Cross Laminated Timber: Sustainable Building Solutions Explained

The construction industry ranks among the top contributors of carbon emissions, solid waste generation, and raw material consumption globally— thereby mounting pressure on the real estate sector to innovate ways of curbing these. This involves minimizing and offsetting such negative contributions through adoption of more efficient construction techniques and materials low in embodied carbon. Carbon emissions from the traditional construction materials and methods are colossal. However, as many firms pledge allegiance to Net Zero, Cross Laminated Timber (‘CLT’) emerges as a chance to tackle some of the deep-seated issues in conventionally erected structures. The adoption of CLT has surged over the recent past; major projects across the globe have warmly welcomed CLT into their building design and structure. There are a considerable number of such projects worldwide that are embracing CLT in their buildings' designs. In this article, we will find out information about CLT and see what difference between CLT and normal plywood. Also, it is a chance to learn about Vinawood, a leading plywood supplier in Vietnam.

What is cross laminated timber?

CLT stands for cross laminated timber. It is a type of engineered wood product formed by gluing layers of wood panels in different directions using structural adhesives, thereby greatly enhancing strength and stability as construction elements for building walls, floors, and roofs. Cross-laminated timber (CLT) is a type of engineered wood product that is made up of multiple layers of dried-dimension lumber (typically in sets of three, five, seven, or nine) that are laid out perpendicular to each other and then bonded together to create panels with structural capabilities. By bonding these layers at right angles, the panel gains strength and rigidity along both axes. There are instances where the outer laminations are parallel instead of the typical crosswise orientation— this is done under special circumstances. The process of manufacturing CLT begins with careful selection of lumber, removal of any defects, and cutting to appropriate sizes. This is followed by application of adhesive and laying up the panel, after which assembly pressing is done to ensure proper bonding. The panels are then cut to their final dimensions along with any prefabrication requirements before a thorough quality control check is conducted. Only after this inspection are the panels delivered to the construction site.Final quality control is carried out prior to delivery to the building site. CLT panels can be manufactured as custom dimensions, though transportation restrictions tend to dictate their size. CLT is manufactured in a controlled factory setting and must meet specific quality and performance requirements. The vast majority of CLT panels are made for a specific application with prescribed size, shape, appearance, and machined sections (e.g. recesses, holes, slots). Precise fabrication often relies on building information modeling (BIM) and other prefabrication technologies. Similar to other mass timber products, CLT panels can be topped with concrete to form timber concrete composite (TCC), a hybrid system used to reduce cross sections, increase spans and lessen noise transfer and vibrations.

What are the advantages of cross-laminated timber?

Sustainability

Cross-laminated timber (CLT) primarily uses spruce or other coniferous species, which are renewable resources that grow relatively quickly. This isn't the same as traditional building materials like steel, made from iron ore, or concrete, made from sand. The construction industry consumes the type of sand required for concrete faster than it can be replenished, causing significant harm to the natural environments from which it is mined. In contrast, the wood used in CLT comes from managed forests that undergo regular reforestation. The process of converting wood into CLT requires significantly less fossil fuel burning than the production of traditional construction materials. Recent research indicates a 60% reduction in emissions compared to reinforced concrete structures. Furthermore, timber serves as a far superior carbon store compared to concrete, steel, and masonry. When CLT panels reach the end of their usable life, they can be recycled or repurposed for other uses. Consequently, the demolition process for CLT structures is far less wasteful and hazardous than that for conventional structures. CLT can be used as an alternative to concrete to form the walls, roofs, floors and ceilings of a building, and is particularly well-suited to multi-storey taller wood construction. This can include pre-insulated wall and roof sections. Other applications include cantilevered floors and balconies, load-bearing elevator shafts and stairs. It can be used in virtually any building type from residential and office towers to schools and civic buildings. It can be left exposed for its aesthetic appearance or encapsulated when needed. Lumber in the outer layers of CLT wall panels are normally oriented up and down to maximize its load capacity vertically. Likewise, for floor and roof systems, the outer layers run parallel to the direction of the longer span Compared to solid wood, CLT panels are more stable and less variable in mechanical properties. As for plywood, CLT is made of layers of cross grain, thus they should be less prone to deformations at moisture content variations. Compared to glulam, CLT panels are typically used for box-framed structures, where entire walls and floors serve structural functions. In contrast, glulam structures exhibit a hierarchical design, comprising large glulam elements and secondary level elements.

Wellbeing

The importance of well-being in commercial real estate has accelerated over the past decade, especially in the wake of the COVID-19 pandemic. Wooden interiors benefit occupants by regulating humidity levels and temperature, and numerous studies indicate that wood has positive effects on individuals' physical and mental health, such as reducing blood pressure, stress levels, and fatigue.

