The objective of the current project is to develop a performance-based design process for wood-based design systems that would meet the objectives and functional statements set forth in the National Building Code of Canada. More specifically, this report discusses the fire and seismic performance of buildings, as identified as a priority in a previous FPInnovations report (Dagenais, C. (2016). Development of Performance Criteria for Wood-Based Building Systems).
Model building codes in the United States limit timber construction to six stories, due to concerns over fire safety and structural performance. With new timber technologies, tall timber buildings are now being planned for construction. The process for building approval for a building constructed above the code height limits with a timber load-bearing structure...
Canadian Conference on Building Science and Technology
Cross laminated timber (CLT) and mass timber construction is a promising structural technology that harnesses the advantageous structural properties of wood combined with renewability and carbon sequestering capacities not readily found in other major structural materials. However, as an organic material, mass timber is susceptible to biodeterioration, and when considered in conjunction with increased use of engineered wood materials, particularly in more extreme environments and exposures, it requires careful assessments to ensure long-term performance.
A promising approach towards reducing construction moisture in CLT and other mass timber assemblies is to protect the surfaces with a water-resistant coating. To assess this approach, a calibrated hygrothermal model was developed with small and large scale CLT samples, instrumented with moisture content sensors at different depths, and treated with different types of water resistant coatings exposed to the Vancouver climate. The models were further validated with additional moisture content sensors installed in a mock-up floor structure of an actual CLT building under construction. Biodeterioration studies assessing fungal colonization were undertaken using the modified VTT growth method and a Dose-Response model for decay potential.
The research indicates that CLT and mass timber is susceptible to dangerously high moisture contents, particularly when exposed to liquid water in horizontal applications. However, a non-porous, vapour impermeable coating, when applied on dry CLT, appears to significantly reduce the moisture load and effectively eliminate the risk of biodeterioration. This work strongly suggests that future use of CLT consider applications of a protective water-resistant coating at the manufacturing plant to resist construction moisture. The fungal study also highlights the need for a limit state design for biodeterioration to countenance variance between predicted and observed conditions.
The report describes a new structural system in wood that is the first significant challenger to concrete and steel structures since their inception in tall building design more than a century ago. The introduction of these ideas is fundamentally driven by the need to find safe, carbon-neutral and sustainable alternatives to the incumbent structural materials of the urban world. The market for these ideas is quite simply enormous. The proposed solutions have significant capacity to revolutionize the building industry to address the major challenges of climate change, urbanization, sustainable development and world housing needs.