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Timber Treatment
Why and How?
Presenter: Steven Koch
Arch Wood Protection
TABMA Breakfast 28st Oct 2008.
Why treat timber ?
• Timber is perishable.
• Extend the life of durable and non-durable timbers against
biological agents and decay.
• Utilise renewable plantation timbers and conserve old
growth forests.
• Plantation timbers faster grown with a greater proportion
of sapwood present.
• Reliability and proven service life.
• Means that wood can be used as an alternative to more
energy and resource intensive materials in many
situations.
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Brief History
• Pressure treatment developed in England in
1838
• CCA developed in India (1933)
• CCA used in Australia since 1957
• 1980’s LOSP and Copper based
preservatives developed in response to
environmental legislation.
TABMA Breakfast 28st Oct 2008.
Basic Wood Characteristics
Density and strength
virtually identical
SAPWOOD
Living tissue
Light colour
Easy to treat
HEARTWOOD
Non-durable
Non-living tissue
Effect of
saw cut
Darker colour
Difficult to treat
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More durable
2
Softwood Structure
Sapwood
Late wood
Heartwood
Early wood
Transition Wood
Rays
Pith
Outer
Bark
Inner
Bark
Tangential
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Radial
Cambium
Cells
Bordered Pits
Rays
Late wood
Early wood
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Vessels
Hardwood
Structure
Rays
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Enemies of Wood
Fungal Decay
Stain
Wood
Boring
Insects
Termites
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CSIRO Termite Activity Survey
H2
H2F
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Natural Durability
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Natural Durability
• The sapwood of ALL species is considered
NON DURABLE.
• Heartwood can be classified according to its
natural durability against wood destroying
organisms.
• CCA treated Radiata Pine sapwood performs
BETTER than Class 1 Natural Durability
timbers.
• CSIRO have conducted an in-ground study on
Natural Durability for over 31 years.
TABMA Breakfast 28st Oct 2008.
Natural Durability
Class 1
Timbers of the highest natural durability
which may be expected to resist both
decay and termite attack for
at least 25 years and up to 50 years
Grey Box, Grey Ironbark,
Red Ironbark, Yellow Box,
Yellow Gum, Tallowwood
Class 2
Timbers of high natural durability which
may be expected to have a life of
about 15 to 25 years.
Jarrah, River Red Gum,
White Mahogany, Yellow
Stringybark, Red Box
Spotted Gum, White Cypress Pine
Class 3
Timbers of moderate durability which
may be expected to have a life of
about 8 to 15 years
Broad-leaved Peppermint
Southern Blue Gum
Sydney Blue Gum
Brush Box, Manna Gum
Candle bark
Timber of low durability which may last
about 1 to 8 years.
These timbers have about the same
durability as untreated sapwood, which
is generally regarded as Class 4,
irrespective of species.
Mountain Ash
Douglas Fir (Oregon)
Radiata Pine
Western Red Cedar
Hoop pine
Slash Pine
Class 4
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Regulatory Structure
• Wood preservatives fall within scope of APVMA
regulated chemicals.
• AS1604 provides national structure for approval
process, preservative and wood treatment
specifications (not a primary standard under BCA).
• State legislation in Qld and NSW (TUMA, TMA
respectively).
• Treatment plant sites fall under state EPA licensing
requirements.
