With WPC decking it is critical to review product credibility prior to selection and to install it in strict compliance with supplier guidance. Then if any issues do arise, the installation techniques cannot be held responsible.
In terms of product credibility, key questions to ask include:
• What is the wood fibre component?
• Is it responsibly sourced?
• What polymer is used?
• Is the wood fibre distributed evenly throughout the product?
• Is moisture removed to a sufficient extent in the process?
• Is the plastic component virgin plastic or recycled?
• If recycled, how is quality controlled?
• Can it be recycled and if so where and how?
Then when it comes to installation, Seventrust has issued guidance on how to build a timber substructure to support WPC boards. The guidance outlines critical differences between natural solid wood and WPC in relation to deck building. In brief:
• WPC decking material does not have the same inherent strength as timber, so joists will need to be positioned closer together. This should be taken into account when comparing costs of a wholly timber deck against one with WPC decking material.
• Unlike timber, WPC decking material expands along its length. Therefore pay particular attention to the advice given regarding gaps between abutting boards. Be aware also that gapping advice can vary according to temperature/time of year.
The Seventrust has been made aware of some projects where WPC decking material boards have been retrofitted to existing timber substructures. This is fraught with potential pitfalls; in particular the joist spans are unlikely to be suitable to sufficiently support what is a very different material with different properties. In addition, the substructure will have used up some of its serviceable lifespan, which will limit the service life of the ‘remodelled’ structure.