Wood has long been used as a construction material and revered for its strength and natural aesthetics. But with forests being chopped down across the globe to meet our insatiable demands, it’s time to look towards an alternative solution and wood composite may be the answer.
What is wood composite?
Wood composites include a range of different derivative wood products, all of which are created by binding the strands, fibers or boards of wood together. It’s also known as manmade wood, manufactured board or engineered wood, as well as wood-plastic composite (WPC) when using wood fibers and thermoplastics. Similar composite products can also be made from vegetable fibers using lignin-containing materials such as hemp stalks, sugar cane residue, rye and wheat straw, with chemical additives enabling the integration of polymer and wood flour while helping facilitate optimal processing conditions.
They are fixed using adhesives and are engineered to certain specifications, resulting in a material that can have diverse applications. But the best part about wood composites is that they can be created using wood waste materials and smaller trees, reducing the need to fell old-growth forests.
How is wood composite made?
Wood composite is usually made from the same hardwoods and softwoods used for lumber, except using the sawmill’s scraps and wood waste, and created by mixing ground wood particles with heated thermoplastic resin. Some combine and process the materials into pellets which are re-melted and formed into the final shape, while others create the final product by a one-step mixing and extrusion process.
Both virgin and recycled thermoplastics are used, with polyethylene-based products the most common. UV stabilizers, colorants, coupling agents and lubricants can also be added to create a product specifically targeted to its application, with both solid and hollow shapes formed.
Use of wood composite products
Composite wood products can be used in a variety of different ways, including both home and industrial construction, and is often used to replace steel for joists and beams in building projects. Their most widespread use, however, is in outdoor deck flooring, but they are also popular for railings, fencing, benches, window and door frames, cladding and landscaping work.
While composite wood can be used in most applications traditionally using solid wood, it is also a popular material for making flat-pack furniture due to its low manufacturing costs and light weight properties.
Types of wood composite products
If you are visiting your own hardware store, then what composite wood materials might you find? Plywood is considered the original composite wood product, manufactured from sheets of cross-laminated veneer which are bonded with moisture-resistant adhesives under heat. Fiberboard is another, made by combining wood fibers with wax and a resin binder under high temperatures and pressure, while particle board is manufactured from wood chips or sawmill shavings pressed with a synthetic resin.
Oriented strand board is made from strands of wood arranged in layers and bonded together using moisture-resistant adhesives. These are then cross-oriented to give the panel strength and stiffness. Laminated timber is created using dimensional timber glued together into structural columns or beams, while laminated veneers bond thin wooden veneers into a large billet which can be used for rafters, beams, columns and joints.
Advantages of wood composite
One of the main advantages of wood composite is that because it is man-made, it can be designed for specific qualities or performance requirements. It can be made into different thicknesses, grades, sizes and exposure durabilities, as well as manufactured to take advantage of the natural strength characteristics of wood (and sometimes results in a greater structural strength and stability than regular wood).
As a result, it can be used in a diverse array of applications, from industrial scale to small home projects, and enable more design options without sacrificing structural requirements.
Composite wood is also easy to work with using regular tools and can be efficiently cut, fastened and drilled using basic skills. It is easily malleable and can be molded into almost any desired shape. Plywood, for example, can be easily bent to create a curved surface, without compromising its strength. It can also be manufactured into large panel sizes meaning that builders don’t have to install numerous smaller pieces.
Composite wood is also less likely to fade or warp over time and far more resistant to rot, decay and marine borer attack than solid wood. It means you don’t have to put as much energy or money into maintaining it over time, reducing the overall costs of the material. Wood composites also tend to be cheaper than high-quality solid wood due to the affordability of wood scrap material and the manufacturing process.
It can be manufactured in a variety of colors, eliminating the need for paint, and with a comparable appearance and feel to timber. You can choose the style that suits exactly what you want, often with wind and UV resistant properties.
But one of the main advantages of composite wood is its environmental impact, as it can be produced from smaller trees when compared to solid lumber and doesn’t require the felling of large, old-growth forests. It can also be made from wood that has defects and would otherwise be discarded, as well as species that have not traditionally been used for solid wood.
But its environmental impact depends largely on the ratio of renewable to non-renewable materials used in its construction, with petroleum-based polymers having a negative impact because of their reliance on non-renewable raw materials.
Disadvantages of wood composite
Despite its environmental advantages, some wood composite does require more primary energy for its manufacture when compared to solid lumber. Some particle and fiber-based composite woods are also not suitable for outdoor use as they can absorb water and be more prone to humidity-induced warping than solid woods.
Another concern regarding wood composites is the adhesives used in their design with some resins releasing toxic formaldehyde in the finished product (particularly those made with urea-formaldehyde bonded products which is one of the cheapest and most common adhesives). The plastic materials often used in the creation of wood composites also have a higher fire hazard when compared to solid wood products, due to their higher chemical heat content and melting properties.
Consumers should keep in mind that not all wood composites are created equal (with different materials and ratios) and you do get what you pay for. It’s better to invest in a high-quality composite material that will endure the elements over time and recreate the natural warmth of solid wood than a cheap alternative.
The future of wood composites
The ability of wood composites to be tailored to specific uses, together with their strength properties and affordability, makes them a viable solution to reducing the need for solid wood. They have been successfully applied in all forms of building, from small home projects to industrial construction work, and as technology surrounding their manufacture only advances, the future looks bright.