mortise and tenon glue reinforcement — to represent the majority of timber buildings in the UK. The results were compared to identify the advantages and disadvantages of the three reinforcement methods. The outcomes demonstrate that prolonged exposure to moisture can have a great impact on the performance of timber connections, resulting in decreased stiffness and strength. The use of reinforcement methods, however, such as mortise and tenon dowel reinforcement or mortise and tenon glue reinforcement, can mitigate the negative effects of moisture weathering changes on timber joints. This paper emphasises the importance of understanding moisture weathering changes and their impact on timber joints to ensure the longevity and safety of structures made from timber.