Multiplex board

Multiplex board normally refers to a specific type of plywood product which is of at least five layers of veneer or ply of the same thickness, ranging from 0.8 – 2.5 mm thick. The timber used for these types of plywood tend to be single or multiple species beech, maple, birch or spruce, overall thicknesses can range from 4mm to 150mm, with thicker products tending to have better fire ratings. Depending on the glues used, class and grade it can be used internally or externally.

[edit] Manufacturing

The manufacturing process is the same as plywood, being prepared by steaming or dipping in hot water. It is then peeled into thin plies of between 0.25-2 mm by a lathe machine. It is then formed into large sheets.

The sheets consists of the face (the surface that is visible after installation), the back, and the core (which lies between the face and the back). The plies are glued together normally using a strong adhesive, usually a phenol or urea formaldehyde resin, however increasingly different products might be available that use alternative natural polymer glues with reduced environmental impacts.

Each layer of ply is oriented with its wood grain perpendicular to the adjacent layer, rotated up to 90-degrees to one another. This is called ‘cross-graining’ and it is this that distinguishes plywood from laminated veneer lumber (LVL). In LVL, the direction of the plies is the same, whereas in plywood, the direction of the plies alternates. It is usual to have an odd number of plies so that the sheet is balanced and this helps to reduce warping.

Cross-graining reduces the tendency of the plywood to split when nailed at the edges. It also reduces expansion and shrinkage, which improves its dimensional stability, and it gives panels consistent strength in all directions. The higher number of layers that make up multiplex compared to standard plywood helps improve it structural strength, durability and integrity. The durability of the face and back veneers can be improved by the addition of a thin outer layer that resists moisture, abrasion and corrosion, as well as making it easier to apply paint and dye. Some of the materials that can be used include plastic, resin-impregnated paper, fabric, Formica, and metal.

[edit] Uses

Multiplex has many of the uses of standard plywood, where strength and durability is required such as furniture, cladding and flooring, because of its extra strength it tends to be used where it needs to carry its own weight with out bowing, such as kitchen worktops, bars or special furniture featuring some element of cantilever.

The considerable strength and durability of multiplex means it can also be used to create structural elements such as box beams, I beams and Z beams, as well as in structural floor, roof and wall elements as sheets for its racking capabilities.

Multiplex also has some improved resistance to heat and as such might be specified around for example kitchen hobs and ovens. It is also often used as a flooring material in the automobile industry with a facing material because of its hard wearing heat heat resistant qualities. Depending on the glue used to bind the various ply layers, it may also be used externally, normally with a final protective layer such as a rain-screen.

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• Laminated veneer lumber LVL.
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• Medium density fibreboard - MDF
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• Oriented strand board.
• Panelling.
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