Originally invented in the 1970s, the first industrial sized Cross-Laminated Timber (CLT) manufacturing
facilities were established in Europe in the late 1980s and are increasingly gaining recognition as a high-performance material for structural systems.
Now, there are half a dozen major producers, located mainly in Austria, Germany and Scandinavian countries. This emerging successful system from Europe has been identified by the forest products industry and the research and wood design communities in Canada as a new opportunity for wood in non-traditional applications. CLT is now available in Canada.
Cross-Laminated Timbers (CLT) are large engineered wood panels manufactured by cross laminating lumber with adhesives or fasteners. CLT is produced with three to seven layers of lumber or planks stacked on one another at right angles and are either glued together in a hydraulic or vacuum press over their entire surface area or nailed together. Each layer is composed of softwood boards. Panel thickness is usually in the range of 50 mm to 300 mm but panels as thick as 500 mm can be produced.
Panel size ranges from 1.2 to 3 m in width and 5 to 15 m in length. Openings within panels can be pre-cut in the factory to any dimension and shape, including openings for doors, windows, stairs, service channels and ducts. The resulting product is loadbearing, stable and can act as a diaphragm or shearwall.
Because of CLT’s structural properties and dimensional stability the product is well suited to floors, walls and roofs used in mid-rise construction. The walls and floor panels may be left exposed in the interior which provides additional aesthetic attributes. The panels are used as prefabricated building components which can speed up construction practices or allow for off-site construction in remote locations.
“In Canada, CLT is gradually becoming a popular material in the construction of multi-storey structures, i.e. buildings with four or more floors,” explained Richard Desjardins, Manager, Building Systems, at FPInnovations.
CLT has gained traction since 2000 in the emerging green building movement. Engineered wood products offer a strong combination of environmental performance and sustainability, design flexibility, cost-competitiveness and structural integrity.
Introducing CLT to North America
YouTube video:Introducing Cross-Laminated Timber (CLT)
Video appears courtesy of naturally:wood.
In 2010, the North American wood industry was implementing a plan to introduce generic CLT products in Canada and the United States including:
- Developing quality assurance procedures for the manufacturing of CLT,and
- Developing design values and design procedures for CLT panels that could be adopted by wood design standards and building codes.
To facilitate the introduction of CLT in North America research was being conducted to address:
- Mechanical properties of CLT using North American wood products,
- The type of connections systems to use for CLT panels in various applications,
- Design methodology to address floor vibration,
- Fire performance of CLT panels,
- Acoustical performance of CLT assemblies, and
- Seismic performance of structures utilizing CLT construction.
In October 2007, a 7-storey full-scale CLT building was tested in Japan on the largest shake table in the world. The test simulated the 1995 Kobe earthquake which had a magnitude of 7.2 and accelerations of 0.8 to 1.2g. There was no residual deformation at the end of the test. The maximum inter-storey drift was 40 mm (1.3%) and the maximum lateral deformation at the top of the structure was 287 mm.