Cross Laminated Timber (CLT) as Sustainable Material

Although the change is extremely slow, it's welcoming news that people are now looking for more sustainable options for their designs. Cross-laminated timber or CLT is one such material. 

Cross-laminated timber, as the name suggests, is lumber (from the same log) glued together perpendicular to each other for more strength. The number of layers is mostly odd, although this number varies based on requirements.

Advantages

1. Sustainable

Since it is made from pieces of wood glued together, CLT is extremely sustainable. This reduced the carbon footprint.

2. Lightweight

Cross-laminated timber is extremely lightweight, but strong, making it perfect for high-rise buildings. It is also perfect for constructing buildings where the land might not be able to support heavier ones.

3. Thermal Insulation

Since CLT is made by gluing multiple layers of timber, it has considerable thermal insulation properties. The level of insulation depends on the number of layers.

4. Prefabricated Pieces

CLT walls, floors, other structures, and even entire modules can be prefabricated and transported to the construction site. This further reduces the need for heavy and time-consuming machines.

5. Less Time For Construction

Since CLT can be prefabricated, the time required for construction is reduced greatly. 

6. Ease Of Construction

CLT offers a lot of options and flexibility for customizing. The thickness, strength, shape, etc. can be changed depending on the project requirements. 

7. Cost Of Construction Reduced

The need for less machinery and labor during construction reduces the cost required for these. Although transportation and material charges may add up if it is not locally available.

Disadvantages

1. Cost

Since CLT is still not a popular building material, there aren't a lot of manufacturing units. If there are no manufacturing units near the site, the cost of manufacturing and transportation is very high.

2. Fire-resistance

Timber is known to be a flammable material. And in case of a fire, there is a possibility of collapse. However, the surface of the cross-laminated timber can be treated with fire-resisting chemicals to improve its integral resistance against fire.

3. Acoustic Properties

CLT is not the first choice if you're looking for good acoustic options. However, increasing the number of layers or adding minerals in between layers can improve it.

Manufacturing

Cross-laminated timber is mostly manufactured in its specific manufacturing units and assembled on site.

1. Timber Selection

Based on the requirements, good quality timber is carefully chosen after testing its properties. Based on these tests, two types are categorized:

• Construction grade CLT: Timber which has good structural and load-bearing properties
• Appearance grade CLT: Timber which has aesthetic properties

2. Grouping

The timber is then grouped based on these grades. Construction grade is used on interior walls and appearance grade is used on the exterior for aesthetic purposes.

3. Lumber Trimming

In this step, the selected timber is trimmed on the top, bottom, and sides to ensure a smooth and equal surface. Usually, 2.5 mm is trimmed off the top and bottom and 3.8 mm is trimmed off the sides. This leveled timber is then cut into smaller pieces based on requirements.

4. Applying Of Adhesive

Glue is applied to the surface in an airtight atmosphere to ensure that no bubbles or air holes are formed. These layers are then stuck firmly together.

5. Pressing

There are two types of pressing methods:

• Vacuum pressing: This method is both energy and time efficient, as more than one CLT panel can be pressed at a time.
• Hydraulic pressing: This method applies higher pressure while pressing than the former.

6. Giving A Better Finish

Machines like the sanding machine are used to give a smooth finish to the freshly manufactured CLT panels. Finishes and chemicals may also be added to further enhance their properties.

7. Construction

Floors, walls, ceilings, and even furniture can be made out of CLT panels.

• The manufactured CLT panels are cut according to the required size and shape.
• Joints, openings, and drills are made in the manufacturing units themselves.
• Sometimes these panels are arranged as modules before being transported to the site.
• The arrangement of these modules is quick and dry, meaning no further materials are required for further processing.
• Once assembled on site, the final setup is enhanced with finishes to improve its visual and functional properties.

Cross-laminated timber is completely made of renewable sources, making it an excellent option for sustainable building materials.

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