Mass Timber and Wood Framing
New and traditional approaches reduce cost and meet code for mid-rise construction
Use the following learning objectives to focus your study while reading this month’s Continuing Education article.
Learning Objectives - After reading this article, you will be able to:
- Discuss the ways in which wood contributes as a structural building material in mid-rise construction.
- Distinguish between platform, balloon, and semi-balloon framing.
- Explain the potential of modern mass timber systems.
- Cite examples of various approaches to wood-frame mid-rise construction.
Credits: 1.00 HSW
Mid-rise construction is becoming increasingly popular as a means of boosting densification, containing urban sprawl, and respecting infrastructure limits while maintaining neighborhood charm and community appeal. Multi-family construction in particular has grown, increasing 46 percent between 2009 and 2011. This year, the sector is expected to continue to advance, rising 23 percent over 2011.1
Wood has a key role to play in mid-rise construction. It has proven to be more affordable than concrete or steel, and has a lower environmental footprint than either material. Architects for Stadhaus, a nine-story wood apartment building in England, found that compared to concrete, a wood building offered cost savings of more than 15 percent,2 and that 186 tons of carbon were sequestered within its structure.3
Codes now allow wood as a structural material in five- and six-story wood-frame structures, in most U.S. states and throughout Canada. Traditional wood-frame construction is a proven solution for current mid-rise structures up to six stories, and mass timber is a possible solution for even taller buildings. Both are being used to achieve durable, code-compliant, economical mid-rise developments that add vibrancy at a human scale.
This article will provide a high-level comparative overview of the systems themselves. Wood-frame construction systems including balloon, platform, and semi-balloon framing will be discussed as will mass timber solutions including cross-laminated timber (CLT), glue-laminated timber (glulam), and laminated strand lumber (LSL). Case studies will showcase how architects are using these systems to full advantage either through code-compliant situations for additional stories or by turning to alternative solutionsâ€”methods of construction that are not included in the building code per se, but can be used to meet the intent of codeâ€”to build taller, smarter, and more efficiently with wood.
The University of British Columbia Earth Sciences Building is a five-story wood structure that uses CLT, glulam, and LSL. Architect: Perkins+Will Canada Architects Co.
Photo by K. K. Law