Cross Laminated Timber (CLT) is an extremely strong engineered wood panel intended for roof, floor, or wall applications. Currently there is little research comparing CLT to steel and concrete, materials CLT hopes to replace This research uses a detailed literary analysis on CLT and case study on Carbon12, a recently constructed CLT structure in Portland, Oregon, to compare the cost and schedule requirements of CLT with a cast-in-place concrete slab. The case study consisted of a detailed analysis of Carbon12, interview with Scott Noble, senior project manager for Carbon12, and a detailed schedule and cost analysis. Results showed that for a concrete floor system used on Carbon12, material costs were far less than costs for a CLT floor system and labor costs were far greater than costs for a CLT floor system. For the schedule analysis, results showed that a concrete floor system would add an additional 10 weeks to the construction schedule of Carbon12. These results led to the conclusion that CLT is a feasible building material for dense, urban, mid-rise structures similar to Carbon12. The quick installation time, small crew, and environmental benefits of CLT outweigh the added costs of the material.
This project developed Cost Plans for the structure of four building types; a 7 storey office building, an 8 storey apartment building, a 2 storey aged care facility and a single storey industrial shed. Each solution was designed and then independently costed for a timber option as well as a more conventional concrete framed or steel framed solution for a reference location in suburban Sydney. The site was assumed to have no significant cost implications concerning site access, ground conditions or neighbouring properties. The investigations considered only the elements of the building for which there were significant difference and ignored the cost of elements that were the same.
The timber structural solutions were found in all cases to be significantly less than the competing non-timber solution. The cost of each of the main components were found to be significantly cheaper in timber for each building.
The next best opportunity for the timber industry is the office and institutional building markets as both building forms are similar. This report shows that this market segment has great potential as this building design showed the significant cost savings particularly if a decorative ceiling is omitted.
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.