CLT is an engineered wood panel product made from layers of lumber glued together in alternating directions. Due to the perpendicular orientation of each layer, CLT is dimensionally stable and very rigid, allowing it to be used as floor slabs, load-bearing walls, and shear walls in mid- and high-rise construction. The boards in a CLT panel are glued together using a large hydraulic press. CLT is produced in a range of thicknesses and panel sizes. The most common panel types are three-ply, five-ply, and seven-ply. Panels are typically 10' wide and can be produced in lengths exceeding 40'. CLT technology originally developed in Europe during the 1990s, and in recent years its popularity in the US continues to grow.
What are the advantages of using CLT and other wood products in construction?
Sustainability. Wood building products are derived from a natural and renewable source. Trees remove carbon from the air as they grow and store it in a process known as carbon sequestration. That carbon remains stored when wood is transformed into a building material. Carbon sequestration, coupled with the fact that wood products generally require less energy to produce than other conventional materials, results in significant environmental benefit. For the Framework project, preliminary calculations show probable embodied carbon savings in the structure alone of over 60-percent compared to a conventional structure. When harvested from forests with appropriate management practices in place, the use of CLT does not contribute to deforestation. The possibility of creating CLT from smaller pieces of lumber mean that it can be made from smaller, lower grade timber.
Rural Economic Growth. Wood buildings connect urban development with rural economic growth. Greater demand in the US for CLT and other engineered wood products has the potential to substantially increase forestry and timber-related manufacturing jobs in rural communities.
Pre-Fabrication. Mass timber buildings like Albina Yard and Framework are made from engineered wood columns, beams, and panels that are pre-cut and pre-fabricated off site. Analogous to the assembly of flat-packed prefabricated furniture, these components are brought to a construction site pre-organized for quick installation. During the construction of Albina Yard, the first 4,000 sf of CLT flooring panels were installed in less than four hours. This would have taken a week or more using traditional construction methods.
Lightweight. CLT has a high strength to weight ratio, making it lighter than many conventional materials but structurally as strong. The comparative lightweight nature of timber structures can reduce the cost of foundation work and mean that delivery to construction sites is less expensive than comparable structural elements.
Architectural Beauty and Well-Being. Working with CLT allows us to create new kinds of architectural experiences. Exposed wood is beautiful, and the emerging awareness of biophilic design suggests that using visible natural materials in buildings has a positive impact on building inhabitant’s psychological well-being, productivity, and speed of learning.