What is Cross-Laminated Timber?
Cross-Laminated Timber is an engineered wood panel generally made of three, five, or seven layers of dimension lumber oriented at right angles to each other and glued to create structural panels with exceptional strength, dimensional stability, and rigidity. CLT is a flexible building system, because the panels are factory prefabricated to the size specified by the design. This building system originated in Austria more than two decades ago, and spread across Europe, but has not become established in North America.
Is Cross-Laminated Timber available in North America?
CLT is currently imported into North America from Quebec, British Columbia, and Europe. The available dimensions are up to 19-1/2 inches thick, 18 feet wide, and 98 feet long.
Is Cross-Laminated Timber expensive?
When you consider the total in-place value of a cross-laminated timber system, it is cost competitive to other pane construction materials. Other things to consider are the value added benefits such as, a reduction in installation costs, which is normally 50% cheaper than installing other plate materials. Using CLT is also much more time efficient, and can push up the completion date sometimes months ahead of schedule. A CLT system also weighs less than traditional building systems, thus reducing foundation costs.
Does Cross-Laminated Timber meet building codes?
Currently codes are shifting to facilitate new technology that, in turn, is permitting wood structures of sizes and heights, that were unthinkable in the past. With the inception of the International Building Code, commercial structures built of wood frames have been able to increase to larger building sizes, allowed by the upper limits of each of the legacy building codes. Although certain uses and occupies still retain traditional size restrictions, limits for many low-rise buildings are nearly gone.
What are some advantages of CLT Paneling?
Cross-Laminated Timber contains fewer concealed voids, as well as a char layer that provides fire resistance, its dimensional stability and rigidity also provide earthquake resistance. CLT paneling’s “in plane and out-of-plane strength and stiffness properties, and two-way action capabilities are similar to a reinforced concrete slab.” (Karacabeyli, E. (2013). Introduction. CLT handbook: cross-laminated timber (U.S. ed., ). Pointe-Claire, Quebec Canada: FP Innovations.)
CLT paneling is also thermally efficient, requiring 1/3 the heating and cooling energy compared to other traditional building systems. CLT paneling is also beneficial to the environment. Wood is the only major building material that grows naturally and is renewable, CLT also outperforms steel and concrete in terms of embodied energy required to make the product. It also has a less of an effect on air pollution (stores carbon) and water pollution.
How is Cross-Laminated Timber manufactured?
The typical manufacturing process of this product involves the following steps. 1. The selection of quality lumber, 2. lumber grouping and planing, 3. application of adhesives, 4. panel lay-up and pressing, 5. product cutting and surface machining, 6. marking and packaging.
A successful manufacturing process is dependent upon the consistency of lumber quality and control of the variables that effect the quality of the bond of adhesives. Many procedures are implemented to insure the quality of the product. The lumber is generally kiln dried to an approximate moisture content of 12%. This drying prevents potential changes in the dimensional structure of the panel as well as cracking in the surface layers.
What types of adhesives are used in CLT Panels?
The adhesives used for CLT panels must meet the same requirements as the ones used in glued laminated timber manufacturing. These adhesives include qualified polyurethane, melamine and phenolics.
Does CLT adversely affect indoor air quality?
Regulatory and non-governmental organizations that address indoor air quality issues, generally focus on volatile organic compounds (VOCs) which also includes formaldehyde, due to its inclusion in adhesives. VOCs and formaldehyde are reported as key factors that relate to the discomfort of people working and living inside buildings. Five CLT products (differing thicknesses, and number of glue lines) were evaluated for their indoor emissions of VOCs. This research concluded that CLT products have a very low or even a zero impact on indoor air quality. (Karacabeyli, E. (2013). Introduction. CLT handbook: cross-laminated timber (U.S. ed., )
Are there enough forest to sustainably support CLT manufacturing?
Since the increase in usage of CLT products, the question of timber shortage has risen, due to CLT’s potential to increase the volume of wood used for construction. While the use of CLT products could increase the volume of timber used, there are strict forest management policies and practices that restrict the amount of timber harvested in North America. These practices ensure the sustainable regeneration of North American forest, so that harvesting levels never surpass regeneration levels.