Utilization of low-grade timber in the construction industry

This study explored the adaptation of the Australian sawn timber industry to evolving market demands, climate change impacts, and variations in harvested wood characteristics. It was driven by a key challenge: the growing misalignment between the increasing demand for high-stiffness timber products and the industry's diminishing ability to supply them, largely due to declining fibre quality from intensively managed plantations. The study aimed to optimize the use of Australian timber resources by reviewing the supply chain of sawn timber products and identifying areas where technological enhancements, process improvements, or new product developments could be initiated. A critical review revealed broad consideration of opportunities for minimising or utilising low-grade timber across the supply chain is currently missing from the literature. The methodology adopted in this study was a combination of literature review, survey and interviews, site visits, and structural modelling. Specifically, the study incorporated detailed structural modelling of representative single-storey and double-storey residential buildings using out-of-grade timber, simulating variable material stiffness and applying probabilistic methods in accordance with AS1720 and ISO 2394 to evaluate structural reliability. In addition to the comprehensive industry review, this study introduces building-scale structural modelling using out-of-grade timber and probabilistic strength comparison against AS1720 and ISO 2394 benchmarks. This engineering-based analysis reveals feasible pathways for the certified use of low-grade timber in residential construction. The research highlighted significant opportunities for employing low-grade timber in residential building construction through an analysis of the mechanical properties of the timber along with building-scale modelling of the structural performance, thereby promoting more comprehensive utilization of the tree. This approach not only adds value to the built environment but also aligns with global efforts to reduce greenhouse gas emissions and enhance profitability across the entire supply chain, from timber growers to end-users. The key findings of this study were that improved data sharing between growers and sawmills could increase fibre quality, custom structural products exist to utilise low-grade timber, existing post-processing technologies can be leveraged to upgrade low-grade timber, out-of-grade timber can be viable in certain residential scenarios, and there is a reluctance in industry to using low-grade timber. Key future initiatives include leveraging findings from previous studies to extend their application into built environments, addressing the mechanical properties shortcomings of materials through innovative technologies, and refining structural design and construction of low-grade timber buildings with advanced modeling. These efforts aim to develop cost-effective, sustainable, and marketable structural solutions for enhancing the viability and environmental footprint of the timber construction industry.