51 / 64
49
CONSTRUCTION WORLD
SEPTEMBER
2016
WOOD CONSTRUCTION
This increases the durability
and resistance to fungal attack,
wood borers and termites. This
pre-treatment prior to use is
prescribed in SANS standards and mandatory
compliance is regulated through regulations
and compulsory specifications, along with
third party product certification.
Supplemental or remedial preservatives
on the other hand contain biocides which are
included in mainly solvent or oil based solu-
tions (in some cases wood finishes or sealers),
and are applied in a DIY setting by brush, paint
or spray to stop further attack. These require
an on-going maintenance program to remain
effective as it is merely a surface application
with minimal penetration.
It’s important to note that most exterior
wood sealers or varnishes, contain no
biocides and only protect against weath-
ering, moisture and UV rays, but not against
fungal and insect attack and should rather be
referred to as protectants than preservatives.
Why preserve timber?
The natural durability of our commercially
grown and used plantation species like Pinus
and Eucalyptus (gum), is low, rendering it
susceptible to insect and fungal attack; there-
fore it is imperative to preserve the timber.
Choosing the correct treated
timber
The following SANS standards apply to
treated timber:
• SANS 457 – droppers, guardrail posts,
building, fencing and agricultural wooden
poles
• SANS 753 and 754 – wooden poles for
transmission and telephone lines.
• SANS 1288 – All other preservative treated
timber, e.g. sawn structural, flooring, etc.
These standards specify a Hazard Class
system (H Classes), which categorises treated
timber into different end-use applications
based on different exposure conditions and
risk of biological attack.
Product use information
Be sure to choose the correct H class timber
for your intended application and apply
remedial preservative to all cross-cut and
exposed areas (except when in contact with
the ground, fresh water or marine applica-
tions). Do not plant poles inside an encapsu-
lated concrete base. Instead, use a ‘collar’ or
compacted stone and soil with or without a
solid (cured) concrete base.
How to plant a pole
Understanding
WOOD PRESERVATION
There are two types of wood preservation; primary
(industrial) and secondary (DIY). Primary wood preservation
is the impregnation of timber with a wood preservative
chemical like CCA, Creosote, Borate, TBTN-P or Azole
Permithrin, using prescribed industrial processes.
Safety precautions and
warnings
When sanding and sawing CCA treated wood
wear a dust mask and safety glasses, and
work in a well-ventilated area. Wash work
clothes separately. Treated wood must not
be used for: firewood, baby toys, furniture
which may be chewed on by infants, food
utensils or storage containers, beehives, nor
should treated wood shavings or sawdust be
used for animal litter or where it can become
a component of animal feed.
Disposal
Treated timber waste is not regarded as
hazardous waste material; however, treated
wood off-cuts and waste should not be
allowed to accumulate, but should be
disposed of at a registered disposal or landfill
site. It is important not to burn treated wood
off-cuts and waste or use it firewood for food
preparation, as this will allow the release of
chemicals, which are tightly bound to the
wood, into the smoke. The ashes may also
contain residual chemicals.
H5 – High Hazard: Outside in contact with heavy
wet soil or in fresh water (piling, substructure for
walkways and jetties, vineyards, etc.)
Choose the corect hazard
(H) class
H6 – High Hazard: Ptolonged immersion in
sea water (marine piling, jetty cross-bracing,
landing steps, reatining wall, etc.)
>