Performance issues with wood plastic composite boards can be avoided, says TDCA

22 October 2015

The Timber Decking and Cladding Association (TDCA) has urged firms to do their research before buying wood plastic composite (WPC) deck boards and ensure they are installed in “strict compliance” with supplier guidance to avoid any issues with performance.

WPC deckboards are made from a mixture of plastic and wood flour and is a relatively new material in the UK, the organisation said. It has issued its warning after receiving reports of performance issues, which it said appear to be related to a particular type of hollow form WPC boards.
Installation errors were a feature in many cases although product quality issues remain unconfirmed. Concern has also arisen about new WPC deck boards being fitted over existing substructures.
“While we don’t currently cover WPC in membership, we acknowledge that WPC boards are often fitted onto a timber substructure and this aspect is very much within the domain of the association,” said Janet Sycamore, the TDCA’s director of operations.
“We recognise a need to educate people to ensure this critical part of the deck is built correctly with the capability to support the loads placed upon it. Also some of our DeckMark accredited members do have reputable WPC decking products on range.
“Furthermore we have been made aware of some projects where WPC deck boards are being retro fitted to existing timber substructures. This is fraught with potential pitfalls; in particular are the joist spans sufficient to support a different material with different properties? WPC boards simply do not have the same strength characteristics as timber.
“Wood plastic composites boards are made from a mixture of plastic and wood flour; these are materials with very different properties. Getting them to work together is not easy and there are critical elements at each stage in the manufacturing process that you must get right to ensure fitness for purpose. Any short cuts can lead to disastrous results. Reputable suppliers will ensure the products they source are manufactured with appropriate quality procedures in place”.
The message to anyone considering wood plastic composite decking, or any other product for that matter, is to heed the following advice:
• Ask for a copy of the suppliers installation guidance and follow it to the letter – if you don’t installation issues may mask any quality problems that may arise in service
• Closely examine any warranties given with the product. Check out what the warranty actually covers – is performance of the product covered for example?
• Ask about the process for making a claim
• Keep all your documents, communication exchanges and receipts safe for future reference
• Note dates and timings and start taking photographs if anything untoward begins to happen
• It’s worth checking if your house insurance policy covers legal assistance as it may help to finance a claim
The Timber Decking and Cladding Association offers advice on how to build a timber substructure for a wood plastic composite deck boards on its website at

Photo courtesy of TDCA: Trex Transcend, a solid form wood plastic composite, being fitted onto a timber substructure. Joists generally need to be closer together than with a real solid timber deck board. Credit: Arbor Forest Products Ltd