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The strongest, lightest, most versatile utility and decorative product made from a renewable resource, plywood is kilo for kilo stronger than steel. Plywood was the first type of engineered wood to be invented. It is made from thin sheets of wood veneer, called plies or veneers. These are stacked together with the direction of each ply’s grain differing from its neighbours’ by 90° (cross banding). The plies are bonded under heat and pressure with strong adhesives, usually phenol formaldehyde resin, making plywood a type of composite material. Laminating an odd number of plies (3, 5, 7…) reduces warping while increasing the number of plies increases the resistance to shearing forces. A common reason for using plywood instead of plain wood is its resistance to cracking, shrinkage, twisting/warping, and its general high degree of strength.
BENEFITS OF PLYWOOD
Renewable Resource – A natural product from a renewable resource.
Beautiful – Preferred because of its warmth and natural markings.
Strength – Unique cross-layered structure makes it kilo for kilo, stronger than steel.
Efficiency – Uses more of the log than timber.
Versatility – Can be bent and formed to meet various sizes and shapes.
Durability – Long-lasting and good resistance to damage.
TYPES OF PLYWOOD
Plywood can be broadly classed as either ‘Exterior’ plywood or ‘Interior’ plywood. Veneer quality, glue type and timber species are the major contributing factors that determine the application of a plywood panel.
Plywood is classified according to grades, which are based on face and back veneer quality. The Plywood Association of Australia (PAA) grading standards are as specified in the following table.
|Grade A||Grade S||Grade B||Grade C||Grade D||Grade PG|
|A high quality appearance grade veneer suitable for clear finishing.||An appearance grade veneer which permits natural characteristics such as knots as a decorative feature subject to agreement.||An appearance grade suitable for high quality paint finishing.||A non-appearance grade with a solid surface. All imperfections such as knot holes or splits are filled.||A non-appearance grade with permitted open imperfections. Limited number of knots and knot holes up to 75mm wide are permitted.||A non-appearance grade that has open imperfections such as holes, knots, splits and rough grain.|
|Textured exterior cladding
Interior wall lining
Interior ceiling lining
Furniture & joinery
Interior wall lining
Interior ceiling lining
|Furniture & joinery
Gussets Roof decking
Flooring Sub sheathing
Bins, boxes & crates
Stressed skin panels
Beams & portals
Pallets Fillets & liners
Most local plywood conforms to the PAA standard with imported plywood in compliance with other grading standards such as:
BB/CC grade which conforms to the Japan Plywood Inspection Corporation (JPIC) standard. BB/CC grade plywood has a good face that may have small
imperfections that are filled and sanded. ‘CC’ back may have rough patches and filled splits.
Overlay and Better (OVL/BTR) is more of an appearance grade plywood that conforms to the International Hardwood Product Association (IHPA) that uses
more veneer in construction to produce higher stress grade plywood.
Glues used to bond veneers together are an element that influences the application of the plywood. Common glues are as follows:
‘A Bond’ (WBP) – a waterproof glue line produced from phenolic resins (WBP -Water Boil Proof adhesive) that will not deteriorate under extreme conditions. It is readily recognisable by its black colour. Type A bond is specified in AS/NZS 2272, 2269 and 2271 for marine, structural and exterior Plywood.
‘B Bond’ – produced from melamine fortified urea formaldehyde resin and suitable for limited exposure.
‘C&D Bond’ – is produced from urea formaldehyde resin and suitable for interior use only.
Structural Plywood manufactured to AS/NZS 2269 Plywood – Structural is suitable for use in all permanent structural applications. A permanent Type A phenolic resin is used to bond the individual timber veneers. The Type A bond is distinctly dark in colour and is durable and permanent under conditions of full weather exposure, long term stress and combinations of exposure and stress.
Structural plywood is manufactured from a range of softwood and hardwood timber species. These timber species may not be durable when used in weather exposed situations. In exposed applications, structural plywood must be preservative treated to ensure it lasts its full service life and surface finished to minimise surface checking.
PAA branded structural plywood is manufactured under a rigorous product quality control and product certification system ensuring a quality controlled engineered panel of known and consistent physical and mechanical properties.
For assured performance, structural plywood should be branded with the ‘PAA Tested’ stamp.
The engineering properties of structural plywood are tabulated in both AS/NZS 2269 and AS1720.1. Structural plywood engineering properties are given for eight standard stress grades, F7, F8, F11, F14, F22, F27 & F34.
Click below to find out more or contact us on: John Carroll 0414301515 and Colin Carroll 0421273887 Email for a price or more information: John@carrollswholesale.com, Colin@carrollswholesale.com