Plywood facts include information about the different types of face veneers, the glue lines that are available for different applications, available preservative treatment, emissions emitted from the ply and the preservative treatment available for plywood:
Plywood Specifications – Face Veneers
A Grade Veneers
An appearance grade face veneer with no visible defects making it suitable for “clear finishing”. Where surface decorative appearance is a primary consideration, this appearance grade quality should be specified. This includes Austral Premium Ply & Marine Ply.
To read more, please visit A Veneer (Australian Standards)
B Grade Veneers
An appearance grade face veneer suitable for high quality paint finishing and is not generally suitable for clear finishing. Where a high quality paint finish is a primary consideration, this face veneer quality should be specified. This includes Austral Premium Plywood, Birch Plywood & Hardwood Plywood.
To read more, please visit B Veneer (Australian Standards)
C Grade Veneers
A non-appearance grade face veneer with a solid surface in which all open defects such as holes, knots or splits are filled. For applications requiring a solid non-decorative surface, this face veneer quality is designed specifically for this purpose, such as ply flooring which is to be overlaid with a decorative flooring surface. This includes Austral Premium Plywood, Birch Plywood, Flooring, Hardwood Plywood and Structural & Non-Structural Plywood.
D Grade Veneers
A non-appearance grade face veneer in which open imperfections are permitted. For structural and non-structural applications where decorative appearance is not a requirement, this face veneer should be specified. A limited number of knots and knot holes up to 75mm wide are permitted within this veneer specification. This includes Flooring, Hardwood Plywood and Structural & Non-Structural Plywood.
To read more, please visit the EWPAA Website Facts About Plywood and LVL
Plywood Specifications – Gluelines
Type A Bond
Produced from a Phenol Formaldehyde (PF) resin, which sets permanently under controlled heat and pressure. This forms to create a permanent bond that will not deteriorate under wet conditions, cold or heat. This bond is recognisable by its distinct black colour.
Type A bond is specified in AS/NZS 2272 for marine plywood, AS/NZS 2271 for exterior plywood used under conditions of long term full exposure or under wet or damp conditions.
Type B Bond
Produced from Melamine Fortified Urea Formaldehyde (MUF) resin, which sets permanently under controlled heat and pressure. The exterior plywood standard includes Type B bond and is suitable for application involving concrete formwork plywood that is stamped with the EWPAA Approved B bond stamp.
Type C & D Bonds
Both the C and D bond glue lines are both interior bonds. Type A bonded plywood should be used for areas of doubtful moisture conditions, such as areas around vanity units, sinks, and laundry tubs.
Produced for exterior use with a phenolic resin adhesive.
To read more, please visit the EWPAA Website Facts About Plywood and LVL
Plywood Specifications – Preservative Treatment
Preservative Treated Plywood
Plywood may be required to resist attack under certain conditions as listed in the below table.
For protection against these attacks, the correct preservative treatment is essential for all types of plywood, whether they are painted or unpainted, that will be permanently exposed to the weather.
The two types of treatment being Veneer Treated as distinct from Envelope Treated.
Veneer Treated – ACQ
Treatment applied via the impregnation of the veneers. Therefore making it a superior method so that cut panels still retain their preservative properties.
ACQ treatment is available in Pine Plywood and Hardwood Plywood. Standard sheet sizes are 2400mm x 1200mm in: 12mm, 15, 17 & 19mm. Other thicknesses are available upon request, contact us for more information.
Envelope Treated – LOSP
Pressure treating the plywood, specifically the outer veneers, ends of the sheets and edges. In comparison to the ACQ treatment, the LOSP treatment may not penetrate through the glue lines to the middle veneers. When cut, LOSP treatment must be re-applied to the cut edge.
LOSP treatment is available in Pine Plywood and Hardwood Plywood. Standard sheet sizes are 2400mm x 1200mm: 12mm, 15, 17 & 19mm. Other thicknesses are available upon request, contact us for more information.
|Hazard Class||Exposure||Resist Attack||Specific Service Conditions|
|H1||Inside, above ground||Lyctid borers||Completely protected from the weather and well ventilated, and protected from termites|
|H2||Inside, above ground||Borers & termites||Protected from wetting and with no leaching|
|H3||Outside, above ground||Borers, termites & moderate decay||Subject to periodic moderate wetting and some leaching|
The Hazard Classes are further defined and described in the AS/NZS1604.
To read more, please visit the Forest & Wood Products Australia website Guide to the specification, installation and use of preservative treated engineered wood products.
Plywood Specifications – Core Gaps
Consists of a solid full grade cores throughout the ply with no core gaps.
Exterior/ Structural Ply
Minimal core gaps in the laying up of the inner plies ensuring the maximum potential in attaining the full strength potential across the entire panel for the structural ply.
Minimal core gaps.
To see an example of common core gaps, please visit the Austral Plywood website Core Gaps.
Plywood Specifications – Emissions
All information within the following “Emissions” section is gathered from EWPAA: Technical Note, Formaldehyde Emissions from Plywood and Laminated Veneer Lumber.
This section refers to on-going industry wide testing of formaldehyde emissions from EWPAA branded products, summarising the survey completed by the EWPAA that emissions from Type A Bonded products, with phenolic adhesives, represent over 90% of EWPAA production which have effectively zero emissions.
Formaldehyde is a colourless, strong smelling gas that occurs naturally within the environment and is emitted by processes such as decay, combustion and naturally by all timber species.
Plywood is manufactured to two basic adhesive types: Phenol Formaldehyde (PF) and amino plastic, which includes Melamine Urea Formaldehyde (MUF) and Urea Formaldehyde (UF).
There are vast differences in the chemistry between the two types of adhesives. With PF bonded products, after any low level residual formaldehyde from the manufacturing process has dissipated within a few days, they do not emit formaldehyde.
PF adhesive, being identifiable by its black colour, is called Type A under the Australian and New Zealand ply standards as is used in the manufacture of structural plywood, marine plywood exterior (Type A) products.
In both Europe and the United States, products that are bonded with PF adhesives are classified as non-emitting and are exempt from formaldehyde emission regulations.
Amino plastic bonded products tend to have higher residual free formaldehyde levels and can emit low levels of formaldehyde.
Technical Note Conclusion
Formaldehyde emissions from EWPAA certified products are well below acceptable exposure limits specified by Workplace Australia and do not constitute a health risk.
The formaldehyde emission classes in the Australian/ New Zealand Standards are details in the below table. Products labelled with emission classes E0 and E1 have extremely low formaldehyde emissions.
|Emission Class||Formaldehyde Emission Limit (mg/l)||Formaldehyde Emission Limit (ppm)*|
|Super E0||Less than or equal to 0.3||Less than or equal to 0.024|
|E0||Less than or equal to 0.5||Less than or equal to 0.04|
|E1||Less than or equal to 1.0||Less than or equal to 0.08|