Different woods

There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. For every tree species there is a range of density for the wood it yields. There is a rough correlation between density of a wood and its strength (mechanical properties). For example, while mahogany is a medium-dense hardwood which is excellent for fine furniture crafting, balsa is light, making it useful for model building. The densest wood may be black ironwood.

It is common to classify wood as either softwood or hardwood. The wood from conifers (e.g. pine) is called softwood, and the wood from dicotyledons (usually broad-leaved trees, e.g. oak) is called hardwood. These names are a bit misleading, as hardwoods are not necessarily hard, and softwoods are not necessarily soft. The well-known balsa (a hardwood) is actually softer than any commercial softwood. Conversely, some softwoods (e.g. yew) are harder than most hardwoods.

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Oriented strand board

Oriented strand board, or OSB, or waferboard, or Sterling board (UK) or SmartPly (UK & Ireland) is an engineered wood product formed by layering strands (flakes) of wood in specific orientations. In appearance it may have a rough and variegated surface with the individual strips (around 2.5 by 15 cm (approx. 1 in by 6 in) each) lying unevenly across each other.

Different qualities in terms of thickness, panel size, strength, and rigidity can be imparted to the OSB by changes in the manufacturing process. OSB panels have no internal gaps or voids, and are water-resistant, although they do require additional membranes to achieve impermeability to water and are not recommended for exterior use. The finished product has similar properties to plywood, but is uniform and cheaper. It has replaced plywood in many environments, especially the North American structural panel market. The most common uses are as sheathing in walls, floors, and roofs.

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Engineered wood

Engineered wood, also called composite wood, man-made wood includes a range of derivative wood products which are manufactured by binding together the strands, particles, fibers, or veneers of wood, together with adhesives, to form composite materials. These products are engineered to precise design specifications which are tested to meet national or international standards. Plywood is sometimes called the original engineered wood.

Typically, engineered wood products are made from the same hardwoods and softwoods used to manufacture lumber. Sawmill scraps and other wood waste can be used for engineered wood composed of wood particles or fibers, but whole logs are usually used for veneers, such as plywood. Alternatively, it is also possible to manufacture similar engineered cellulosic products from other lignin-containing materials such as rye straw, wheat straw, rice straw, hemp stalks, kenaf stalks, or sugar cane residue, in which case they contain no actual wood but rather vegetable fibers.

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Engineered wood types

• I-joist
• Glued laminated timber
• Multilaminar veneer
• Veneer-based
            o Plywood
            o Laminated veneer lumber (LVL)
            o Parallel strand lumber (PSL)
            o Stamina wood
            o Parallam
• Parallel strand lumber

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Engineered wood characteristics

Engineered wood products are used in a variety of ways, often in applications similar to solid wood products. Engineered wood products may be preferred over solid wood in some applications due to certain comparative advantages:

• Because engineered wood is man-made, it can be designed to meet application-specific performance requirements.
• Large panels of engineered wood may be manufactured from fibres from small diameter trees.
• Small pieces of wood, and wood that has defects, can be used in many engineered wood products, especially particle and fiber-based boards.
• Engineered wood products are often stronger and less prone to humidity-induced warping than equivalent solid woods, although most particle and fiber-based boards readily soak up water unless they are treated with sealant or paint.

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