By Jamie Smily, owner of XLAM South Africa (Presented at the Wood Conference 2020) | All photos by XLAM

The construction industry is in the midst of a paradigm shift, which promises to revolutionise the way we design, engineer and build.

An example of an off-site construction of a cross laminated timber (CLT) cabin.

An example of an off-site construction of a cross laminated timber (CLT) cabin.

When we consider timber construction in South Africa, the general public think of a ‘wendy house’. Perceptions are truly the biggest hindrance in the timber construction space. Is timber biosafe? Will it survive an insect attack? Surely it can burn down?

We need to be rethinking the way we use timber because it is no longer a material that is just suitable for small structures, or parts of a structure. It has already become material used in the entire structure and body of many buildings.

Setting the record straight

Timber in South Africa has been seen as an inferior material, but in fact it is a great material. We have an incredible forestry sector in South Africa, and we have very good institutions who are watching what is being built and how it’s being built.

There is the South African Wood Preservers Association (SAWPA) who are looking at timber treatments. There is the South African Technical Auditing Services (SATAS) who are auditing companies to make sure that for example Glulam beams or structural timbers that you are buying are in fact what they are meant to be.

5-Ply cross laminated timber (CLT), 165mm thick.

5-Ply cross laminated timber (CLT), 165mm thick.

There is a whole range of South African National Standards (SANS) and some timber products used as alternative building technologies also fall under, and require, the Agremént certification. Timber is already part of our building regulations – it falls under SANS-10400 codes for structural timber and timber framed construction.

There is further, development of a standard for the manufacture and use of cross laminated timber (CLT) which is in its final stages of approval. This South African standard is quite an achievement for the industry as there are many other countries who still do not have their own manufacturing standards.

The other point often referred to has to do with sustainability – ‘how can timber be sustainable if you are cutting down the forests?’ In this case it is important to use timber endorsed by groups such as the Programme for the Endorsement of Forest Certification (PEFC), the Forest Stewardship Council (FSC), and so on who check that timber materials are coming from sustainable resources.

A finished cross laminated timber (CLT) staircase.

A finished cross laminated timber (CLT) staircase.

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.

Timber’s credentials

The environmental benefits of using timber are great. The main subject that is spoken about is CO2 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.

“There is currently a South African standard for the manufacture of CLT in its final stages of approval.”

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 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 CO2 – this is the direct advantage and saving using timber over concrete. If you consider timber buildings in other countries and the total CO2 savings being made, these are huge figures that are seen on a single structure, imagine the impact of large-scale implementation.

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 material. There are a few steps along the way that we have to make sure are correct in order to maintain quality, as this is a major element in engineered timber products. Moisture is a key factor, so you must ensure that you have the correct moisture levels before laminating.

This quality control process is very well ingrained in the European CLT production lines – they are relatively new in South Africa but the fact that we have a standards developed is already a big step forward for the industry to allow us to create these materials locally, and know that we are creating the right strength and quality of the material for its application.

Benefits of using mass timber in South Africa

One of the benefits of using mass timber in South Africa is the increased speed of construction. A lot of this is to do with these materials being produced in a factory and being converted into components before being taken to site.

Timber is also a lightweight material, a fifth of the weight of concrete. This means that you can have smaller foundations, or that you can build higher on the same types of foundations. This is a great benefit for existing buildings in city areas that have been given an allowance to increase in size (bulk) but it tends to be too expensive because you would have to work on the foundations before you could increase the size of the building. With timber being a lightweight system, it allows for additions onto existing structures easily, often without the need to relook the foundations.

There is also the potential for job creation. While most of the European production facilities use a high level of automation, our local processes are much more hands on, creating new skilled jobs within the factories.

Manufacturing and processes

Timber has all of the positives already mentioned and further to these it is a material that lends itself to modern machining extremely well. With technology you are able to manufacture very precise products through the ‘design for manufacturing and assembly’ process (DfMA).

DfMA is the process of designing elements in a way that allows for easy and precise assembly. What DfMA and the use of timber and modern machinery allows us, is that with a little additional planning upfront, we have significant savings on the installation time and associated issues that come with installing the structures on site.
Everything comes back to the design process and pre-planning. Pre-planning is loved by engineers because it means less onsite changes. You also get a very reliable cost model allowing for incredibly efficient results. The equipment used to create these elements in mass timber production is typically large CNC machines but also can include industrial robots that assist in the manufacturing process and even possibly on-site installations.

This technology allows us to, for example, take an entire wall and cut the openings for windows and doors, cut the reticulation into the panels so that the electrics and plumbing can already be integrated, and all of this allows for very large projects to come together from the model stage to reality in record time.

Further, the process can allow for various complex sub-assemblies to take place. A factory can manufacture an entire façade of panels, the interior and exterior, then bring them in section by section and install on site. The panels simply are packed onto a truck and then transported to site and erected within a few hours.

In other countries like the US, some companies have invested heavily in what is known as off-site construction facilities and are manufacturing, as an example, an entire hotel room with furnishings and components – these are then brought to the site and installed. This method of construction has been used in Amsterdam and New York, where running a traditional construction site is very difficult. You could imagine in a city like New York what would happen if you had to close roads off. This method of off-site construction is so efficient it has been referred to as the construction industries ‘Uber moment,’ a paradigm shift in the way we build the world around us. It offers the possibility to build faster, safer and more sustainably.

All in all, between timber’s properties, technology, structural methods and various sub-assembly configurations available, mass timber holds great and wonderful potential in South Africa.