Timber iQ February - March 2018 // Issue: 36 | Page 17

COVER STORY
Each curved and twisted beam received a smooth, planed finish.
Each beam was curved by hand following exact specifications.
The arch that celebrates Archbishop Desmond Tutu being assembled.
to penetrate the wood. With a lifespan of more than
50 years, Siberian larch is one of the toughest and
most durable softwoods available. This durability is
like our architectural western red cedar.
The laminated beams were tested to the force of
8.6kN which is equivalent to the minimum requirement
for a grade 8 MOR test. The MOE is calculated as
15 841 megapascal (mPa).
Siberian larch is common mainly in regions that have
very blunt and rather dry climates (average 65%) with
extreme temperature changes (in summer up to 40°C
and in winter down to -60°C), larch grows very slowly
and very dense.
Larch species' dendrological particularities in
combination with the harsh climate also create this
high-quality wood, which is comparable to the
precious wood and hardwood. The most valuable types
of Siberian larch wood are considered those that grow
in very cold climates because these areas have a long
growing larch, which is a little branchy and is dense
and relatively easily supplied from the felling areas to
saw mills.
Larch timber is famous worldwide for its unique
biological and physico-mechanical properties.
Therefore, it can be classified as one of the most
valuable building materials. Larch wood consists of up
to 90% heartwood, which is very hard and sapwood is
only 10 to 20mm. Since it is grown in unaffected
Siberian forests, it practically has not faced man-made
pollution. It is not only ecologically clean wood, but
even has medicinal properties. Larch wood has special
substances called phytoncides that are released from
the wood throughout the whole of its life cycle.
Phytoncides spread in the air and purify it from
harmful microbes and so there are very few viruses
and microbes in the space around larch wood trees.
Siberian larch has a high fire resistance and low
thermal conductivity but larch's resistance to rot and
pests is specifically highlighted; thanks to its special
resin, which has a variety of chemicals, which fulfils
the function of natural antisepsis. Therefore, larch is
very resistant to rot and pests.
Larch will serve you two to three times longer than
other species of conifers, without additional chemical
treatment, while other tree species need chemical
treatment. So, larch material does not necessarily have
to be treated with impregnates – plus due to its density
– the wood absorbs impregnate very poorly. Also, the
fact that in construction, chemically saturated material
is not used, which is a very important element from a
fire protection point of view. In the case of fire, larch
reduces the risk of a
poisoning with chemical
(antiseptic or
impregnate) vapours or
carbon monoxide, which
can cause a person to
lose consci ousness.
// FEBRUARY / MARCH 2018 15