Timber iQ December 2018 - January 2019 // Issue: 41 | Page 55

TALKING TIMBER
UNDERSTANDING EXPANSION AND
CONTRACTION
It is important to understand that wood is a natural
material, and it expands and contracts. This is because in
nature, microscopic cells within a tree expand and absorb
moisture from its environment, or as water flows through
the wood to nourish and sustain the life of the tree. These
cells contract, or shrink, when the water evaporates.
Even after being cut down and processed, timber will
continue to expand and contract as it absorbs moisture
from its environment during the wet season and loses
moisture during the dry season. For this reason, it is
important to not only seal the timber correctly to minimise
moisture intake, but also to take various preventative
measures to protect the wood from exposure to the
elements as much as possible.
Lourens says that it is perfectly normal for wooden doors
to take a while to adjust to the specific ‘micro-climate’ of
their location. “It takes a while for any timber door to adapt
to the equilibrium moisture content (EMC) of the area,”
highlights Lourens. EMC is a term used to explain the
amount of moisture in the air that all natural products will
adapt to when exposed to a particular micro-climate. For
example, in Hout Bay in the Western Cape, there is a very
high EMC, averaging at 15%, while the average EMC for
South Africa is 8%. To cater for all the various areas
throughout South Africa, from wettest to driest, Swartland
dries its timber to an average moisture content of 10%.
“As newly installed doors come into balance with the EMC
of the area and the orientation of its installation, it will
swell slightly during the wet season, and shrink slightly in
the dry season. As a general rule of thumb, wooden doors
will settle after two seasonal changes – after which, the
doors might need slight adjustment,” he explains.
RAY BANS
“To protect your wooden doors, you need to protect them
from exposure to excess rain, as well as from the sun’s
harmful UV rays, which can dry out the timber and cause it
to shrink,” notes Lourens.
He says that you can protect your wooden doors by
planting fast growing, evergreen trees that will offer them
access to natural shade. “This will prevent your door from
being exposed to UV rays for any extended period of time
and offer the bonus of some well appreciated greenery
around the entrance,” Lourens explains.
The colour of the door you choose can also help, notes
Cobus, saying that, “Choosing a door in a light colour will
help it to cope better with UV rays, compared to one in a
darker colour. This is because light colours reflect the heat,
while dark colours absorb it.”
HAVE YOU GOT IT COVERED?
However, according to Lourens, aside from regular
maintenance, probably the best preventative measure to
increase your wooden doors’ longevity is to include an