Timber iQ October / November 2020 | Page 29

TALKING TIMBER materials, we just have to find ways of being less dependent on them, finding alternative routes to alternative materials. A simple example: a cubic metre of concrete replaced with a cubic metre of wood equates to one ton of CO 2 – this is the direct advantage and saving using timber over concrete. If you consider timber buildings in other countries and the total CO 2 savings being made, these are huge figures that are seen on a single structure, imagine the impact of large-scale implementation. 5-Ply cross laminated timber (CLT), 165mm thick. The perception of the timber used in construction needs to change. Timber that is being used in construction and engineered products, is a crop. Forestry companies are growing a plantation of timber that gets harvested every couple of years, and in fact are responsible for afforestation as they are planting more trees every year than what are harvested. So, when we see these plantations – yes, these are a beautiful and natural environments, but we do need to understand that this is a crop to be harvested and used. There is currently a South African standard for the manufacture of CLT in its final stages of approval. WHAT IS MASS TIMBER? For the structural side of building, we have what is known as mass timber. There are a range of timber products that fall under this category, and to name a few: • Glulam which many people would already know about. • CLT or Cross Laminated Timber, which seems to be the darling of the moment. • LVL or Laminated Veneer Lumber, which has been around for some time. • Nail laminated lumber. • Dowel laminated lumber. • Mass plywood. With these products, we are taking timber and typically gluing them together in different formats to make a new material that no longer has a wide variation of strength values, but is a far more homogenous material, allowing for predictable structural calculations. Creating these products is through layers or cross layers. The cross laminated timber (CLT) is made as it is named – by taking lamellas of timber (smaller sections of timber) and gluing them at 90 degrees to each other. It is a fairly complex process, mainly due to the nature of the timber, and there are a lot of checks and balances in the quality control process which are needed to ensure a reliable structural TIMBER’S CREDENTIALS The environmental benefits of using timber are great. The main subject that is spoken about is CO 2 sequestration or seizure into the material. We often only look at the operational life of our buildings and SANS-10400-XA (the sustainability requirements of our building code), relates to how much energy will be saved in the lifespan of the building. We tend to neglect the embodied energy it takes to erect these structures, and this too needs to change. Timber plays a huge role in embodied energy of a building (this is the energy we are using to prepare the concrete to be used, or mining and smelting steel). In the process of growing trees, you have the trees growing and at the same time absorbing carbon and releasing oxygen, which helps counter greenhouse effects. Once the trees are felled, the carbon is locked into the tree, so you are actually locking carbon into the material itself. This is very different to materials such as steel or concrete where you have to burn lime and ash to create cement. Mining for steel production is a very intensive process, aluminium also requires a huge amount of energy to produce – all these materials are recyclable too, but if you look at the comparison in embodied energy, timber allows us to build a structure that is carbon neutral, if not carbon negative, where this is almost an impossibility using other traditional materials. It is a given that we are always going to use traditional materials as they have been with us for thousands of years – they are good A finished cross laminated timber (CLT) staircase. www.timberiq.co.za // OCTOBER / NOVEMBER 2020 27