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Fig. 17: Lay-up of plywood

1: 3-ply plywood 2: 5-ply plywood 3: Wood-based core plywood

Plywood

Plywood is made from at least three cross-banded plies (i.e. grain of adjacent plies at approx. 90° to each other). The plies are glued together with waterproof phenolic resin glue with the help of pressure and heat. After pressing, the edges are trimmed and the surface(s) sanded or otherwise processed. Plywood can also be moulded into virtually any shape by applying pressure, heat and moisture (moulded plywood).

Plywood is suitable for many applications. For example, it can be used as a bracing facade cladding, as roof decking, as wall sheathing or in interior fitting-out work.

Plywood absorbs moisture and swells in the plane of the board as well as in its thickness. If the material is left untreated, ultraviolet r adiation and driving r ain will turn it a grey colour, which can be very irregular on the side exposed to the weather in particular. A facade of plywood can be protected by a coat of diffusion-permeable, water-repellent paint. The edges especially must be sealed with a good-quality water-repellent paint.

Veneer plywood

Veneer plywood is manufactured from several cross-banded veneer plies (i.e. thin sheets produced by a rotary cutting, slicing or sawing) pressed together. In comparison to other wood-based products, this material is ideal for loadbearing constructions because it's very high modulus of elasticity and high strength make it suitable for situations with high stresses.

Wood-based core plywood

This is a type of plywood with a central core of timber strips, known as blockboard, laminboard or battenboard depending on the width of the strips used.

Multi-ply boards

Plywood with at least five cross-banded plies and a ply thickness of 0.8-2.5 mm is often known as multi-ply board. Multi-ply boards can be used for external cladding, even in severe weather conditions, or internal linings. The high load-carrying capacity of such boards makes them suitable for loadbearing applications as well.

Fig. 18: Close-up of edges of multi-ply boards

are primarily used as loadbearing and bracing sheathing in timber buildings, and as formwork for concrete.

Solid timber panels

Three or more cross-banded layers of strips without any outer sheathing. These can be used as loadbearing plates, but must be protected from the weather.

Fig. 19: Surface (sliced) and edges of 3- and 5-ply core plywood

In contrast to peeled veneers, the production of sliced veneers involves cutting the trunk into thin sheets.

Fig. 19: Surface (sliced) and edges of 3- and 5-ply core plywood

In contrast to peeled veneers, the production of sliced veneers involves cutting the trunk into thin sheets.

Fig. 17: Lay-up of plywood

1: 3-ply plywood 2: 5-ply plywood 3: Wood-based core plywood

3- and 5-ply core plywood

A 3- or 5-ply core plywood consists of cross-banded plies with thicknesses between 4 and 50 mm. These boards

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