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Posts and poles
Timber posts and poles are used for building, fencing, playgrounds,
transmission lines and other applications. In some regions
there are attractive markets for large poles. This makes poles
a more valuable product than sawlogs. Depending on their purpose
the product specifications for posts and poles may be based
on length, diameter, taper, species, durability, strength
and age.
Although the prices are good, only very high quality, tall,
straight, highly durable species have been traditionally sold
for telegraph poles. Having said that, preservation treatment
has allowed less durable species to be used and trials are
underway with plantation eucalypts. But eucalypts’ impermeable
heartwood makes them difficult to pressure treat with preservatives.
The specifications for posts can also be extremely tight and
it is common for only a small proportion of any harvest or
thinning to meet the specifications. For example, the recent
expansion of vineyards has increased demand for small diameter,
treated pine posts. But a single tree might yield only one
or two short posts that meet the tight market requirements,
while the market for other sized posts might be flat. There
have also been problems with the low density and strength
of small diameter treated pine posts from young plantations.
This has led some processors to specify that posts must be
a certain age.
Consumer concern over the use of the commonly used preservative,
Copper Chrome Arsenic (CCA), has renewed interest in naturally
durable timbers. Although many species harvested from native
forest are classed as highly durable, questions have been
raised about the durability of the same species when grown
in plantations and harvested at a young age—for example,
trees younger than 15 years. Growers should not assume that
young trees will exhibit similar properties to those harvested
from mature native forests, even where the log size is similar.
Wood properties
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