FEATURES
There are a number of benefits for using timber in construction.
up only a fraction of tertiary course work, which results in
successive generations of engineers prescribing a material
with which they are more familiar (like steel, brick or
concrete), even if a customer requests that timber be used,”
comments Dowse.
LIMITATIONS OF TIMBER CONSTRUCTION
According to Cronje, “There are very few limitations when it
comes to timber construction and as technology evolves,
these are becoming even fewer. In South Africa, SANS
10082 limits the height of a timber building to single- and
double-storey timber homes; any taller than this, and the
project will be deemed a ‘rational design’ which needs to be
structurally designed and signed off by an engineer.”
“Further limitations of timber construction include
building into the earth (such as with basements, which need
to be executed in concrete or brickwork) and building on a
common boundary, due to fire regulations. In tall timber
buildings, the fire escape and lift shafts are typically still
done in concrete, but this is really a minor ‘limitation’ to the
use of timber.”
Slabbert notes, “SA Pine structural timber is available in
up to 6.6 metre lengths, restricting very long spans with a
single piece of timber. That said, engineered beams, like
laminated timber beams or I-beams can span much longer
lengths, but will come in at a higher cost.
“Skilled labour is required to build timber structure as
opposed to brick and mortar,” says Slabbert, explaining,
“Brick-laying or wet works can be learned fairly quickly and
easily, but the art of carpentry is taken up through a longer,
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more tedious schooling process, resulting in a higher cost
of labour.”
ECONOMIES OF SCALE
According to Dowse, building a well-designed and approved
timber building in South Africa in the current climate will
come at a slightly higher cost than brick and mortar. “This is
because we do not have the economies of scale yet and low
volumes come with various price influences, including,
among others, the availability of timber components
required for optimal building,” he says.
“With around 80% of all structural timber produced in
South Africa going to roof trusses, it is not economically
feasible to produce the full range of products without
supporting sales volumes. In the US there are four or five
different structural grades available for South Africa’s two,
and almost double the number of dimensional
combinations. In South Africa, however, requiring a 120mm-
wide component would necessitate over-design due to
being limited to either a 114mm or a 152mm component,”
Dowse reasons.
“The same is true for engineered products like cross
laminated timber (CLT), veneer boards and glulam. The first
CLT manufacturing plant in South Africa is only now starting
up in Cape Town with low volumes. These manufacturing
plants require big capital investment and therefore large
sales volumes to keep the production and other costs at an
affordable level; without a steady timber building market
See more on page 52