Plywood – The only engineered wood panel
Product Certified ‘PAA Plywood’ is kilo for kilo stronger than steel and therefore is the answer.
There are two major types of plywood manufactured under the ‘Plywood Association of Australian (PAA) Quality Control Program’.
1. Exterior ‘waterproof glued’ Plywood
2. Interior Plywoods
As over 70% of the PAA plywood sold is of an exterior type we shall examine in detail the different varieties available and their characteristics and uses. A short note on interior plywoods will follow.
The single most important element that controls where plywood can be used in the type of glue used in manufacture.
Australian Standards specify tests for four types of gluebond: Types A, B, C, and D.
- A-BOND – produced from a phenol formaldehyde (PF) resin and forms a permanent glueline that will not deteriorate under wet conditions, heat or cold e.g. used in the manufacture of Marine and Structural plywoods.
- B-BOND – produced from melamine fortified urea formaldehyde resin (MUF) resin and is suitable only for limited exposure e.g. formply, door skins.
- C & D BOND – produced from urea formaldehyde (UF) resin are both for interior use only, and should not be used in structural applications or wet or damp areas
Exterior ‘Waterproof Glued’ Plywoods
There are 4 major varieties of Exterior ‘Waterproof glued’ Plywood manufactured under PAA Quality Control to Australian Standards.
Marine ‘the Rolls Royce of Plywoods’, manufactured to AS/NZS2272-Type A Bond. It is manufactured from selected species with a minimum stress grade F14. Marine plywood possesses A grade faces both sides and is sanded both sides.
N.B. Imported “MARINE” plywood made to overseas standards should be treated with caution and NOT substituted for AS/NZS 2272.
Structural Plywood Manufactured to AS/NZS 2269 Type A Bond is the only wood based panel that can be considered an engineering material as it is the ONLY wood panel that possesses defined, standardised structural properties.
By far the biggest selling Exterior “Waterproof glued’ Plywood in Australia is manufactured mainly from plantation softwood veneers such as radiate, hoop and slash pine. This plywood is designed for a structural rather than aesthetic function and is normally available in 2 grades based on face and back veneer quality.
C D Grade
C grade face which is basically a solid surface which can include minor defects, filled or patched; D grade back which can contain open defects such as knot holes or splits;
D D Grade
Both face and back may contain open defects as mentioned above.
N.B. special types of structural plywood can be manufactured using A, B or S quality faces to order.
Exterior Plywood Manufactured to AS/NZS 2271 either Type A or Type B Bond (see not on gluebonds).
Exterior Plywood is a non-structural plywood suitable for hoardings, signs and cladding where a high quality aesthetic finish is required. Two standard face grades are produced:
- A Grade for clear finishing
- B Grade for painting
Normal grades available are A D & B D with special grades made to order.
Concrete Form Plywood, basically formply is a plywood with a “Plastic” or phenolic impregnated paper overlay to give excellent off form finishes and multiple re-uses. Edges are also usually sealed. (For full details ee PAA manual Plywood in Concrete Formwork). Formply is normally manufactured in 4 stress grades ranging from F11 to F22 in 3 gluelines Type A, Type B and even Type C (INTERIOR). So care must be taken to specify the right type for the right job. E.g. It would be foolish to use a Type C bonded formply where long term exposure to the elements would apply.
N.B. Formply is NOT Marine Plywood.
Engineered Wood Products (EW)
EWP such as Laminated Veneer Lumber (LVL) manufactured to AS/NZS 4357 is also available. Contact the PAA for detailed information.
Interior Grade plywood manufactured to AS/NZS 2270 has either Type C or Type D bond. Type C bond should be used in internal areas of high humidity such as bathrooms and Type D bond is usually satisfactory for interior application under normal conditions of humidity. Interior plywood MUST NOT be used in fully exposed wet or damp or permanent structural applications. Standard face grades are as for Exterior Plywood AS/NZS 2271.
Apart from the biggest selling types of plywood mentioned previously there are a number of Specialty Plywoods available for particular purposes.
- Large sized scarf jointed panels – Boats, tructs, railcars and signs
- Medium density overlaid plywood – Signs, cladding
- Metal face plywood – Architectural applications
- Lead cored plywood – X-Ray rooms
- Cutting forms – Printing industry
- Fibreglass overlaid plywood – Containers, chemical storage
- Preservative treated plywood – Treatment against insect and fungal attack, external cladding
- Anti-slip overlaid plywood – Bridges, pedestrian walkways
- Fire retardant plywood – Refer AS1530
- Perforated plywood – Acoustic applications
- Decorative paper overlaid plywood – Caravans, wall panelling
- Super thin marine & aircraft plywood – Model aircraft boats etc
- Moulded plywood – Curved ceiling panels, furniture fitments
- Grooved feature panels – Wall/ceiling linings
Full information on all the aforementioned is available from the PAA.
Weights of Plywood varies dependant on the species, however, as a guide approximate weight of 2400 x 1200mm radiate pine structural plywood panels are as follows:
- Internal – standard paints and clear finishes should be used in accordance with the manufacturers instructions.
- External – exhaustive tests carried out by the PAA indicate that for best results only high quality 100% acrylic paint systems should be used externally.
N.B. also use only light reflective colours such as White and do not use dark colours such as Mission Brown or Black.
- For guaranteed long term performance in full exterior applications, such as exterior cladding, it is imperative that the plywood be rot-proofed.
Because plywood is a wood based panel no special tools are required apart from the normal woodworking variety.