The Farmers Mart Jun/Jul 2016 - Issue 46 | Page 27

Fencing

Image courtesy of Woodbank Timber Ltd

therefore, have to be conditioned
to reduce the initial moisture
content - usually to around a
minimum of 28%. Also, if the
timber is correctly conditioned
prior to treatment, it is much less
likely to ‘split’ in service.
Timber conditioning can be
achieved either by natural air
drying methods, where the
harvested timbers can be held
in stock, both prior to and after
machining, to allow the moisture
content to naturally reduce to
the required level or by carefully
controlled kiln drying methods.
Ask your supplier how
they dry their timbers and
how they check the moisture
content of their timber prior to
treatment.
TIMBER PRESERVATION
Modern timber preservatives
have been widely used in the
UK, Ireland and Europe since
the demise of CCA over a
decade ago. Though some
of the co-biocides used in
the preservatives differ from
manufacturer to manufacturer,
almost all high pressure (green
& brown) contain copper as the
main active ingredient.
All timber preservatives must
now be submitted under the
Biocidal Products Regulation
(BPR) for approval. The UK
approval body is the HSE who
previously would have issued

an approval on a national
registration basis. Though an
approval through the BPR is a
long, complicated and costly
process, it ensures all products
approved are fit for purpose
and have a significant pack of
test data behind them.
As knowledge of these
modern preservatives grows,
so does innovation. It is likely
that there will be many new
preservatives launched in
the UK and Europe with BPR
approval in the coming months
and years. The key is to
remember that though they are
new to the market, many, many
years of independent testing
in multiple countries will have
already been completed and
fully assessed by the HSE (or
equivalent in other countries)
before it is allowed to be sold.
A BPR registered product and
a treater treating to BS8417 is a
winning combination to the long
service life of a timber fence.

Timbers that require the least
level of protection, for instance
internal building timbers, where
there is no chance of wetting,
are considered as Use Class
1. External timbers, which are
permanently exposed to the
weather and could be either
used in or out of ground contact,
require a higher degree of
protection and are designated in
Use Classes 3.2 (external, out of
ground contact) and Use Class 4
(external, in ground contact).
Timber treatment plant
operators should be fully
trained, and will ensure
treatments for fencing and
agricultural timbers are carried
out to meet either Use Class 3.2
or 4, to give an effective long
term protection.
Ask your supplier if their
treatment plant operators
are fully trained and to what
Use Class they are treating
your fencing and agricultural
timbers?

TREATMENT APPLICATION
As stated earlier, the level of
preservative treatment given to
timber can be varied according
to its eventual end use. Within
the industry there are Use
Classes, which define the typical
end use of the timber and the
appropriate level of preservative
protection required. The main
Use Classes range from 1 to 4.

USING TREATED
TIMBERS CORRECTLY
Finally, just like any product,
treated timbers have to be used
correctly. With exterior fencing
and agricultural treated timbers,
there are a few considerations
which are particularly important
at the installation stage that
you or your fencing contractor
should note.

• Any cuts or notches made
to the treated timbers
must be treated with a
suitable brush-on end grain
preservative to maintain the
integrity of the protection.
These are usually readily
available from your treated
timber suppliers.
• Only timbers treated to Use
Class 4 requirements can
be used in ground contact
situations.
• Treated fence posts must
not be re-pointed.
• The shortening of fence
posts should be avoided,
whenever possible. If
unavoidable, the cut end
must be treated with an end
grain preservative and must
never be used in ground
contact.
• Any pressure treated
timbers which are further
processed, for instance
planed or rip-sawn, must
be returned to your timber
supplier for re-treatment.
• Treated timbers should
not be removed from their
original installation and reused at a new location.
In summary find a supplier that
provides quality preservative
treated timbers in which you can
have real confidence. Then using
and installing them correctly,
will give you years of sound
performance around the farm.

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