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Campaign to promote 'fit for purpose' treated timber

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Is your treated timber 'fit for purpose'?

On-going campaign


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.

Results from ‘mystery shopper’ research sponsored by the 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.

British Standards for wood preservation – BS 8417 and the new WPA Code of Practice: Industrial Wood Preservation,  require that the loading and penetration of preservative impregnated into the wood is tailored to the desired end use.


Use Classes

Applications for treated wood are therefore grouped into Use Classes, the three main being: 

2, 3(u) and 4.

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Messaging to target markets

The challenge is how best to simplify this message whilst not losing technical accuracy. 


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 medium of the WPA’s Make Sure it’s 4 logo and communications package. 

For the broader timber supply chain, the focus also includes differentiating between interior and exterior applications for treated wood – using a bold, colour coded 'Use Class 2, 3 or 4?' message and simplified product descriptions. 

Please use and share any of the campaign assets below – to learn more and help raise awareness of the campaign.

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WPA-TTF Buyer's Guide to Treated Timber
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NEW Making the most of wood WEBINAR 2021

This short educational training webinar explains the principles involved with the correct specification and use of preservative treated wood.

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Focus on fencing

To further re-inforce the message that properly treated timber can be relied upon when performance in the field is paramount,  ' follow the Ground Rules'  – a trinity of requirements which ensures your fencing is fit for purpose.


Find a WPA Benchmark Approved Treater

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WPA TW 13 Installing Treated Fence Posts

Guidance Note TW13: Installing Preservative Treated Fence Posts 

All pre-treated wood products are impregnated in their finished form and are designed to be installed without modification.

This Guidance Note details, with simple illustrations, everything you should consider when preparing and installing both ROUND and SQUARE sawn softwood posts, pre-treated with a preservative for fencing applications.


Guidance Notes: Treated wood and Use Classes 2, 3 and 4 

For further information on what the most critical Use Classes mean in practice. 


They 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.

WPA TW 10 Understanding Use Class
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WPA TW 8 Understanding Use Class 4 2020-

Preservative Treatment Action Plan

Since 2017 The Timber Trade Federation (TTF) and the WPA have been working together to grow demand for preservative treated timber. They identified three priority areas for action, which have since been adopted as TTF policy:

  1. To address the common failure to specify treated wood correctly;

  2. To address the lack of understanding on how to correctly install and use treated wood;

  3. To ensure independent verification of the treatment process.


At the TTF AGM on 17 November 2020, members unanimously voted to implement this Preservative Treatment Action Plan into the TTF Code of ConductAs a result, Members must adhere to the guidance provided in BS8417 (2014) and the 2021 WPA Code of Practice: Industrial Wood Preservation for the choice, use, and application of wood preservatives.

Take a look around the

Resource Centre

FAQs - Manuals - Guidance Notes - Training

All of our resources are free to view and download. Please contact us if you have questions about any aspect of wood protection specification, quality assurance or application good practice.