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