Efficiency and Durability

CLT panels have a lifespan of over 50 years and are highly versatile, suitable for walls, floors, furniture, ceilings, and roofs. However, CLT and glulam panels exposed to the outside environment require additional surface treatment. CLT can also be integrated with conventional materials, as demonstrated by recent developments like 6 Orsman Road, a 34,000 sq ft office block in Haggerston completed in 2021, which is a hybrid of CLT, steel, and concrete.

What are the disadvantages of cross-laminated timber?

The positive aspects of CLT structures are numerous, but it is important to note that CLT structures are less easy to inspect for potential decay events, such as fungal rot attacks. In traditional solid wood or modern glulam structures, you can check the primary structure first and then move to the secondary elements. In CLT structures, however, everything holds equal importance, making the entire building the focal point of inspections. Here are some of the current disadvantages as adduced in various sources:

• CLT is more expensive than steel or concrete
• Code restrictions on timber building heights: Building regulations often limit the height of timber buildings, which can restrict the use of CLT in taller structures
• Costs of electrical, plumbing and other services can increase: Unlike traditional construction methods, CLT structures lack wall cavities, which can lead to higher costs for installing electrical, plumbing, and other services.
• There can be higher architectural/design costs: The unique characteristics of CLT may require more specialized architectural and design services, increasing overall project costs.
• A higher material transportation cost: Due to the relatively few manufacturing plants, transporting CLT materials can be more expensive. Less long-term flexibility: CLT structures may offer less flexibility for future renovations compared to traditional building methods.

A more serious concern regards the supply of raw material for CLT, as timber is a more costly material than its traditional counterparts. As demand for timber grows, construction costs continue to rise. Currently, the UK relies mainly on EU-sourced timber, the import of which not only has an environmental impact but is also dependent on trade policy between the UK and EU. If export and import tariffs on timber from the EU were to increase, there is a risk that CLT use in the UK could become unviable. However, research on the feasibility of sourcing more wood from Scotland is currently underway, which would help address this issue.As supply and demand for CLT increase, some of these disadvantages may well disappear. More plants and more production can drive down costs. More demand means more people with design expertise

What is the lifespan of cross laminated timber?

The CLT product has a lifespan of 60 years and there are occupied timber buildings in Europe that are over 700 years old. The key factor in the longevity of a timber structure is the management of moisture during the design stage.

What is the difference between CLT and plywood?

Cross-Laminated Timber (CLT) and normal plywood are both engineered wood products, yet they differ significantly in construction, properties, and applications.

Construction

CLT consists of multiple layers of solid wood boards, with each layer oriented perpendicular to the one below it. This cross-laminated structure gives CLT exceptional strength and stability. In contrast, plywood is made from thin wood veneers, with the grain direction of each ply positioned perpendicular to the adjacent layers. This cross-grain configuration also enhances plywood's strength and stability, though it differs in composition and application compared to CLT. What if cross laminated timber can be used instead of concrete?

Properties

CLT's cross-laminated design makes it incredibly strong and stable, making it ideal for large-scale structural applications. Its thick panels also offer better fire resistance by charring on the outside, which protects the inner layers. While plywood is strong and stable, it doesn't match CLT's structural capabilities and has less fire resistance due to its thinner layers. However, plywood's strength is sufficient for a variety of uses, including furniture and cabinetry.

Applications

CLT is predominantly used in large construction projects like multi-story buildings and bridges, thanks to its ability to be manufactured in large panels. This not only speeds up construction but also reduces the number of joints. In contrast, plywood is more commonly used in everyday applications such as flooring, roofing, and wall sheathing due to its versatility and cost-effectiveness.

Is CLT cheaper than concrete?

CLT's cost for materials and labor can be lower than traditional steel or concrete. Material cost savings may be as much as 15% for mid-rise residential buildings. This is because CLT is lighter, requiring a smaller foundation, which reduces overall construction costs. A building applied with cross laminated timber

Is cross-laminated timber expensive?

While Cross-Laminated Timber (CLT) itself is not cheap and is more expensive per unit than steel or concrete, the savings come from reduced labor costs. The number of construction workers required on-site is cut in half, and there are significant energy savings during the building's operations and lifecycle. This makes CLT a cost-effective option in the long run.

Is cross laminated timber waterproof?

CLT is made of plain timber and it can withstand the elements. Provided the material has at least 5 layers, it can be considered waterproof. However, producers do not recommend installing CLT panels without an exterior cover. In this article, Vinawood team aim to help you gain a better understanding of purple heartwood. Vinawood hope that the above article has assisted you in deciding whether purple heart wood is the right choice for your project. Please check our website for the latest Vietnam plywood news. Also, if you are considering purchasing Vietnam plywood, visit Vinawood's website for more detailed informations.