By Dr. Johann E. van der Merwe, Senior Lecturer at the University of Pretoria
With attention increasingly shifting from the operational carbon footprint of our building structures to that embodied in our building materials, there is a noticeable increase in the number of (often tall!) mass timber structures going up all over the world. Although the northern hemisphere is leading this trend, we are seeing more and more timber structures going up not only in South Africa, but throughout our continent.
Timber is considered by many to be the material of the 21st century. Why? Because it is renewable, stores carbon instead of emitting it, and offers an excellent strength-to-weight ratio. Modern timber technologies also allow for rapid, precise construction with less waste—making it a smart and sustainable choice for the future.
The shift to a greater uptake in timber is here. The question is: are we ready? Through teaching, research and industry engagement, the University of Pretoria is actively working toward ensuring that we are. Unfortunately, many misperceptions exist when it comes to building with timber. Let’s tackle those one by one.
Misperception #1: Timber is an alternative building material
Timber for sure offers a good alternative to our intensive use of concrete and steel. But timber is by no means an “alternative” building material – it is perhaps one of the oldest building materials around. Moreover, most of us go to bed at night with timber structures over our heads. Add to this our vast suite of local SANS standards from production to the structural design of timber elements, timber should rather be considered as a well-established building material that should be the go-to alternative to our excessive use of concrete and steel.
Misperception #2: South African timber isn’t good enough
This is a myth we’re actively debunking through rigorous testing at the University of Pretoria. Several ongoing studies are investigating the spread of mechanical properties of our local softwood and hardwood species. Results suggest that our local timber compares well with the grades of timber used most often in European timber building construction.
Misperception #3: Timber can’t handle fire or water
Mass timber elements behave predictably in fire — forming a protective char layer that slows down combustion. In fact, mass timber elements will most often outperform structural steel during fire exposure (Figure 3). We do need to take the combustible nature of timber into account in structural design, just as we have to consider similar sensitivities of other materials in fire.
We need to remember that no building material performs well in fire or in wetting and drying cycles. Nature has devised a way of getting rid of timber, and I believe we should consider this as a positive characteristic of timber. Centuries-old timber structures have shown, however, that with well-considered conceptual design, there is no reason for timber buildings not to last as long as those built with any other material.
Misperception #4: Timber is a silver bullet for zero-carbon construction
While timber offers major carbon savings, it’s not a magic fix. Most buildings will still require reinforced concrete cores and foundations, or even structural steel to support long spans. Reducing the embodied carbon of building structures is a complex task that must consider designing in a way that will prolong the usefulness of building material for as long as possible, building in pragmatic forms that provide the simplest flow of forces from superstructure to foundation, and the use of low-carbon materials. Timber is therefore no silver-bullet solution, but it is an indispensable part of the solution.
Misperception #5: We don’t have local expertise
… or should I say, “partial misperception”? Very few civil engineering curricula in South Africa currently expose students to timber structural engineering. Although we have some structural engineers in South Africa who have experience in structural timber design, the result is that we need more. At the University of Pretoria, we are fortunate to have modules at the undergraduate and postgraduate levels focusing on this point. With UP producing about a third of all civil engineers in South Africa, we are well-positioned to support a growing timber engineering industry.
National initiatives like the Talking Timber webinar series, WoodApp, and the Growing Timber Connections colloquium and conference are building critical industry momentum.
The road ahead
Timber construction is here to stay, and we should embrace this as an opportunity to drastically reduce the embodied carbon of our building structures that will support a growing population in Africa over the years to come. We have the timber, we have the standards, and we have the knowledge to do so.
References
Bowyer, J., Bratkovich, S., Howe, J., Fernholz, K., Frank, M., Hanessian, S., Pepke, E. (2016). Modern tall wood buildings: Opportunities for Innovation. Minneapolis: Dovetail Partners. Inc.
About the Author
Dr. Johann van der Merwe
(Pr.Eng, Dr.sc. ETH Zürich) completed his bachelor’s degree in civil engineering (2007) and master’s in structural engineering (2009) at the University of Stellenbosch, South Africa. He obtained his doctorate at the Swiss Federal Institute of Technology in Zurich, Switzerland (ETH Zürich) in 2019. After several years working as a structural design engineer on projects across Africa, Australia and New Zealand, he joined the University of Pretoria in 2023, where his research interests focus on timber structural engineering and improved circularity of building materials.