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2020 marked the beginning of a new decade, and the timber construction industry ushered in even greater development opportunities. With the continuous optimization of timber construction technology, Canadian standards now allow the construction of high-rise timber buildings up to 12 stories, up from the previous limit of 6 stories. With British Columbia's approval last year to adopt the new regulations, all provinces are now permitted to construct even taller heavy timber buildings. In fact, prior to this, the number of large-scale timber construction projects had already shown a gradual upward trend. For example, the 18-story Brock Commons student residence at the University of British Columbia was a prime example of this trend. Furthermore, the Sidewalk Labs project in Toronto is planning to build a community using timber structures, including a planned 30-story timber building. All of this indicates that the development and popularity of timber construction are moving in a more profound direction.
All of this is made possible by breakthroughs in the form of timber as a building material. Heavy timber structures extensively utilize engineered wood, such as glued laminated timber (Glulam), cross-laminated timber (CLT), and nip-jointed timber (NLT), as the main load-bearing structural materials, and have performed admirably. With the increasing awareness of fire safety in buildings and the growing market recognition of the fire-resistant properties of engineered wood, people no longer perceive heavy timber structures as having a higher potential fire hazard. Furthermore, the environmental and economic benefits of timber as a building material are becoming increasingly apparent. As a natural resource, it is readily available and renewable. Moreover, its carbon footprint is shorter than other building materials, such as steel or concrete, in obtaining and transporting it. In other words, obtaining steel and concrete requires burning more fossil fuels and emitting more carbon dioxide. From a cost perspective, significant savings can be achieved during construction due to higher construction efficiency. The engineered wood components used in heavy timber structures are prefabricated in factories and flexibly installed on-site as the project progresses. At the same time, these components are much lighter than those using steel or concrete, reducing the difficulty of on-site hoisting and installation. All of the above combined means that these buildings can be constructed faster, more efficiently, and at a lower cost. For example, the Brock Commons student residence at the University of British Columbia took only 70 days from prefabricated components to complete assembly.
Despite the advantages mentioned above, heavy timber structures have indeed faced unique challenges in sound insulation and noise reduction. Because heavy timber structures are lighter than concrete structures, they are less likely to block sound transmission, making it easier for lower frequency sounds to penetrate walls.
With technological breakthroughs, we can now reduce sound transmission within buildings through sound insulation and noise reduction designs, enabling heavy timber structures to achieve the same level of sound privacy as reinforced/concrete structures. Below are some of these designs and methods that we will share with you today.
1. Reduce sound transmission paths around the wall.
In timber-framed buildings, sound travels relatively easily through various pathways, including floors, ceilings, grilles, cavities, ducts, and the junctions between floors and walls. These pathways can even be the primary channels for noise transmission compared to walls themselves. Therefore, the construction of partitions is essential. For example, to prevent sound from entering the floor and then spreading to other rooms, partitions are necessary, as are those for ceilings. These partitions must be considered in the initial design and allocated sufficient space.
2. Choose more suitable engineered wood products
In heavy timber construction, there are many types of timber components to choose from, such as glued laminated timber (Glulam), cross-laminated timber (CLT), and nail-jointed laminated timber (NLT). Different types of components are suitable for different applications. For example, acoustic tests have shown that CLT performs better in terms of sound insulation because it is made of cross-oriented planks laminated together. Therefore, it is more suitable for use in interior walls and floor slabs.
3. Increase the amount of wood used in glued laminated timber.
More layers of glued laminated timber (CTL) provide better sound insulation, sometimes even achieving the same effect as steel/concrete structures. It is recommended to use CTL products with at least 5 or more layers.
4. Use in combination with other materials
Combining wood with other heavier materials, such as concrete, can effectively reduce noise. This is achieved by pouring a 1-3 inch thick layer of concrete or plaster on top of the wood-based components. Placing a soft rubber or semi-rigid insulation material between the wood structure and the concrete further enhances noise reduction.
The methods described above can help us address the challenges posed by noise transmission to heavy timber structures. However, the key to using these methods is that they need to be considered during the project design phase to avoid post-construction remediation, such as demolishing walls, floors, or ceilings for renovations, which would add extra costs to the project.