Barriers to the design and use of cross-laminated timber structures in high-rise multi-family housing in the United States

Wood structures not only have a significantly lower embodied energy and associated carbon emissions than equivalent steel and concrete structural systems, wood is a carbon sink, removing carbon dioxide from the atmosphere and storing it in building components. The reduction of carbon dioxide is critical to addressing related energy and climate issues. Unfortunately, the structural properties and life-safety concerns have limited the use of wood to the structural systems to low-rise buildings in the United States. This paper uses the hypothetical design of a high-rise multi-family housing building using Cross-Laminated Timber (CLT) to address these barriers and highlight the potential of CLT for use in the United States. CLT adapts itself more naturally to multi-family housing than other building typologies due to the solid panel nature and limitation in spans. It has been chosen to use a high-rise design since there are stricter building codes and to understand if professionals feel CLT is capable to reach high-rise limits safely. Since post-tensioned concrete is the typical structural system currently for high-rise multi-family housing, CLT will be compared to this system. CLT is an engineered wood product consisting of glue laminated wood boards, approximately 20-60mm in thickness, with each layer set at right angles to the next layer. This cross lamination creates panels, ranging from a 3-layer 57 mm (2.24 in) panel to as thick as an 11-layer 300 mm (11.8 in) panel, capable of spanning in two directions and being used for load-bearing walls and spans. CLT was first developed in the early 1990s in Austria and Germany and has been gaining popularity in residential and non-residential applications, mainly in Europe. Currently, panels are being manufactured in a limited number of places in North America, which allows CLT to be used in a few projects while trade organizations and governmental agencies adopt specifications and codes for its use. While CLT is being used in Europe as the structural system for eight-story buildings and proposals up to seventeen stories, the barriers to the adoption of CLT for high-rise construction in the United States needs to be exposed and understood. Through the use of semi-structured interviews and surveys of design, engineering and construction professionals, this paper analyzes these barriers that include systems integration (fire-safety, acoustics, plumbing, electrical), aesthetics and information gaps.