Composite decking has been widely used in other parts of the world for decades, but it’s still relatively new in New Zealand.

Our high UV and relative humidity can wreak havoc on landscaping materials, traditional and modern.

There are a wide variety of composite materials available on the New Zealand market. But without thorough long-term testing and with a price tag considerably heftier than traditional decking materials, is it worth the risk?

Most composites are composed of wood waste or bamboo, fillers and plastic. They’re considered a low-maintenance, eco-friendly alternative building material for decks and other landscaping projects.

The wood grain patterns and colours of composite decking can be reasonably realistic.

The pros and cons

  • Composite decking never needs staining or sanding. But arguably, nor does modern treated timber.
  • Composite decking is widely accepted as being ‘good for the environment’. Some use recycled wood waste so no new trees must be felled. However, New Zealand’s pine forests are sustainably managed so we’re not exactly acting unsustainably by utilising natural timber.
  • Some manufacturers of composite decking use consumer waste plastic that would otherwise end up in landfills. Thinking long term though, both composite and traditional timber decking will eventually end up in the landfill. The traditional timber will biodegrade naturally, the composite not so well.
  • There are rumours about the scratch and gauge tendencies of some composite materials, with marks generally of a permanent and conspicuous nature. Yes, timber scratches too, but it also tends to expand and ‘heal’ itself of smaller scratches with a bit of time and rain. Scars may be seen to add character to natural timber. Whereas composites by nature lack rustic charm so rely heavily on a perfect facade to maintain their clean-cut characteristics.
  • Composite decking typically weighs more than timber and at the same time it is not as strong. As a result a stronger (more expensive) framing may be required. Composite decking is not a structural product but is usually installed over a frame of pressure treated lumber.
  • Most kiwi families enjoy a good sausage sizzle on the deck in summer. Hot coals can melt composite. Cooking grease can stain both composite and timber.
  • Replacing damaged boards retrospectively can be challenging with either material. Timber boards need to be unscrewed or prised off if nailed. But composite boards are often attached with hidden fasteners that can be difficult (or sometimes impossible) to replace individually.
  • Most composites have been engineered to be largely impermeable to water but it is still necessary to follow basic precautions to prevent mould. If mould or mildew develops it should be removed right away by cleaning with a solution designed for this purpose. Timber decking can be further treated to prevent mould if being used in dark or poorly ventilated areas. It can also be treated with mould and mildew remover such as Wet’n’Forget which is very effective and easy to use.
  • Composite decking is available in a limited variety of colours. Natural timber can be stained or painted in almost any colour.