I have been touring London for the past few days, and yesterday I visited three cross laminated timber buildings. That is what compelled me to write this blog. Observing the structures got me thinking about why this is not practised on a larger scale in the world? The construction industry is one of the largest waste generators in the world. According to the Building Material Promotion Council, India generates 150 million tonnes (approx) of construction and demolition (C&D) waster every year. So, shouldn't we transition and use sustainable methods? This blog is about answering these questions on sustainability by exploring cross laminated timber as a solution.
List of Contents
1. What is cross laminated timber?
Cross laminated timber (CLT) is made by glueing layers of timber planks at right angles to each other, using non-toxic adhesives. Generally, there will be 3, 5 or 7 layers of timber, each approximately 22mm thick.
2. Meeting Architect Andrew Waugh
I met Andrew Waugh of Waugh Thistleton Architects in London. He told me that everything needs have to be planned well before beginning the construction. According to him, the number of trees which will have to be cut is four per person.
It is becoming a slow trend, and there are 400 buildings now. CLT is being imported from an Austrian plant. According to my understanding, factories may be found in Sweden, Germany, the United States, and Canada. In addition, two factories will be built in the United Kingdom.
3. Uses of CLT
In both load-bearing and non-bearing structures, CLT panels can be utilized for walls, floors and roofs. It was primarily used in the construction of low and mid-rise buildings. But in recent years, it has become a popular choice for high-rise construction. It has proven to be a good alternative for concrete and steel because of its good strength-to-weight ratio.
4. Benefits of Cross Laminated Timber
The buildings I saw are wholly made of timber. The first one I saw was a 9 storied apartment building called "Stadthaus, 24, Murray Grove". It was the tallest CLT building at that time in the world. Waugh Thistleton Architects themselves are building a 25 storied building now. The lift shaft, floors, staircase, walls and facade are made from timber. 11 lorry loads of cross laminated timber sheets were used in constructing it. A concrete structure of the same proportions would have taken 4 times the load. The construction of the building was completed within a year in 2008. Four carpenters assembled the entire CLT panel building in just 27 days. The dimensions are precise and have great thermal as well as acoustic properties.
The CLT is made out of pine timber. The CLT panels are manufactured in long sheets, and they are complete with cutouts for windows, doors and all the services. The CLT panel construction involves joining different cross laminated panels using 75 mm GI brackets. Considering that concrete and steel account for more than 15% of greenhouse gas emissions, the building becomes carbon negative. According to Waugh, making the building carbon neutral will require 29 years of service use. So these buildings are very eco-friendly.
5. Disadvantages of Cross Laminated Timber Buildings
Perfection is a myth in this world. Similarly, CLT also has some disadvantages like:
Because CLT is a relatively new material, it is not widely produced. Furthermore, compared to traditional stud walls, the production of CLT panels demands a significant amount of wood and other materials.
CLT has a limited track record because it is a new material that hasn't been used in many construction projects. Even though several technical studies have been conducted on the subject, it takes time to adopt diverse methodologies and outcomes into the business.
Wood, unlike other construction materials such as steel, is inherently combustible.
6. Conclusion
I think it is time we introduce cross laminated timber in India because CLT buildings are lightweight, they save time during construction and money when it comes to laying the foundation. Using more and more timber without planting trees is of no use. This action only increases the pressure on the environment, and hence, will not be sustainable. Thus, when cross laminated timber is used in buildings, an equal amount of trees must be planted. Using CLT with reforestation can save the environment and the buildings. Timber and CLT is definitely the future building material because it is the only thing that can be grown again after being cut down.
