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Composite Lumber

Until the 1990s, wood was the material of choice for deck construction. However, new products, composites, began to emerge at this time. These new products offered the look and workability of wood, but they were more water resistant and required less maintenance. Over time, these lower maintenance decking options increased in popularity. Although the majority of decks are still built of pressure treated pine, redwood, cedar or mahogany, use of composite woods has increased as outdoor decks and living areas have become popular as home features.

Working with composite lumber is similar to working with wood. However, composite lumber has the added benefit of being less likely to split or delaminate. Some composite lumber is also engineered to be lighter weight for easier handling. Composite lumber is also more stain, scratch, and mold resistant, and is therefore supposed to have a longer life than wood lumber

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.

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.

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.

What Is a Composite Decking Board Made Of?

Equal parts of wood fiber and plastic are mixed with pigments, ultraviolet inhibitors, and borate preservatives, then usually heated and extruded. The texture, if any, is embossed onto the warm surface before it cools.

Waste Wood: Ground-up wood from mills and furniture factories

Recycled Plastic: Shredded polyethylene from milk jugs and shopping bags

Pros & Cons of Composite Decking

Before you make a commitment, weigh the pros and cons of composites.

PROS:

Reduced maintenance: Forget about having to bleach and stain wood every other year. With the money you save by not using these coatings and cleaning materials, you can recoup the higher cost of composites in about five years.

Long life: Composites don’t rot or attract termites, they can’t warp or check, and you can go barefoot without fear of splinters.

Minimal fading: All composites turn a slightly lighter shade after the first two or three months in the sun, then the fading stops. (Left to its own devices, wood inexorably turns gray.)

Longer boards: Up to 20 feet, which means fewer end joints.

High recycled content: Every 10 square feet contains nearly 3,000 recycled plastic shopping bags and 1,100 one-gallon milk jugs.

CONS:

High initial cost: Low-end composites are priced about 30 percent higher than pressure-treated pine. High-end composites run about the same as ipe (ee-PAY), a hardwood decking harvested from tropical rain forests.
Easily scuffed: Moving furniture, frisky dogs, and gritty shoes will abrade new composites. Light scratches can’t be sanded out but do blend in over time.

Prone to staining: The wood fibers are easily stained by food and grease. And the hardwood in many mixes can create uneven brownish tannin stains early on when wet, but they typically disappear over time.

Hot underfoot: Like dark hardwoods, dark composites heat up as they bake in the sun. Lighter-colored and deeper-grooved boards are more barefoot-friendly.

Doesn’t really look like wood: Some boards do a better job at mimicking wood than others, but a close look or touch gives them away.

Maintenance

Composites have few maintenance needs, so you’ll have plenty of time to take care of the ones that do crop up.

Clogs: Sweep or blow away any debris between the boards so that water can run off freely.

Food stains: Fast action is the best defense. Use a degreaser such as Dawn dish soap on oily spots, and bleach and hot water on fruit and wine stains. Placing mats around the barbecue is a good preventative measure.

Tannin stains: Scrub with cleaners that contain oxalic acid.

Gouges: Superficial scuff marks blend in over time, but any board that has deep scratches or melt marks will have to be replaced.

Mildew stains: Add some dish soap to a 50-50 mix of oxygen bleach and hot water.

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.

References:

  • https://www.thisoldhouse.com/decking/21018023/all-about-composite-decking
  • https://en.wikipedia.org/wiki/Composite_lumber#:~:text=Composite%20lumber%20is%20a%20material,%2C%20a%20wood%2Dplastic%20composite.
  • https://buildabroad.org/2017/02/22/wood-composite/
  • https://homeguides.sfgate.com/difference-between-wood-composite-veneer-laminate-100725.html
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