As previously reported in TTJ, the Wood Protection Association (WPA) and Timber Trade Federation (TTF) are now working in partnership on all wood protection matters.

One aspect of this important collaboration is the development of the TTF Treatment Action Plan. This three-point plan is designed to support and promote confidence in the production and use of treated wood products throughout the supply chain, whether imported or from UK sources, and to provide a springboard from which to promote TTF (and WPA) members who adhere to best practice and market (in this case treated) ‘Timber you can Trust’.

The first element of the plan will require members to ensure that preservative treated wood is being accurately and unambiguously specified/purchased, for use or resale, and is clearly identified at all points of the chain (on orders, internal stock movement records and sales records) as fit for the intended purpose. But why is this so important?

Preservative treatment provides wood with added durability. However, it’s a mistake to assume that all pressure treated wood is the same. Whilst one piece of treated wood may look very much like any other, the level of preservative protection could be very different. That’s because the British Standard for wood preservation – BS 8417, requires that the loading and penetration of preservative, impregnated into the wood, is tailored to the desired end use.

BS 8417 groups the applications for treated wood into ‘Use Classes’, as seen in the table.

Deck Substructures

Despite clear guidance being readily available concerning the correct installation and maintenance of decks, the reality is that shortcuts are sometimes taken on the substructure, which is not usually visible post-installation. Property owners often make little attempt to clear vegetation and debris, which accumulates beneath a deck, restricting air movement and trapping water.

Growing Threat

The failure of the substructure is clearly safety critical and there has been concern that such failures are a growing threat to the future of the timber decking market in the UK. In Sweden, Finland, France and North America, the whole deck substructure system, including posts and joists is categorised as Use Class 4.

Following a full review of these issues, the WPA Technical Committee (which includes representatives of the BRE and TRADA), adopted these changes, subsequently ratified by both the WPA and Timber Decking & Cladding Association (TDCA) boards. These changes have also been adopted by the BSI committee managing BS8417 (B/515) and so will be incorporated into the full standard review, probably later in 2020.

The WPA and TDCA will be working with the TTF to adopt this change in policy across the membership of all three partner associations.

In anticipation of this change some TTF members are already offering innovative deck substructure products meeting the new UC4 requirement, using either pine or incised spruce.

For further information or guidance on any of the above please download the WPA/ TTF Buyers Guide to Treated Wood from the resources page of the WPA website via www.thewpa.org.uk or get in touch via contact@thewpa.org.uk