The idea of mass-timber construction as a building typology gained some traction in the U.S. during the last two years, thanks to separate reports by Canadian architect Michael Green, AIA, and SOM that examined the use of wood as a structural material in tall buildings. Now, a survey to be released next month from The Forestry Innovation Investment and the Binational Softwood Lumber Council and carried out by Perkins+Will add to the dialogue with a collection of lessons-learned from the construction of 10 commercial and residential wood buildings from 2008 to 2013 in Europe and Canada, where regulatory environments are generally favorable to innovation in materials and their applications.
Unsurprisingly, the survey—which was provided to EcoBuilding Pulse in advance of its public release—endorses the use of wood in tall-building construction. It also acknowledges aspects of the emerging construction practice that still need ironing out before mass-timber can be implemented more broadly, particularly in the U.S. Among them: a lack of uniformity in construction solutions that deal with issues such as durability, fire-protection, and acoustics, as well as inconsistencies in regulatory approval processes from one project to the next.
The report incorporates written and verbal feedback from more than 50 stakeholders, representing each project’s developer and owner, design team, construction team, and jurisdictional authorities.
Members of the design teams interviewed for the survey include project architects, structural engineers, timber-product fabricators, and academic research partners. Collectively, they cited the desire to be seen as innovative and to improve a building’s energy performance as the primary motivators for using structural wood technology, and most had planned to use the material from the design’s conception. According to the report: “Project teams emphasized the need to approach the work as wholly innovative, rather than focusing innovation on wood only.”
Prefabricated wood components were common among the projects and key, design team members said, to delivering the project on time and without major disruptions to the jobsite. For example, when developing Swiss media group Tamedia’s headquarters in Zurich (shown, above), designed by Shigeru Ban Architects and completed in July 2013, the design team reported that 80 percent of the building was designed and detailed for prefabrication. A post-and-beam structure was used to achieve the wide spans and re-configurable, open floor plan.
Additionally, members of the design teams surveyed said that research partnerships were vital to finding innovative and efficient design solutions. German studios Atelier PK, Roedig Schoop Architekten, and Rozynski_Sturm Architekten collaborated with the Technical University of Braunschweig in Germany on the design of 3XGRÜN (shown, below), a five-story, 13-unit multifamily project in Berlin. The structure uses laminated veneer lumber beams, glulam columns, and cross-laminated timber floors. It was designed as a prototype of a prefabricated timber structure through a local research collaboration (here and here) that aims to engage design teams with mass-timber construction.
Survey respondents reported that fire protection was a concern, particularly in wood-clad projects such as Holz8, an eight-story multifamily project in Bad Aibling, Germany. However, Schaunkula Architekten in Munich collaborated with Germany-based research institutions including the Technical University of Munich and the Rosenheim University of Applied Sciences to research exterior finishes and envelope design that would allow the building to keep its wood aesthetic while helping it meet fire codes, such as metal flashing between each floor to help stop the spread of fire.
Other lessons learned include:
- Teams should allow more time for the design-development phase in order to weigh options and incorporate additional costs into the initial budget.
- Projects in regions whose governing policies support low-carbon materials allowed for more rapid development of mass-timber construction.
- Architectural and structural designers surveyed said they experienced up to a 50 percent increase in design time compared to a concrete structure, and most of that time was spent detailing interfaces between materials.