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Timber, once the world's oldest building material, is now experiencing a resurgence. Throughout history, we have continuously explored the structural possibilities of wood, transforming solid wood into more complex and stable modern engineered wood materials through innovations in wood processing technology and engineering techniques. This construction method, currently known in the industry as heavy timber, is shaking the foundations once firmly established in the construction industry with concrete and steel.
Timber is no longer limited to building low-rise buildings. We can now use advanced structural designs and materials to greatly accelerate the construction and processing efficiency of timber buildings, while also allowing timber buildings to be built taller.
As a pioneer in promoting heavy timber construction, Perkins+Will has incorporated heavy timber elements into many of our projects and has worked with industry peers to develop and write numerous technical guidelines, hoping to promote this concept throughout the industry.
Image: Earth Sciences Building at UBC in Vancouver
Image: A prototype curved CLT board being machined on a five-axis CNC machine tool at Autodesk BUILDSpace.
Recently, Perkins+Will collaborated with Fast+Epp, an engineering design firm, to write this NLT (Nail-Laminated Timber Design + Co.) manual.The instruction guide provides a detailed introduction to the design and processing considerations of NLT engineered wood products, as well as some practical case studies.
Image: Some technical manuals written and published by Perkins+Will
What is heavy timber construction?
This is a relatively new concept, basically referring to engineered wood products that use small-sized timber to form larger panel components through gluing, pressurization, and mechanical reinforcement. Unlike traditional light timber structures that mainly use 2x4 or 2x6 timber to form a frame system, this type of structure utilizes panel engineered wood components such as NLT and CLT, and uses specially designed complex metal connectors and precision CNC machining prefabrication to form panel-column or beam-column structures.
1: Wooden buildings are very durable
Our ancestors knew how to build durable wooden structures long ago. From the Yingxian Wooden Pagoda in China to Horyuji Temple in Japan, these wooden buildings, which have stood for thousands of years, have withstood natural disasters such as earthquakes and fires thanks to the special structural designs and protective techniques of the craftsmen of that time.
In North America, although the history of wooden construction is not as long as in Asia, some old wooden buildings constructed in the early 20th century, such as the Landing and Leckie Building in Vancouver and the Backer & Hamilton Building in San Francisco, are well preserved and still in operation.
2: Heavy wood is not just CLT
CLT actually appeared in Europe as early as 1990. Although it is currently the most sought-after engineered wood product, there are many other materials used in the construction of heavy timber structures besides CLT. Many similar engineered wood panel components can partially replace CLT in a more economical way. In addition, there are patented products such as LVL, LSL, and PSL.
Image: Common mass timber products currently on the market
3: Heavy timber structures are more earthquake-resistant.
Heavy timber structures offer superior earthquake resistance compared to traditional concrete structures. This is primarily due to their lighter weight and higher strength-to-weight ratio. The weight of a heavy timber structure is generally only about half that of a concrete building. Furthermore, structural engineers have designed various structural schemes to address the characteristics of different earthquake zones.
4: Heavy timber structures are more energy-efficient
Wood is undoubtedly a natural insulating material. Its thermal conductivity is one-sixteenth to one-eighth that of concrete and one-four-hundredth that of steel. Furthermore, CLT walls, being entirely made of solid wood, and with CLT components typically precision-machined in factories using CNC machine tools, offer superior airtightness and significantly reduce the need for insulation materials. Additionally, CLT uses 3-5 times more wood than lightweight wood structures, resulting in substantial carbon sequestration. Using timber from sustainably managed forests to manufacture heavy timber components can be a powerful tool for mitigating climate change.
5: Heavy timber structures are healthier.
Statistics show that the average person spends 90% of their time indoors. The quality of the indoor environment and air is closely related to human health. Numerous experiments have demonstrated a correlation between exposed wood materials indoors and human stress response indicators. From this perspective, using exposed heavy-duty timber structural components such as glued laminated beams and columns, CLT floor slabs and walls, or wood veneer wall panels can effectively alleviate stress levels for indoor occupants. Furthermore, wood is a natural and environmentally friendly material, greatly benefiting indoor air quality. Another crucial point is that exposed timber components in heavy-duty timber structures serve both structural and aesthetic functions, significantly reducing interior decoration costs.
In summary, based on these five points, as architects, we bear the heavy responsibility of creating sustainable, healthy, and safe buildings for humanity. Heavy timber construction can fundamentally change the paradigm of architecture, providing architects with a completely new approach to selecting sustainable and responsible building materials.