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Hazard Classes
HAZARD CLASSES 1 & 2
HAZARD CLASS 3
HAZARD CLASSES 3 & 4
HAZARD CLASS 5/6
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Hazard Classes as per AS1604
Hazard
Level
Application
Situation
Biological Hazard
H1
Dry, protected
Beetle borers only
H2 &
H2F
Dry, protected
Termites and borers
H3
Exterior, above ground
Moderate decay and termites
H4
Exterior, ground contact
Severe decay and termites
H5
Exterior, critical ground
contact or PFW contact
Severe decay and termites
H6
Marine water contact
Marine borers
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AS1604 - Penetration
Hazard
Durability
Sapwood
Heartwood
H1
1 and 2
100%
Not Required
H2
1 and 2
Not Required
3 and 4
100%
5 mm (<35) 8 mm (>35) Envelope* on non termite
resistant species
H2F
1 and 2
Not Required
3 and 4
5mm
envelope
H3
1 and 2
100%
H4
1 and 2
H5
1 and 2
H6
1 and 2
3 and 4
5 mm on non termite resistant species
Not Required
5 mm (<35) 8 mm (>35) Envelope*
3 and 4
100%
Not Required
10 mm Envelope*
3 and 4
100%
Not Required
20 mm Envelope*
3 and 4
100%
Not Required
20 mm Envelope*
3 and 4
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Penetration Clause
Okay
Meets the previous criteria.
Fail
Extends more than halfway through the piece.
Fail
Exceeds 50% of the width of the piece.
Fail
Fails all three criteria.
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Full Penetration Requirement on D1&2 Timber and
Termite resistant heartwood (Slash Pine)
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Full Penetration Requirement on D3&4 Timber and
Non-termite resistant heartwood.
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Envelope Penetration Requirement for envelope
Slash Pine
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Envelope Penetration Requirement on Radiata Pine
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Quarter Sawn
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Penetration Problems
• Most common causes of penetration
failure
– High moisture content.
– Impenetrable heartwood.
– Quarter sawn timber.
• Penetration is achieved by pressure.
– Time at pressure.
– Depth of pressure.
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Cutting Patterns
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Treatment Penetration Patterns
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Preservatives Used
• Boron salts (H1 only)
• LOSP (TBTN, Azoles, copper naph, permethrin,) (H1,H2, H3)
LOSP Products
• Dip Applications (permethrin,) (H2F) Oil based Includes T2
Blue (Tanalith T 5mm envelope)
• Spray Applications (Bifenthrin) (H2F) Water based 2mm
envelope
• CCA (type C) (H1 to H6)
• Copper based (Tan E, ACQ) (H3 – H5)
• Creosote oil (H3 – H5)
• Glue line additives and veneer treatments (Engineered Wood
Products) (H2, H3?)
• Remedial (Blue Stain Control, Coatings, CN oil/Emulsions, etc.)
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Oil based Treated Pine benefits
Very suitable for a “dry after treatment”, above ground
market (H1, H2, H3), with Engineered Wood Products
and re-manufactured wood products.
Dry-after-treatment process
No re-drying required
Non-corrosive to metals, be aware of painting
procedures
Just-in- time supply, stock held untreated can be
converted on the way to market
Structural grading is not effected
Dimensional stability
Coloured treatment for easy identification
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Application Methods
Envelopes
Envelopes
Dipping/Coating
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Vacuum / Pressure Plant
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TIMBER TREATMENT
PROCESS
Vacuum
Pump
PRESSURE VESSEL
Pressure
Pump
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Vacuum/Pressure Impregnation
1
2
Vessel flooded under
vacuum, release of which
then forces preservative
into the wood. Low
pressure may be applied for
more resistant timber or to
achieve a higher
specification.
Vacuum
created and
timber cells
evacuated
of air.
Vacuum
held.
3
4
Second
vacuum
applied to
evacuate
timber cells of
preservative.
Surface wet.
Venting to atmospheric
pressure drives surface
preservative back into
timber. Surface drip dry.
TABMA Breakfast 28st Oct 2008.
Treated Timber Branding
049 70 H2
Plant Number –
Identifies
producer / treater
Preservative
Number – Identifies
preservative
Hazard Level –
Identifies
correct use type
AS1604TABMA
REQUIRES
BRANDING
Breakfast 28 Oct 2008.
st
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NEED FOR MORE
SAFE HANDLING
& CONSUMER
INFORMATION AT
POINT OF SALE
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The End
Thank you
Questions?
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