Natural wood is a material that has been used in building projects in numerous forms for thousands of years. However, many new wood-based products have been developed over the last century, enhancing the original properties of natural wood and offering greater strength and durability. One such material is cross laminated timber, which is being increasingly adopted in the construction industry as a better substitute for natural wood. Continue reading to understand exactly what cross laminated timber is, how it’s made, its benefits and applications in construction and the CLT cost in India.
What is CLT (Cross Laminated Timber)?
Cross Laminated Timber (CLT) is an engineered wood product made by glueing together multiple layers of thick solid wood panels. Each layer consists of kiln-dried lumber boards with wooden grains that are perpendicular to their adjoining layers, thus giving the CLT panel high strength. It is similar to plywood, but has thicker wood layers and can be used even in structural applications in buildings.
How is Cross Laminated Timber Made?
The manufacturing process of CLT typically follows the below steps:
- Lumber Selection: Lumber panels arrive at the factory and are selected based on their physical properties. Visual checks are conducted to ensure that no defects in timber are present. The wood used for making CLT layers must have a moisture content lower than 15%. After this, the wooden panels are grouped based on their moisture content – the difference in moisture content between each layer must not be more than 5%.
- Trimming and Cutting: All the surfaces of each wood panel are trimmed by around 2.5 – 5mm to produce smooth surfaces. The panels are then cut to specific lengths.
- Finger Jointing: The wood panels are generally elongated elements with a width of around 50- 200mm. These panels are fixed to each other by finger-jointing or dovetail joints to produce one single layer of the CLT board with a width of 600-1200mm.
- Gluing and Assembly Pressing: Individual layers (each with a thickness of 20-60mm) are laid with their grains perpendicular to each other and glued together. These layers are then bonded together by using a vacuum or hydraulic press to ensure maximum adhesion. The minimum number of layers is three, but the maximum number can go up to 9, depending on the total thickness required.
- Finishing: The CLT panels are cut to the required size and the holes, joints and other additional fixtures (as needed for specific components like windows or wall panels) are installed. All the exposed surfaces of the panels are then sanded and polished to ensure a smooth finish.
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Benefits of Using CLT Lumber
- Sustainability: While conventional concrete and steel structures generate high amounts of CO2 during their manufacture and construction, CLT building construction is not carbon-intensive. It is made of natural materials and can also be completely recycled or reused as reclaimed wood, making it more sustainable.
- Thermal Insulation: Cross laminated timber panels have high density and thermal mass. This means that they don’t allow heat to easily escape from buildings, thus reducing the amount of energy used by mechanical ventilation systems.
- Strength to Weight Ratio: With extremely low weight, laminated timber products provide high strength and stiffness that is almost equal to RCC elements. This lower weight reduces the loading on foundations, thus decreasing the foundation and project costs.
- Fire Resistance: Steel and natural solid wood can resist fires for around 15-20 minutes. However, CLT structures can resist fires for 90 minutes. This is because their outer layers get charred during fires, protecting the inner layers from burning.
- Earthquake Resistance: Unlike rigid framed RCC structures, joints between CLT structural members have a certain amount of flexibility. This flexibility helps in dispersing tectonic waves safely during seismic events, thus aiding in making buildings earthquake-proof.
How is CLT Wood Used in Construction?
Structural Applications of CLT
- Slabs and Flooring Systems: CLT panels can be used to form one-way and two-way slabs in both load-bearing and framed structures. These slabs are generally supported by CLT or steel beams/ rafters/ braces. They can also be used along with concrete to form composite slabs that have high stiffness.
- Roofing Systems: Sloping roofs as well as shell structure roofs in hyperbolic, parabolic and other curved shapes can be made with CLT timber construction. Such roofs are lightweight, but can maintain extreme rigidity. However, they need adequate surface treatment to prevent water seepage and rotting due to rain.
- Walls: CLT walls with a minimum thickness of 80mm have a high load-bearing capacity. They can be erected much faster than conventional masonry construction, thus reducing project timelines.
- Structural Supports: Beams, lintels, sills and braces are some of the structural supports that can be made with CLT construction. Such elements can be used to stiffen the walls, floor, ceiling or roof panels in buildings.
- Staircases: CLT can be used to make different components of a staircase, including risers, treads, railings and supporting posts; as well as the entire staircase unit itself.
Non Structural Applications of CLT
- Wall and Ceiling Panels: Interior as well as exterior cladding panels can be made with CLT as a substitute for solid wood or veneers. This retains the natural look of solid wood while being more cost-effective and sturdy.
- Interior Elements: Non-structural interior partitions, furniture, storage cabinets and decorative items are some of the other cross-laminated timber structures that can be used in the interior design of buildings.
Cost of Cross-Laminated Timber Panels
Cross-laminated timber panels are generally available in sizes of 4’x8’, 2’x10’ or 2’x6’, with thicknesses varying from 60-300mm. However, it is not very easily available in India as it is still a new material in the market and its applications in construction are still being explored. Its price usually starts at ₹500/sq ft and can go up to ₹3500/sq ft, depending on the type of wood used, brand, location, availability, thickness, size, quality, market trends and other such variable factors.
Using Cross Laminated Timber in Your Project
Since it is still a new material, CLT can be difficult to source and even more difficult to judge its quality. Expertise and industry knowledge are required to use such innovative materials in building projects. However, Brick & Bolt is a tech-enabled construction company in India that strives to incorporate new materials like cross-laminated timber in its projects. The company associates with India’s leading manufacturers and brands to ensure the supply of the best quality building materials and provide assured quality. To get your dream home or commercial building designed and executed by India’s top construction company, reach out to Brick & Bolt today!
Apoorva H P Achar 
Hemali Patel