What is Use Class 4 Treatment?

Throughout the UK we use timber for a range of final applications, a lot of which end up in contact with the ground, timber products such as fence posts, for example.

Timber must be treated to Use Class 4 (UC4) standards if it regularly comes into contact with water and direct soil. This would include certain parts of a decking structure that will be sunk into the ground. Deck substructures have now been increased from UC3 to UC4 in accordance with WPA and WDCA regulations. 

WJ Timber Treatments are a certified timber treatment facility in the UK, servicing a range of timber products and species. We have multiple sites in the UK with both low and high pressure treatment capabilities. Our UC4 treatment is a high-pressure treatment protecting timber from rot, decay & insects.

The treatment process involves a high-pressure treatment tank and our protective treatment is applied to the cell structure of the timber. The below diagram shows the treatment process.



If you have a requirement for timber to be treated to Use Class 4, we’re a leading timber treatment supplier in the UK. We have high output capability, and our sites are operational 24 hours a day to cope with demand. We also have a dedicated fleet of HGVs capable of collecting and delivering customer’s timber throughout the UK and Ireland. 

Get in touch with our WJ Timber Treatments team today on 01482 338877 or email info@wj-group.co.uk.