Practical solutions are needed for on-site moisture management of mass timber construction. Six groups of cross-laminated timber (CLT) specimens, together with reference specimens including plywood, OSB, and nail-laminated timber were assessed for their wetting and drying behaviour. The focus of this study was to assess the effectiveness of water repellents and membranes installed on CLT in preventing the wetting that can be caused by, for example, rain during outdoor exposure, installation of wet concrete topping, or sitting on a damp concrete slab. Seven water repellent products covering a range of formulations and three membranes including a self-adhered vapour-permeable membrane, a self-adhered vapour-impermeable membrane, and a lumber wrap were assessed as potential temporary moisture protection measures. Implications for moisture protection practices based on the test were summarized at the end of this report.
Project contact is Jean-François Lalonde at Université Laval
Mobile digital tools (tablets and mobile phones) are ubiquitous in our lives. The potential of the cameras of these tools is under-exploited if we consider the geo-spatial information that they can provide to the information management systems (BIM) via cloud platforms for example. The images captured by these cameras can be combined with information from other sensors (gyroscope, accelerometers, etc.) and thus aligned with a BIM model. Many of these technologies are commonly used for robotic localization. The project would aim to assess whether current technologies could be used to track construction progress and identify non-conformities. The project would also determine the level of precision that can be achieved.
The two primary considerations for construction project management are budget and time management. Modular construction has the potential to improve construction productivity by minimizing time and costs while improving safety and quality. Cross-Laminated Timber (CLT) panels are beneficial for modular construction due to the high level of prefabrication, adequate dimensional stability, and good mechanical performance that they provide. Accordingly, CLT modular construction can be a feasible way to speed up the construction and provide affordable housing. However, an in-depth study is needed to streamline the logistics of CLT modular construction supply chain management. CLT modular construction can be performed by two primary means based on type of modules produced: panelized (2D) and volumetric (3D). This research aims to help the Architecture, Engineering, and Construction (AEC) industry by developing a tool to assess the impact of various logistical factors on both panelized and volumetric modular construction productivity. Discrete-Event Simulation (DES) models were developed for panelized and volumetric CLT modular construction based on a hypothetical case study and using data collected from superintendents and project managers. Sensitivity analysis is conducted using the developed models to explore the impact of selected manufacturing and logistical parameters on overall construction efficiency. Comparing volumetric and panelized simulations with the same number of off-site crews revealed that the volumetric model has lower on-site process duration while the off-site process is significantly longer. Accordingly, from manufacturing to the final module assembly, the total time for the volumetric model is longer than panelized model. Moreover, the simulations showed that volumetric modular construction is associated with less personnel cost since the main process is performed off-site, which has lower labor costs and a smaller number of crews required on-site. This framework could be used to identify the optimum construction process for reducing the time and cost of the project and aid in decision-making regarding the scale of modularity to be employed for project.
Traditionally, mid-rise buildings, typically 6-12 stories in height, have used concrete and steel as
structural materials. Recent advancements in engineered wood products, as well as increased concerns for environmental impacts, such as carbon emissions, are driving interest in utilizing mass timber as the primary structural system for mid-rise buildings, particularly residential projects in British Columbia. Demonstration projects like UBC Brock Commons Tallwood Building have showcased the feasibility and opportunities of mass timber structural systems, and anticipated changes to the national and provincial building codes could facilitate the development of mass timber buildings up to twelve stories in the near future.
The City of Vancouver is the regulating body for the building construction in Vancouver and as such, is developing policies that could incorporate considerations for building mid-rise mass timber buildings. While there has been a significant amount of well-documented research on the characteristics and performance of mass timber products and structural systems, there has been less on the cost implications and affordability factors of mass timber buildings above six stories. Cost is a major driver and constraint for decisions at every stage of building projects, from planning through operations, and the lack of information is an area of uncertainty in the widespread adoption of mass timber as a primary building construction material.
This study, Literature review of cost information on mid-rise, mass-timber building projects, was initiated by the City of Vancouver’s Sustainability Department, and was undertaken in the summer of 2019 by the University of British Columbia’s Sustainability Initiative. The study aims to develop an understanding of various cost indicators and the data available in the literature to identify evidential support for the benefits of mass timber construction. The results may inform the City of Vancouver on the current trends, knowledge gaps and future research identified in the literature, and serve as a starting point in collecting cost relevant information for policy and regulations.