Landscape and Urban Design Issue 45 2020 | Page 58

ASSOCIATION NEWS HOW DO YOU SPECIFY PRESERVATIVE TREATED WOOD? Recent ‘mystery shopper’ research sponsored by the UK Wood Protection Association (WPA) confirms that understanding amongst many users of preservative treated wood is very poor indeed. When asked if there was a specific treatment specification for timber in ground contact, over 90% of people surveyed said they didn’t know. When asked if they understood what ‘Use Class 4’ means, 72% said they didn’t know. So, how do YOU specify preservative treated wood?! 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. Applications for treated wood are therefore grouped into ‘Use Classes’, the three main being - The challenge is how best to simplify this message whilst not losing technical accuracy. Therefore, starting this summer, WPA has launched an educational campaign in partnership with the Timber Trade Federation (TTF) & the Timber Decking & Cladding Association (TDCA): For the fencing, garden and landscaping sector, the focus is on promoting the use of the term Use Class 4 for treated wood used in contact with or close to the ground, using the WPA’s ‘Make Sure it’s 4’ logo and communications package. James Jones Sawmills For those who need further guidance on what the most critical Use Classes mean in practice, WPA and TTF have developed three new A4 Guidance Notes on Understanding Use Class 2,3 & 4 preservative treated wood. These include a simple explanation of what national standards require for each application, what species are most suitable, what preservative penetration to expect in different treated commodities and the necessary quality control criteria. For those who wish to delve deeper, the WPA website www.thewpa.org. uk contains all you need to know. Any of the visuals and logos which accompany the Make Sure it’s 4 campaign are readily available, free of charge for all in the timber supply chain to use in their own promotional and educational resources. Simply get in touch via [email protected]. Treated Wood Specification & Installation Check List • Establish the Use Class of the timber you need, before ordering. • Tell your supplier in writing, that the wood must be treated to that particular Use Class to comply with BS 8417. Ask them to verify that the wood supplied meets your Use Class specification – on the delivery note and invoice or a treatment certificate. • When buying from stock always check to which Use Class the wood has been treated. • NEVER substitute wood that has been treated for an indoor application for use in an external application – failure is inevitable. • Do NOT supply wood that has been treated for external use for what you know will only be internal applications. • For wood in permanent ground or fresh water contact, or providing exterior structural support, Use Class 4 levels of protection MUST be achieved. Anything less and service life, structural safety and customer satisfaction will be compromised. • When cross cutting, notching or boring treated timber products during installation, ALWAYS apply an end grain preservative treatment to freshly exposed areas – to maintain the integrity of the protection. • NEVER put cut ends in the ground, even if end grain coated. To paraphrase a well known slogan, ‘Stay Alert: Control Treatment Quality: Protect your Business’! For further information or guidance on any of the above please download the new Guidance Notes on Use Classes 2, 3 & 4 and the WPA/ TTF Buyers Guide to Treated Wood from the resources page of the WPA website, free of charge, via www.thewpa.org.uk or give us a call. 58 www.landud.co.uk Follow us @ludmagazine